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Treatment of lung infection in patients with cystic fibrosis: Current and future strategies

Open ArchivePublished:November 08, 2012DOI:https://doi.org/10.1016/j.jcf.2012.10.004

      Abstract

      In patients with cystic fibrosis (CF) lung damage secondary to chronic infection is the main cause of death. Treatment of lung disease to reduce the impact of infection, inflammation and subsequent lung injury is therefore of major importance. Here we discuss the present status of antibiotic therapy for the major pathogens in CF airways, including prophylaxis against infection, eradication of early infection, suppression of chronic infection, and the treatment of infective exacerbations. We outline measures to optimize maintenance treatment for infection in the light of novel antibiotic drug formulations. We discuss new developments in culture-independent microbiological diagnostic techniques and the use of tools for monitoring the success of antibiotic treatment courses. Finally, cost-effectiveness analyses for antibiotic treatment in CF patients are discussed.

      1. Introduction

      Lung damage secondary to chronic infection is the main determinant of morbidity and mortality in individuals with cystic fibrosis (CF) [
      • Rosenfeld M.
      • Gibson R.L.
      • McNamara S.
      • Emerson J.
      • Burns J.L.
      • Castile R.
      • et al.
      Early pulmonary infection, inflammation, and clinical outcomes in infants with cystic fibrosis.
      ,
      • Emerson J.
      • Rosenfeld M.
      • McNamara S.
      • Ramsey B.
      • Gibson R.L.
      Pseudomonas aeruginosa and other predictors of mortality and morbidity in young children with cystic fibrosis.
      ]. CF individuals are highly susceptible to bacterial infections in the respiratory tract and repeated and intensive antibiotic therapy is required to maintain lung function and quality of life and reduce exacerbations in infected patients. Antibiotic therapy aimed at eradicating Pseudomonas aeruginosa, the major bacterial pathogen in CF, after early lung infection, and improved regimens to treat chronic P. aeruginosa infection have played a major role in the increasing median survival of CF patients during the last decades. In 1969 CF patients in industrialized countries had a mean survival of 14 years. By 2010 this had improved to more than 40 years [
      Cystic fibrosis foundation patient registry 2009 annual data report.
      ]. Sadly, this positive development has not been observed in all CF centers worldwide and median age at death is still in the 2nd/3rd decade. CF genotype, different approaches to care delivery including the treatment of infection, antibiotic selection and the mode of delivery, as well as health care resources and the socio-economic status of the patient [
      • Schechter M.S.
      • McColley S.A.
      • Silva S.
      • Haselkorn T.
      • Konstan M.W.
      • Wagener J.S.
      • et al.
      Association of socioeconomic status with the use of chronic therapies and healthcare utilization in children with cystic fibrosis.
      ,
      • McCormick J.
      • Mehta G.
      • Olesen H.V.
      Comparative demographics of the European cystic fibrosis population: a cross-sectional database analysis.
      ,
      • Taylor-Robinson D.
      • Whitehead W.
      • Diderichsen F.
      • Vebert Olesen H.
      • Pressler T.
      • Smyth R.S.
      • Diggle P.
      Understanding the natural progression in %FEV1 decline in patients with cystic fibrosis: a longitudinal study.
      ] may be responsible for the different outcomes.
      The objective of this consensus document is to provide guidance for current antibiotic treatment strategies for lung infections in CF. Here we discuss treatment courses for antibiotic eradication therapy (AET), including the window of opportunity in which this treatment option can be most successfully applied. We describe treatment strategies for chronic P. aeruginosa infection which cannot be eradicated with current antibiotics. Measures to optimize treatment in the light of new antibiotic drug formulations are considered and novel tools to determine the success of antibiotic treatment courses will be highlighted. In addition to P. aeruginosa, sputum specimens from CF patients generally contain many other bacterial species. We describe developments in diagnostic methods for their detection, the relevance of these pathogens for lung disease in CF patients and the impact this may have on therapeutic strategies. Finally, cost-effectiveness analyses for antibiotic treatment in CF patients are presented and recommendations are provided for important clinical questions. This consensus document updates related previous documents supported by ECFS [
      • Döring G.
      • Conway S.P.
      • Heijerman H.G.
      • Hodson M.E.
      • Hoiby N.
      • Smyth A.
      • et al.
      Antibiotic therapy against Pseudomonas aeruginosa in cystic fibrosis: a European consensus.
      ,
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ,
      • Heijerman H.
      • Westerman Elsbeth
      • Conway S.
      • Touw D.
      • Döring G.
      Inhaled medication and inhalation devices for lung disease in patients with cystic fibrosis: a European consensus.
      ].

      2. Current understanding of the pathophysiology of CF airways infection

      It is believed that the CF airways are not infected at birth and that opportunistically pathogenic bacteria enter the lower airways from the environment. These bacteria are able to eventually establish a chronic presence in the airways due to impaired innate immunity [
      • Döring G.
      • Gulbins E.
      Cystic fibrosis and innate immunity: how chloride channel mutations provoke lung disease.
      ] and are associated with a chronic inflammatory response. The bacteria most commonly believed to be pathogenic in CF include P aeruginosa, Staphylococcus aureus, Hemophilus influenzae, Stenotrophomonas maltophilia, Achromobacter xylosoxidans, and Burkholderia species [
      Cystic fibrosis foundation patient registry 2009 annual data report.
      ]. Recent microbiological studies have demonstrated that the infection of the CF airways is more complicated than demonstrated by standard culturing methods, and this will be discussed later. Although we believe the majority of these bacteria to be pathogenic, our understanding of how best to treat each of them remains incomplete. We know more about the pathogenesis and treatment of P. aeruginosa. Thus it will receive the most attention in these recommendations.
      P. aeruginosa enters the lower airways presumably by inhalation and may transiently infect the airways of some CF patients (range: ~10–50%); that is, it appears that some CF patients are able to clear the pathogen spontaneously, or more specifically, become culture-negative in subsequent specimens [
      • Burns J.L.
      • Gibson R.L.
      • McNamara S.
      • Yim D.
      • Emerson J.
      • Rosenfeld M.
      • et al.
      Longitudinal assessment of Pseudomonas aeruginosa in young children with cystic fibrosis.
      ,
      • Wiesemann H.G.
      • Steinkamp G.
      • Ratjen F.
      • Bauernfeind A.
      • Przyklenk B.
      • Döring G.
      • et al.
      Placebo-controlled, double-blind, randomized study of aerolized tobramycin for early treatment of Pseudomonas aeruginosa infection in cystic fibrosis.
      ,
      • Gibson R.L.
      • Emerson J.
      • McNamara S.
      • Burns J.L.
      • Rosenfeld M.
      • Yunker A.
      • et al.
      Significant microbiological effect of inhaled tobramycin in young children with cystic fibrosis.
      ,
      • Van Ewijk B.E.
      • Wolfs T.F.W.
      • Fleer A.
      • Kimpen J.L.L.
      • Van der Ent C.K.
      High Pseudomonas aeruginosa acquisition rate during acute respiratory infection in healthy and cystic fibrosis children.
      ]. However, the pathogen will persist or recur and eventually develop into a chronic infection, which is defined as repeatedly positive microbiological cultures and the presence of positive serum antibodies against the pathogen [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ] (Table 1). The Leeds definition [
      • Lee T.W.R.
      • Brownlee K.G.
      • Conway S.P.
      • Denton M.
      • Littlewood J.M.
      Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients.
      ] classifies patients into 4 groups according to airway culture results obtained over the last 12 months. “Chronic infection” refers to patients in whom more than 50% of the preceding 12 months P. aeruginosa was culture positive, and “intermittent infection” refers to patients with less than 50% of cultures positive for P. aeruginosa. A patient is defined as “free of P. aeruginosa” when no P. aeruginosa was grown from samples in the previous 12 months, despite a history of prior colonization with P. aeruginosa. “Never infected” refers to patients in whom P. aeruginosa has never been cultured. This definition has been evaluated in pediatric and adult CF populations and appears to classify patients appropriately with respect to clinical scores [
      • Lee T.W.R.
      • Brownlee K.G.
      • Conway S.P.
      • Denton M.
      • Littlewood J.M.
      Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients.
      ,
      • Proesmans M.
      • Balinska-Miskiewicz W.
      • Dupont L.
      • Bossuyt X.
      • Verhaegen J.
      • Høiby N.
      • et al.
      Evaluating the “Leeds criteria” for Pseudomonas aeruginosa infection in a cystic fibrosis centre.
      ]. This definition is useful but requires that frequent surveillance samples of sputum are taken and may not be pragmatic in clinical trials.
      Table 1Definition of relevant terms.
      Surveillance culturesPeriodic sampling of the upper or lower airways for the purpose of identifying the presence of a CF pathogen.
      ColonizationThe presence of pathogenic bacteria in the upper or lower airways in the absence of an inflammatory response.
      InfectionThe presence of pathogenic bacteria in the upper or lower airways associated with an inflammatory response.
      Spontaneous clearanceSubsequent culture of the CF upper or lower airways that is culture-negative when the previous cultures had been positive.
      Intermittent infection<50% of cultures are positive for the pathogen of interest
      • Lee T.W.R.
      • Brownlee K.G.
      • Conway S.P.
      • Denton M.
      • Littlewood J.M.
      Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients.
      .
      Chronic infection>50% of cultures are positive for the pathogen of interest; this may also be defined by the presence of serum antibodies or the observation of mucoidy
      • Lee T.W.R.
      • Brownlee K.G.
      • Conway S.P.
      • Denton M.
      • Littlewood J.M.
      Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients.
      .
      Free of P. aeruginosaWhen no P. aeruginosa was grown from samples in the previous 12 months, despite a history of prior colonization with P. aeruginosa
      • Lee T.W.R.
      • Brownlee K.G.
      • Conway S.P.
      • Denton M.
      • Littlewood J.M.
      Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients.
      .
      Never infected with

      P. aeruginosa
      Patients in whom P. aeruginosa has never been cultured
      • Lee T.W.R.
      • Brownlee K.G.
      • Conway S.P.
      • Denton M.
      • Littlewood J.M.
      Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients.
      .
      EradicationSubsequent cultures are free of the pathogen following treatment with antibiotics.
      Failure of eradicationSubsequent cultures are positive for the pathogen following treatment with antibiotics.
      Recurrence/re-infectionCultures of the upper or lower airways are again positive for the pathogen following a period where the patient was free of the pathogen following successful eradication.
      Chronic infection results in a prolonged inflammatory response, which is believed to cause respiratory tissue injury leading to progressive loss of lung function. There is sufficient evidence that eradication of early infection and prevention of chronic infection is associated with clinical benefit. In general young CF patients without P. aeruginosa infection and those undergoing AET have preserved lung function (by spirometry), which only marginally decreased over years in contrast to CF patients with chronic P. aeruginosa infection [
      • Taccetti G.
      • Campana S.
      • Festini F.
      • Mascherini M.
      • Döring G.
      Early eradication therapy against Pseudomonas aeruginosa in cystic fibrosis patients.
      ,
      • Kozlowska W.J.
      • Bush A.
      • Wade A.
      • Aurora P.
      • Carr S.B.
      • Castle R.A.
      • et al.
      Lung function from infancy to the preschool years after clinical diagnosis of cystic fibrosis.
      ]. For example, the decline in “forced expiratory volume in 1 s% predicted” (FEV1%) in CF patients who had received AET was less compared to that in chronically infected patients (ΔFEV1/year: −1.65% vs. −4.74%) [
      • Taccetti G.
      • Campana S.
      • Festini F.
      • Mascherini M.
      • Döring G.
      Early eradication therapy against Pseudomonas aeruginosa in cystic fibrosis patients.
      ]. AET studies that have followed patients up to 18 months did not observe a lung function decline [
      • Ratjen F.
      • Munck A.
      • Kho P.
      • Angyalosi G.
      ELITE Study Group. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial.
      ,
      • Treggiari M.M.
      • Retsch-Bogart G.
      • Mayer-Hamblett N.
      • Khan U.
      • Kulich M.
      • Kronmal R.
      • et al.
      Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ]. In a retrospective analysis of the Toronto data base, patients who cleared P. aeruginosa after first infection had a similar lung function decline over the subsequent years as those who had never been infected [
      • Amin R.
      • Lam M.
      • Dupuis A.
      • Ratjen F.
      The effect of early Pseudomonas aeruginosa treatment on lung function in pediatric cystic fibrosis.
      ]. In studies of antibiotic treatment of early airways infection, the failure to eradicate the P. aeruginosa was associated with an increased risk of pulmonary exacerbation and persistent P. aeruginosa infection was associated with even a greater risk of exacerbation [
      • Mayer-Hamblett N.
      • Kronmal R.A.
      • Gibson R.L.
      • Rosenfeld M.
      • Retsch-Bogart G.
      • Treggiari M.M.
      • et al.
      Initial Pseudomonas aeruginosa treatment failure is associated with exacerbations in cystic fibrosis.
      ], further raising the concern that persistent or recurrent infection has a negative impact on lung health. P. aeruginosa acquisition is associated with further deterioration in lung function in CF, even when the pathogen is eradicated [
      • Kozlowska W.J.
      • Bush A.
      • Wade A.
      • Aurora P.
      • Carr S.B.
      • Castle R.A.
      • et al.
      Lung function from infancy to the preschool years after clinical diagnosis of cystic fibrosis.
      ], suggesting that airflow obstruction of uncomplicated CF needs to be treated, and rigorous strategies to prevent P. aeruginosa acquisition should be implemented.

      3. Current status of antibiotic prophylaxis for P aeruginosa

      As P. aeruginosa infection of the CF airways may not cause symptoms and may develop into chronic infection that cannot be eradicated, then can prophylactic administration of antipseudomonal antibiotics be beneficial in the prevention of chronic airways infection by P. aeruginosa? A prospective 3-year study compared the effect of prophylactic oral ciprofloxacin and inhaled colistin treatment with placebo on prevention of initial P. aeruginosa infection in children with CF [
      • Tramper-Stranders G.A.
      • van der Ent C.K.
      • Molin S.
      • Yang L.
      • Hansen S.K.
      • Rau M.H.
      • et al.
      Initial Pseudomonas aeruginosa infection in patients with cystic fibrosis: characteristics of eradicated and persistent isolates.
      ]. No difference in the rate of acquisition of P. aeruginosa was observed between the control and treatment groups, although P. aeruginosa antibodies emerged earlier in the control group. The authors concluded that a three-monthly cycled prophylactic antibiotic therapy would not reduce the risk of initial P. aeruginosa infection in children with CF. The risks for selecting other pathogens, the time commitment, and the lack of cost efficacy for this strategy may prevent further studies with similar designs. Thus, the current data suggest that prophylactic treatment with antipseudomonal antibiotics are not recommended to prevent P. aeruginosa infections in CF patients. Of note, alternative strategies for primary or secondary prevention have been evaluated [
      • Döring G.
      • Meisner C.
      • Stern M.
      for the Flagella Vaccine Trial Study Group
      A double-blind randomized placebo-controlled phase III study of a Pseudomonas aeruginosa flagella vaccine in cystic fibrosis patients.
      ] or are under evaluation (gargling of avian anti-Pseudomonas IgY antibodies; EUDRACT-2011-000801-39).

      4. Current status of antibiotic eradication therapy for P. aeruginosa

      There is strong published evidence that rigorous antibiotic treatment of early P. aeruginosa colonization/infection is beneficial for CF patients because it has a significantly high eradication rate [
      • Gibson R.L.
      • Emerson J.
      • McNamara S.
      • Burns J.L.
      • Rosenfeld M.
      • Yunker A.
      • et al.
      Significant microbiological effect of inhaled tobramycin in young children with cystic fibrosis.
      ] and keeps the lower airways free of this pathogen for longer periods compared to patients who are not treated. AET is now routinely recommended in many countries and the success of various regimens has been documented [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ,
      • Ratjen F.
      • Munck A.
      • Kho P.
      • Angyalosi G.
      ELITE Study Group. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial.
      ,
      • Treggiari M.M.
      • Retsch-Bogart G.
      • Mayer-Hamblett N.
      • Khan U.
      • Kulich M.
      • Kronmal R.
      • et al.
      Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ,
      • Cantón R.
      • Cobos N.
      • De Gracia J.
      • Baquero F.
      • Honorato J.
      • Gartner S.
      Antimicrobial therapy of pulmonary pathogenic colonisation and infection by Pseudomonas aeruginosa in cystic fibrosis patients.
      ]. Thus, AET for P. aeruginosa is recommended in CF. Although there is evidence that in some patients a positive culture may be transient, in most patients P. aeruginosa will persist. Considering that a risk/benefit ratio favors AET, it seems reasonable to initiate AET as soon as possible after a positive P. aeruginosa respiratory culture. However, there is currently no specific treatment strategy for the eradication of P. aeruginosa that has been recommended. Thus, what is the best strategy of antibiotic therapy for eradication of P. aeruginosa?
      The success rates to eradicate P. aeruginosa in different AET studies [
      • Wiesemann H.G.
      • Steinkamp G.
      • Ratjen F.
      • Bauernfeind A.
      • Przyklenk B.
      • Döring G.
      • et al.
      Placebo-controlled, double-blind, randomized study of aerolized tobramycin for early treatment of Pseudomonas aeruginosa infection in cystic fibrosis.
      ,
      • Gibson R.L.
      • Emerson J.
      • McNamara S.
      • Burns J.L.
      • Rosenfeld M.
      • Yunker A.
      • et al.
      Significant microbiological effect of inhaled tobramycin in young children with cystic fibrosis.
      ,
      • Taccetti G.
      • Campana S.
      • Festini F.
      • Mascherini M.
      • Döring G.
      Early eradication therapy against Pseudomonas aeruginosa in cystic fibrosis patients.
      ,
      • Ratjen F.
      • Munck A.
      • Kho P.
      • Angyalosi G.
      ELITE Study Group. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial.
      ,
      • Treggiari M.M.
      • Retsch-Bogart G.
      • Mayer-Hamblett N.
      • Khan U.
      • Kulich M.
      • Kronmal R.
      • et al.
      Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ,
      • Valerius N.H.
      • Koch C.
      • Høiby N.
      Prevention of chronic Pseudomonas aeruginosa colonisation in cystic fibrosis by early treatment.
      ,
      • Ratjen F.
      • Döring G.
      • Nikolaizik W.H.
      Effect of inhaled tobramycin on early Pseudomonas aeruginosa colonisation in patients with cystic fibrosis.
      ,
      • Gibson R.L.
      • Emerson J.
      • Mayer-Hamblett N.
      • Burns J.L.
      • McNamara S.
      • Accurso F.J.
      • et al.
      Duration of treatment effect after tobramycin solution for inhalation in young children with cystic fibrosis.
      ,
      • Taccetti G.
      • Bianchini E.
      • Cariani L.
      • Buzzetti R.
      • Costantini D.
      • Trevisan F.
      Early antibiotic treatment for Pseudomonas aeruginosa eradication in patients with cystic fibrosis: a randomised multicentre study comparing two different protocols.
      ] ranges between 63% and 100% (mean: 81.2%). In the open-label, randomized ELITE trial [
      • Ratjen F.
      • Munck A.
      • Kho P.
      • Angyalosi G.
      ELITE Study Group. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial.
      ], which compared the efficacy and safety of 2 regimens (28 and 56 days) of 300 mg twice daily tobramycin inhalation solution (TIS), >90% of patients in both groups had negative cultures for P. aeruginosa 1 month after the end of treatment and the majority of these patients remained free from infection for up to 27 months. The median time to recurrence of P. aeruginosa in patients' sputum/cough swab was similar in the 2 cohorts. In the EPIC study [
      • Treggiari M.M.
      • Retsch-Bogart G.
      • Mayer-Hamblett N.
      • Khan U.
      • Kulich M.
      • Kronmal R.
      • et al.
      Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ], 304 children, aged 1–12 years, were randomized to 1 of 4 eradication treatment regimens for 18 months. The participants, randomized to cycled therapy, received TIS (300 mg twice a day) for 28 days, with either oral ciprofloxacin (15–20 mg/kg twice a day) or oral placebo for 14 days every quarter, while the participants randomized to the culture-based therapy received the same treatment only during quarters with a positive P. aeruginosa culture. There was no statistically significant difference between all groups in the proportion of P. aeruginosa positive cultures throughout the study period. Thus, adding ciprofloxacin produced no further benefits nor did routine periodic treatment even in the absence of positive cultures [
      • Treggiari M.M.
      • Retsch-Bogart G.
      • Mayer-Hamblett N.
      • Khan U.
      • Kulich M.
      • Kronmal R.
      • et al.
      Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ].
      The combination of inhaled colistin for 3 weeks–3 months of treatment plus oral ciprofloxacin has been used successfully [
      • Høiby N.
      • Frederiksen B.
      • Pressler T.
      Eradication of early Pseudomonas aeruginosa infection.
      ]. The efficacy of the combination of ciprofloxacin and inhaled colistin for 3 months compared to TIS for 1 month to eradicate early P. aeruginosa infection was compared in a real-life setting and was similar in outcomes [

      Proesmans M. Comparison of two treatment regimens for eradication of P aeruginosa infection in children with cystic fibrosis. J Cyst Fibros in press.

      ]. Furthermore, when CF patients were assigned to inhaled colistin/oral ciprofloxacin or to inhaled tobramycin/oral ciprofloxacin no differences in outcome between the two arms were observed [
      • Taccetti G.
      • Bianchini E.
      • Cariani L.
      • Buzzetti R.
      • Costantini D.
      • Trevisan F.
      Early antibiotic treatment for Pseudomonas aeruginosa eradication in patients with cystic fibrosis: a randomised multicentre study comparing two different protocols.
      ]. Intravenously administered antibiotics have also been used in AET protocols [
      • Lillquist Y.P.
      • Cho E.
      • Davidson A.G.
      Economic effects of an eradication protocol for first appearance of Pseudomonas aeruginosa in cystic fibrosis patients: 1995 vs. 2009.
      ]. In a trial comparing oral/inhaled versus intravenous therapy, decreased lung inflammation was observed in the latter group [
      • Noah T.L.
      • Ivins S.S.
      • Abode K.A.
      • Stewart P.W.
      • Michelson P.H.
      • Harris W.T.
      • et al.
      Inhaled versus systemic antibiotics and airway inflammation in children with cystic fibrosis and Pseudomonas.
      ].
      Although various AET protocols have demonstrated success, none have shown clear superiority. Thus the clinician may choose the treatment strategy that has been shown to be the most convenient with the same degree of success. Safety issues must also be taken into account. AET with TIS appears to be safe in young patients and not to cause the adverse effects seen with recurrent parenteral administration of aminoglycosides [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ,
      • Kumana C.R.
      • Yuen K.Y.
      Parenteral aminoglycoside therapy. Selection, administration and monitoring.
      ]. Recent European Guidelines recommend the inclusion of data from very young children in clinical studies [CHMP Guideline on the clinical development of medicinal products for the treatment of CF, 2011]. In patients aged 6 months to 6 years with normal renal function, systemic exposure following inhalation of 300 mg/5 mL of TIS was safe [
      • Rosenfeld M.
      • Gibson R.
      • McNamara S.
      • Emerson J.
      • McCoyd K.S.
      • Shell R.
      • et al.
      Serum and lower respiratory tract drug concentrations produced by tobramycin for inhalation in young children with cystic fibrosis.
      ]. The use of the same doses of TIS from infancy to adulthood is supported by the ELITE trial [
      • Ratjen F.
      • Munck A.
      • Kho P.
      • Angyalosi G.
      ELITE Study Group. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial.
      ] and in the EPIC trial [
      • Treggiari M.M.
      • Retsch-Bogart G.
      • Mayer-Hamblett N.
      • Khan U.
      • Kulich M.
      • Kronmal R.
      • et al.
      Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ]. A double-blind randomized multi-national study is currently ongoing, which includes patients aged 3 months to 7 years with the aim to provide regulatory-grade evidence of the efficacy and safety of TIS (EUDRACT-2011-002000-32). Thus, the current data suggest that 28days of TIS when there is a positive culture is a recommended treatment strategy for the purpose of eradication of P. aeruginosa. However, because a number of treatment protocols have been shown to be of similar effectiveness including oral, inhalation and intravenous therapy, and there are only few comparative studies available, the optimal antibiotic regimen is not known.

      4.1 Why is AET not always successful?

      Although AET has shown mean eradication rates of 81.2%, there are some patients for whom this strategy fails (definition Table 1). There are potential patient and pathogen factors that may limit the ability of AET to eradicate P. aeruginosa from CF airways. First, the patient must be adherent to the treatment regimen in order for it to be successful. Timing may be critical as there may be a window of opportunity after which AET will not be successful. Although several studies suggest that eradication of P. aeruginosa from CF airways by AET is most successful up to 12 weeks from initial detection [
      • Hansen C.R.
      • Pressler T.
      • Høiby N.
      Early aggressive eradication therapy for intermittent Pseudomonas aeruginosa airway infection in cystic fibrosis patients: 15 years experience.
      ,
      • Treggiari M.M.
      • Rosenfeld M.
      • Retsch-Bogart G.
      • Gibson R.
      • Ramsey B.
      Approach to eradication of initial Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ], this period is not well defined and further studies are needed to better define early, intermittent and chronic P. aeruginosa infection (Table 1). Many factors impair the efficacy of antimicrobial drugs and preclude the eradication of P. aeruginosa in CF, once the infection is chronically established in the patients' airways [
      • Rogers G.B.
      • Hoffman L.R.
      • Döring G.
      Novel concepts in evaluating antimicrobial therapy for bacterial lung infections in patients with cystic fibrosis.
      ,
      • Høiby N.
      • Ciofu O.
      • Bjarnsholt T.
      Pseudomonas aeruginosa biofilms in cystic fibrosis.
      ,
      • del Pozo J.L.
      • Patel R.
      The challenge of treating biofilm-associated bacterial infections.
      ]. These include bacterial [
      • Høiby N.
      • Ciofu O.
      • Bjarnsholt T.
      Pseudomonas aeruginosa biofilms in cystic fibrosis.
      ,
      • Smith E.E.
      • Buckley D.G.
      • Wu Z.
      • Saenphimmachak C.
      • Hoffman L.R.
      • D'Argenio D.A.
      • et al.
      Genetic adaptation by Pseudomonas aeruginosa to the airways of cystic fibrosis patients.
      ,
      • Foweraker J.E.
      • Laughton C.R.
      • Brown D.F.
      • Bilton D.
      Comparison of methods to test antibiotic combinations against heterogeneous populations of multiresistant Pseudomonas aeruginosa from patients with acute infective exacerbations in cystic fibrosis.
      ,
      • Döring G.
      • Parameswaran G.I.
      • Murphy T.F.
      Differential adaptation of microbial pathogens to airways of patients with cystic fibrosis and chronic obstructive pulmonary disease.
      ,
      • Mulcahy L.R.
      • Burns J.L.
      • Lory S.
      • Lewis K.
      Emergence of Pseudomonas aeruginosa strains producing high levels of persister cells in patients with cystic fibrosis.
      ,
      • Høiby N.
      • Bjarnsholt T.
      • Givskov M.
      • Molin S.
      • Ciofu O.
      Antibiotic resistance of bacterial biofilms.
      ,
      • Bjarnsholt T.
      • Østrup Jensen P.
      • Jakobsen T.H.
      • Phipps R.
      • Nielsen A.K.
      • Rybtke M.T.
      • et al.
      Quorum sensing and virulence of Pseudomonas aeruginosa during lung infection of cystic fibrosis patients.
      ,
      • Mowat E.
      • Paterson S.
      • Fothergill J.L.
      • Wright E.A.
      • Ledson M.J.
      • Walshaw M.J.
      • et al.
      Pseudomonas aeruginosa population diversity and turnover in cystic fibrosis chronic infections.
      ] and host factors [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ,
      • Döring G.
      • Gulbins E.
      Cystic fibrosis and innate immunity: how chloride channel mutations provoke lung disease.
      ,
      • Ordonez C.L.
      • Henig N.R.
      • Mayer-Hamblett N.
      • Accurso F.J.
      • Burns J.L.
      • Chmiel J.F.
      • et al.
      Inflammatory and microbiologic markers in induced sputum after intravenous antibiotics in cystic fibrosis.
      ,
      • Ciofu O.
      • Mandsberg L.
      • Bjarnsholt T.
      • Wassermann T.
      • Høiby N.
      Genetic adaptation of P. aeruginosa during chronic lung infection of patients with cystic fibrosis: strong and weak mutators with heterogenous genetic backgrounds emerge in mucA and/or lasR mutants.
      ,
      • Yang L.
      • Jelsbak L.
      • Marvig R.L.
      • Damkiæra S.
      • Workmana C.T.
      • Rau M.H.
      • et al.
      Evolutionary dynamics of bacteria in a human host environment.
      ].
      It is not known whether CF patients who fail to eradicate P. aeruginosa after AET have more lung inflammation and/or lung tissue injury due to the underlying CF defect or as a consequence of bacterial infections with pathogens other than P. aeruginosa. Maintenance of the CF patient's lung function over extended periods of time in the presence of the persistent pathogen in the airways is therefore a key in the antibiotic management of chronic P. aeruginosa lung infection. Peripheral distribution of aerosolized medications is reduced in the presence of airway obstruction, so drug may not get to the site of infection.
      It is also possible that there is successful eradication of infection from the lower airways, but there is rapid re-infection. The source of the original infection may be the sinonasal cavities, which may not be reached by inhaled antibiotics. A cross-sectional study showed frequently different microorganisms cultured from oral swab, sinus and BAL fluid [
      • Muhlebach M.S.
      • Miller M.B.
      • Moore C.
      • Wedd J.P.
      • Drake A.F.
      • Leigh M.W.
      Are lower airway or throat cultures predictive of sinus bacteriology in cystic fibrosis?.
      ] which makes it unlikely that the sinonasal cavities initiate lower bacterial lung infections in CF. However, other studies contradict this hypothesis [
      • Mainz J.G.
      • Hentschel J.
      • Schien C.
      • Cramer N.
      • Pfister W.
      • Beck J.F.
      • et al.
      Sinonasal persistence of Pseudomonas aeruginosa after lung transplantation.
      ,
      • Hansen S.K.
      • Rau M.H.
      • Johansen H.K.
      • Ciofu O.
      • Jelsbak L.
      • Yang L.
      • et al.
      Evolution and diversification of Pseudomonas aeruginosa in the paranasal sinuses of cystic fibrosis children have implications for chronic lung infection.
      ,

      Johansen HK, Aanaes K, Pressler T, et al. Colonization and infection of the paranasal sinuses in cystic fibrosis patients is accompanied by a reduced PMN response. J Cyst Fibros in press, http://dx.doi.org/10.1016/j.jcf.2012.04.011.

      ].
      Finally, it is recognized that culture negativity following AET does not necessarily mean that the pathogen was eradicated. It may be possible that the pathogen persists, though undetectable, after AET in the CF airways [
      • Munck A.
      • Bonacorsi S.
      • Mariani-Kurkdjian P.
      • Lebourgeois M.
      • Gérardin M.
      • Brahimi N.
      • et al.
      Genotypic characterization of Pseudomonas aeruginosa strains recovered from patients with cystic fibrosis afterinitial and subsequent colonization.
      ]. It is not known if there is a means of detecting the difference between true eradication and suppression of the numbers of the viable pathogen. A serological analysis of the EPIC AET study suggests that positive serology in CF patients identified the participants at higher risk for re-infection with P. aeruginosa after AET and identified CF individuals who failed to clear P. aeruginosa infection [

      Anstead, M, Heltshe S, Khan U, et al. Pseudomonas aeruginosa serology and risk for re-isolation in the EPIC trial. J Cyst Fibros in press, http://dx.doi.org/10.1016/j.jcf.2012.08.001.

      ]. Given the fact that AET is considered to be the standard of care in CF, observational studies are the only way to assess the long-term effect of this intervention. It is important to determine whether patients who have successfully eradicated P. aeruginosa after AET courses, differ with regard to lung function from those patients who never had episodes of P. aeruginosa infections and such studies should be designed. Thus, the current data suggest that a number of different reasons are responsible for the observation that eradication therapy is not successful.

      4.2 What is the best next strategy for the patient who has failed AET?

      The potential failure of AET argues for optimal surveillance of P. aeruginosa in respiratory cultures (see Section 7) in order to know when alternative treatment options are needed. In the EPIC trial, the subjects who did not clear P. aeruginosa after 3 weeks of treatment of the first cycle were further treated for 28 days with the study drug. The rate of treatment failure was low (unpublished data) suggesting that repeating the initial AET is reasonable. For those who have failed a second attempt at eradication using inhaled and/or oral antibiotics, systemic treatment with intravenous antibiotics may be tried. The scheme depicted in Fig. 1 is proposed as a potential care scheme for patients undergoing AET.
      Figure thumbnail gr1
      Fig. 1The Artimino Algorithm for antibiotic eradication therapy (AET). Scheme for treatment of persistent P. aeruginosa following an initial AET intervention (+ve: positive; −ve: negative).

      5. Optimizing antibiotic therapy for treatment of chronic P. aeruginosa infections

      Although AET has considerably decreased the prevalence of P. aeruginosa in younger CF patients, the pathogen is still present in the majority of older CF patients [
      Cystic fibrosis foundation patient registry 2009 annual data report.
      ,
      • McCormick J.
      • Mehta G.
      • Olesen H.V.
      Comparative demographics of the European cystic fibrosis population: a cross-sectional database analysis.
      ,
      • Bellis G.
      • Cazes M.H.
      • Parant A.
      • Gaimard M.
      • Travers C.
      • Le Roux E.
      • et al.
      Cystic fibrosis mortality trends in France.
      , ]. Chronic suppressive antibiotics have proven successful as a treatment of chronic airways infection in the maintenance of lung health [
      • Flume P.A.
      • O'Sullivan B.P.
      • Robinson K.A.
      • Goss C.H.
      • Mogayzel Jr, P.J.
      • Willey-Courand D.B.
      • et al.
      Cystic fibrosis pulmonary guidelines. Chronic medications for maintenance of lung health.
      ]. Tobramycin inhalation solution (TIS, Novartis) was the first approved inhaled antibiotic, but since then there are a number of new formulations developed for the treatment of P. aeruginosa infections in CF patients.

      5.1 Approved aerosol antibiotics

      5.1.1 Tobramycin

      Tobramycin is an aminoglycoside antibiotic that has long been used as an aerosol therapy for CF. TIS was the first aerosol antibiotic approved for CF and has been a workhorse chronic medication and is included in the CF treatment guidelines [
      • Flume P.A.
      • O'Sullivan B.P.
      • Robinson K.A.
      • Goss C.H.
      • Mogayzel Jr, P.J.
      • Willey-Courand D.B.
      • et al.
      Cystic fibrosis pulmonary guidelines. Chronic medications for maintenance of lung health.
      ,
      • Flume P.A.
      • Mogayzel P.J.
      • Robinson K.A.
      • Rosenblatt R.L.
      • Quittell L.
      • Marshall B.C.
      • et al.
      Cystic fibrosis pulmonary guidelines: treatment of pulmonary exacerbations.
      ,
      • Ryan G.
      • Singh M.
      • Dwan K.
      Inhaled antibiotics for long-term therapy in cystic fibrosis.
      ] for the suppression of P. aeruginosa infection, resulting in improved lung function and prevention of pulmonary exacerbations. The approved dose is 300 mg nebulized twice daily every other month. TIS is available in most countries.
      Tobramycin is also available in another nebulized formulation (Bramitob®, Chiesi) [
      • Chuchalin A.
      • Csiszér E.
      • Gyurkovics K.
      • Bartnicka M.T.
      • Sands D.
      • Kapranov N.
      • et al.
      Formulation of aerosolized tobramycin (Bramitob) in the treatment of patients with cystic fibrosis and Pseudomonas aeruginosa infection: a double-blind, placebo-controlled, multicenter study.
      ]. The total dose is the same as for TIS, but it is more concentrated (75 mg/mL versus 60 mg/mL) to decrease nebulization time. In a double-blind randomized study, 247 CF patients with chronic P. aeruginosa infection were randomized to receive nebulized 300 mg/4 mL tobramycin or placebo over a 24-week study period in 4-week on and off cycles. At week 20, FEV1 was significantly increased in the intention-to-treat population versus placebo. Treatment induced a trend toward decreased hospitalizations, increased nutritional status, and was well tolerated. The approved dose is 300 mg nebulized twice daily every other month. Bramitob is currently available only in European countries.
      Tobramycin has also been developed as a dry powder formulation (TOBI® Podhaler®, TIP™, Novartis) for the management of chronic P. aeruginosa infection in CF patients. Tobramycin inhalation powder (TIP) capsules are formed of low density porous particles (PulmoSphere™), which exhibit improved flow and dispersion by inhalation via the passive T-326 dry powder inhaler (Podhaler). The dose was developed to replicate the pharmacokinetics of TIS [
      • Geller D.E.
      • Konstan M.W.
      • Smith J.
      • Noonberg S.B.
      • Conrad C.
      Novel tobramycin inhalation powder in cystic fibrosis subjects: pharmacokinetics and safety.
      ]. Two controlled studies investigated the efficacy and safety of TOBI Podhaler. The EAGER trial enrolled 553 CF patients comparing TIP to TIS over 3 cycles of treatment [
      • Konstan M.W.
      • Flume P.A.
      • Kappler M.
      • Chirond R.
      • Higgins M.
      • Brockhaus F.
      • et al.
      Safety, efficacy and convenience of tobramycin inhalation powder in cystic fibrosis patients: the EAGER trial.
      ]. The EVOLVE trial, including 102 CF patients [
      • Konstan M.W.
      • Geller D.E.
      • Minić P.
      • Brockhaus F.
      • Zhang J.
      • Angyalosi G.
      Tobramycin inhalation powder for P. aeruginosa infection in cystic fibrosis: the EVOLVE trial.
      ], was placebo-controlled for 1 cycle followed by open label treatment with the TOBI Podhaler for 2 additional cycles of treatment. The Podhaler formulation displayed similar tolerability and efficacy to TIS and significantly improved FEV1 compared with placebo. Cough was the most frequently reported adverse reaction related to the dry powder in both clinical studies. The recommended dose is 112 mg (four 28 mg capsules) inhaled twice daily in alternating cycles of 28 days on treatment followed by 28 days off treatment. TIP is currently available in some European countries, South America, and Canada.

      5.2 Aztreonam lysine for inhalation

      The nebulized monobactam aztreonam lysine inhalation solution (AZLI, Cayston®, Gilead) was approved in 2010 for improvement of respiratory symptoms in CF patients 6 years old and over with chronic P. aeruginosa infection. Cayston® is delivered via the PARI eFlow platform through a portable Altera handset which controls particle size for optimal airway deposition, minimizes delivery time, and increases particle delivery efficiency. Inhalation time in clinical trials averaged 2 min for each 75 mg dose [
      • McCoy K.S.
      • Quittner A.L.
      • Oermann C.M.
      • Gibson R.L.
      • Retsch-Bogart G.Z.
      • Montgomery A.B.
      Inhaled aztreonam lysine for chronic airway Pseudomonas aeruginosa in cystic fibrosis.
      ,
      • Retsch-Bogart G.Z.
      • Quittner A.L.
      • Gibson R.L.
      • Oermann C.M.
      • McCoy K.S.
      • Montgomery A.B.
      • et al.
      Efficacy and safety of inhaled aztreonam lysine for airway pseudomonas in cystic fibrosis.
      ]. The recommended dose is 75 mg inhaled thrice daily, with a minimum of four hours between doses, in alternating cycles of 28 days on treatment followed by 28 days off treatment.
      In several clinical studies Cayston® has been shown to be safe and efficacious in suppressing chronic P. aeruginosa lung infection in CF patients [
      • McCoy K.S.
      • Quittner A.L.
      • Oermann C.M.
      • Gibson R.L.
      • Retsch-Bogart G.Z.
      • Montgomery A.B.
      Inhaled aztreonam lysine for chronic airway Pseudomonas aeruginosa in cystic fibrosis.
      ,
      • Retsch-Bogart G.Z.
      • Quittner A.L.
      • Gibson R.L.
      • Oermann C.M.
      • McCoy K.S.
      • Montgomery A.B.
      • et al.
      Efficacy and safety of inhaled aztreonam lysine for airway pseudomonas in cystic fibrosis.
      ,
      • Oermann C.M.
      • Retsch-Bogart G.Z.
      • Quittner A.L.
      • Gibson R.L.
      • McCoy K.S.
      • Montgomery A.B.
      • et al.
      An 18-month study of the safety and efficacy of repeated courses of inhaled aztreonam lysine in cystic fibrosis.
      ,
      • Wainwright C.E.
      • Vidmar S.
      • Armstrong D.S.
      • Byrnes C.A.
      • Carlin J.B.
      • Cheney J.
      • et al.
      Effect of bronchoalveolar lavage-directed therapy on Pseudomonas aeruginosa infection and structural lung injury in children with cystic fibrosis: a randomized trial.
      ]. In a randomized, placebo-controlled study of 164 CF patients [
      • Retsch-Bogart G.Z.
      • Quittner A.L.
      • Gibson R.L.
      • Oermann C.M.
      • McCoy K.S.
      • Montgomery A.B.
      • et al.
      Efficacy and safety of inhaled aztreonam lysine for airway pseudomonas in cystic fibrosis.
      ], Cayston significantly improved CFQ-R Respiratory Symptoms Score (RSS) and FEV1 after one cycle of use at 28 days, with a treatment difference compared to placebo of 9.7 points and 10.3%, respectively. In a second pivotal trial of 211 patients with CF [
      • McCoy K.S.
      • Quittner A.L.
      • Oermann C.M.
      • Gibson R.L.
      • Retsch-Bogart G.Z.
      • Montgomery A.B.
      Inhaled aztreonam lysine for chronic airway Pseudomonas aeruginosa in cystic fibrosis.
      ], Cayston increased the median time to need for additional antipseudomonal antibiotics for symptoms of pulmonary exacerbation by 21 days, versus placebo. In the open-label follow-on study of these two trials, Cayston safety and efficacy was examined in 274 patients over 18 [
      • Oermann C.M.
      • Retsch-Bogart G.Z.
      • Quittner A.L.
      • Gibson R.L.
      • McCoy K.S.
      • Montgomery A.B.
      • et al.
      An 18-month study of the safety and efficacy of repeated courses of inhaled aztreonam lysine in cystic fibrosis.
      ]. FEV1 values, CFQ-R RSS, and body weight increased with each 28 day course of Cayston, and this effect was maintained over 18 months. No significant safety concerns were observed in studies over 12 months [

      Assael BM, Pressler T, Bilton D, Fayond M, Fischer R, Chiron R, et al. Inhaled aztreonam lysine vs. inhaled tobramycin in cystic fibrosis: A comparative efficacy trial. J Cyst Fibros in press, http://dx.doi.org/10.1016/j.jcf.2012.07.006.

      ] and 18 months [
      • Oermann C.M.
      • Retsch-Bogart G.Z.
      • Quittner A.L.
      • Gibson R.L.
      • McCoy K.S.
      • Montgomery A.B.
      • et al.
      An 18-month study of the safety and efficacy of repeated courses of inhaled aztreonam lysine in cystic fibrosis.
      ]; including no evidence of development of antibiotic resistance.
      In a 6 month active comparator trial of 273 CF patients receiving either Cayston® or TIS, Cayston® was superior to TIS with regard to lung function improvements, with a treatment difference of 7.8% at 28 days and 2.7% at 24 weeks. Significant reductions in pulmonary exacerbations and mean change in CFQ-R RSS after 28 days of Cayston treatment were also seen, compared to TIS. In the follow-on 6 month open-label extension of this active comparator trial, the FEV1 response of previous TIS subjects who were switched to Cayston® improved and was sustained over time. Patients receiving Cayston® also gained weight throughout the 12 month trial, compared to those who received TIS who initially lost weight and then improved upon switch to Cayston® [

      Assael BM, Pressler T, Bilton D, Fayond M, Fischer R, Chiron R, et al. Inhaled aztreonam lysine vs. inhaled tobramycin in cystic fibrosis: A comparative efficacy trial. J Cyst Fibros in press, http://dx.doi.org/10.1016/j.jcf.2012.07.006.

      ]. Cayston® is available in the EU, Switzerland, USA and Canada. Cayston® is licensed for use in patients 6 years and older.

      5.2.1 Colistin

      The polymyxin derivative colistimethate sodium increases Gram-negative bacterial membrane permeability causing cell death. It has been used by inhalation for many years in CF patients for the treatment of chronic P. aeruginosa lung infection [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ]. Colobreathe® (Forest Laboratories) contains 1,662,500 IU of colistimethate sodium inhalation powder, for the management of chronic P. aeruginosa pulmonary infections in CF patients, aged 6 years and older [

      Schuster A, Haliburn C, Döring G, et al. Safety, efficacy and convenience of colistimethate sodium dry powder for inhalation (Colobreathe® DPI) in cystic fibrosis patients: a randomised study Thorax in press.

      ]. In a phase III open-label trial, Colobreathe® (125 mg twice daily) was not inferior to TIS, based on change in FEV1 % predicted after 24 weeks [

      Schuster A, Haliburn C, Döring G, et al. Safety, efficacy and convenience of colistimethate sodium dry powder for inhalation (Colobreathe® DPI) in cystic fibrosis patients: a randomised study Thorax in press.

      ]. Colobreathe® was safe and well tolerated in adult and pediatric subjects with CF [

      Schuster A, Haliburn C, Döring G, et al. Safety, efficacy and convenience of colistimethate sodium dry powder for inhalation (Colobreathe® DPI) in cystic fibrosis patients: a randomised study Thorax in press.

      ]. Colobreathe® may be available in some EU countries in 2012.

      5.3 Medications in development

      5.3.1 Liposomal amikacin

      Liposomes are biodegradable vesicles composed of single or multiple phospholipid layers, which may protect entrapped polycationic antibiotics, such as aminoglycosides, from inactivation by polyanionic components present in sputum, such as mucins or DNA. In airways, liposomes can also be taken up by macrophages. Based on this notion, liposomal amikacin for inhalation (Arikace®, INSMED) comprised of neutral charge liposomes has been developed to improve the penetration of the aminoglycoside antibiotic into mucus plugs and P. aeruginosa biofilms [
      • Meers P.
      • Neville M.
      • Malinin V.
      • Scotto A.W.
      • Sardaryan G.
      • Kurumunda R.
      • et al.
      Biofilm penetration, triggered release and in vivo activity of inhaled liposomal amikacin in chronic Pseudomonas aeruginosa lung infections.
      ]. Clinical studies with Arikace, delivered via the eFlow® nebulizer system, revealed a sustained release of amikacin in CF lungs [
      • Okusanya O.O.
      • Bhavnani S.M.
      • Hammel J.
      • Minic P.
      • Dupont L.J.
      • Forrest A.
      • et al.
      Pharmacokinetic and pharmacodynamic evaluation of liposomal amikacin for inhalation in cystic fibrosis patients with chronic pseudomonal infection.
      ]. The clinical pharmacokinetics and pharmacodynamics of Arikace have been evaluated in Phase Ib studies in 24 CF patients with chronic P. aeruginosa infection who received 500 mg of Arikace once daily for 14 days [
      • Okusanya O.O.
      • Bhavnani S.M.
      • Hammel J.
      • Minic P.
      • Dupont L.J.
      • Forrest A.
      • et al.
      Pharmacokinetic and pharmacodynamic evaluation of liposomal amikacin for inhalation in cystic fibrosis patients with chronic pseudomonal infection.
      ]. Randomized, placebo-controlled dose escalating phase II trials in CF patients with chronic P. aeruginosa infection showed a dose response and indicated that Arikace, delivered at a dose of 560 mg once daily for 28 consecutive days, followed by 28 days off drug, demonstrated superior clinical benefit compared to placebo as measured by significant and sustained improvement in lung function and reduction in P. aeruginosa density [
      • Clancy J.P.
      • Minic P.
      • Dupont L.
      • Goss C.H.
      • Quittner A.L.
      • Lymp J.F.
      • et al.
      Full analyses of data from two phase II blinded and placebo-controlled studies of nebulized liposomal amikacin for inhalation (Arikace™) in the treatment of cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection.
      ]. Also, patients receiving Arikace showed superior improvement in their respiratory symptoms as compared to those on placebo [
      • Clancy J.P.
      • Minic P.
      • Dupont L.
      • Goss C.H.
      • Quittner A.L.
      • Lymp J.F.
      • et al.
      Full analyses of data from two phase II blinded and placebo-controlled studies of nebulized liposomal amikacin for inhalation (Arikace™) in the treatment of cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection.
      ]. In addition, Arikace® was well-tolerated [
      • Clancy J.P.
      • Minic P.
      • Dupont L.
      • Goss C.H.
      • Quittner A.L.
      • Lymp J.F.
      • et al.
      Full analyses of data from two phase II blinded and placebo-controlled studies of nebulized liposomal amikacin for inhalation (Arikace™) in the treatment of cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection.
      ].

      5.3.2 Ciproinhale

      Ciprofloxacin dry powder inhaler (DPI) has been developed for the management of chronic P. aeruginosa infection in CF patients. Ciprofloxacin DPI uses the PulmoSphere® technology. Phase I studies with ciprofloxacin DPI in pediatric and adult CF patients showed that high concentrations in the lung were achieved with very low systemic exposure following single and multiple dose administration. A Phase II study of ciprofloxacin DPI, given at 2 dose levels (32.5 and 48.75 mg) twice a day for 28 days, showed significant decrease in P. aeruginosa density compared to placebo, but did not significantly improve the primary endpoint FEV1. There was also no significant change in other endpoints such as respiratory symptoms or exacerbations [
      • Dorkin H.
      • Criollo M.
      • Reimnitz P.
      • Alder J.
      • Hampel B.
      Randomized, double-blind, placebo-controlled, multicenter study to evaluate the safety and efficacy of inhaled ciprofloxacin compared with placebo in patients with cystic fibrosis.
      ].

      5.3.3 Levofloxacin

      A novel formulation of levofloxacin, levofloxacin inhalation solution (MP-376, Aeroquin) is being developed for the management of chronic P. aeruginosa infection in CF patients. As with inhaled ciprofloxacin, pharmacokinetic studies show high levels in sputum with low systemic exposure [
      • Geller D.E.
      • Flume P.A.
      • Staab D.
      • Fischer R.
      • Loutit J.S.
      • Conrad D.J.
      Levofloxacin inhalation solution (MP-376) in patients with cystic fibrosis with Pseudomonas aeruginosa.
      ]. In a phase II study [
      • Geller D.E.
      • Flume P.A.
      • Staab D.
      • Fischer R.
      • Loutit J.S.
      • Conrad D.J.
      Levofloxacin inhalation solution (MP-376) in patients with cystic fibrosis with Pseudomonas aeruginosa.
      ], 151 patients with CF were randomized to one of three doses of MP-376 (120 mg every day, 240 mg every day, and 240 mg twice a day) or placebo for 28 days. The primary efficacy endpoint was the change in sputum P. aeruginosa density. All doses of MP-376 reduced P. aeruginosa sputum density at day 28. A dose-dependent increase in FEV1 was observed between the 240 mg MP-376 twice-daily group and placebo. A significantly reduced need for other anti-P. aeruginosa antibiotics was observed in all MP-376 treatment groups compared with placebo. MP-376 was generally well tolerated relative to placebo.

      5.3.4 Fosfomycin/tobramycin

      A broad spectrum combination antibiotic, consisting of fosfomycin and tobramycin, is currently developed for the management of chronic bacterial infection in CF patients. A phase II study has been completed (NCT00794586) in which the safety and efficacy of 2 dose combinations of fosfomycin/tobramycin for inhalation (FTI), following a 28-day course of AZLI in CF patients and P. aeruginosa lung infection has been evaluated [
      • Trapnell B.C.
      • McColley S.A.
      • Kissner D.G.
      • Rolfe M.W.
      • Rosen J.M.
      • McKevitt M.
      • et al.
      Fosfomycin/tobramycin for inhalation in patients with cystic fibrosis with pseudomonas airway infection.
      ].

      5.3.5 What is the best strategy of chronic suppressive antibiotics for P. aeruginosa?

      It is reasonable when initiating therapy for chronic airways infection to implement a strategy as was used during drug development; that is, an approved inhaled antibiotic should be used in repeated cycles of 4 weeks of treatment, followed by 4 weeks off treatment. However, the original strategy of four-week on–off cycle of TIS [
      • Ramsey B.W.
      • Pepe M.S.
      • Quan J.M.
      • Otto K.L.
      • Montgomery A.B.
      • Williams-Warren J.
      • et al.
      Intermittent administration of inhaled tobramycin in patients with cystic fibrosis.
      ], chosen for decreasing the development of resistance during antibiotic therapy, has been challenged as to whether it is the optimum treatment strategy noting the observation of a decrease in lung function during the off cycle [
      • Ramsey B.W.
      • Pepe M.S.
      • Quan J.M.
      • Otto K.L.
      • Montgomery A.B.
      • Williams-Warren J.
      • et al.
      Intermittent administration of inhaled tobramycin in patients with cystic fibrosis.
      ]. The development of new antibiotic formulations has now given clinicians and patients greater opportunity to determine the best treatment approach. Potential strategies could employ continuous antibiotic rather than an intermittent approach, or to use a rotation of antibiotics rather than a single antibiotic. Thus, it is recommended that therapeutic options for inhaled antibiotic therapy in patients with chronic P. aeruginosa infection include an intermittent one month-on one month-off regime for inhaled aminoglycosides or continuous administration for inhaled colistin. In parallel with re-evaluation of all other aspects of care, a change of the inhalation antibiotic regimen should be considered in patients who frequently suffer from acute exacerbations or whose lung function deteriorates rapidly. Patients may remain on an intermittent one month-on one month-off regime but administering another inhaled antibiotic in the off month cycle or administering continuously inhaled antibiotic is also rationale and may benefit those patients with unstable disease. Current evidence from short-term studies suggests that inhaled antibiotics are safe and that the benefit outweighs the possible risk.
      Combining different antibiotics in a given CF patient for treating chronic P. aeruginosa lung infection may prove useful, based on in vitro observations [
      • Pamp S.J.
      • Gjermansen M.
      • Johansen H.K.
      • Tolker-Nielsen T.
      Tolerance to the antimicrobial peptide colistin in Pseudomonas aeruginosa biofilms is linked to metabolically active cells, and depends on the pmr and mexAB-oprM genes.
      ,
      • Herrmann G.
      • Yang L.
      • Wu H.
      • Song Z.
      • Wang H.
      • Høiby N.
      • et al.
      Colistin/tobramycin combinations are superior to monotherapy concerning the killing of biofilm P. aeruginosa.
      ] and animal experiments [
      • Herrmann G.
      • Yang L.
      • Wu H.
      • Song Z.
      • Wang H.
      • Høiby N.
      • et al.
      Colistin/tobramycin combinations are superior to monotherapy concerning the killing of biofilm P. aeruginosa.
      ].

      6. Optimizing antibiotic therapy for treatment of acute exacerbations of chronic P. aeruginosa infections

      During chronic bacterial lung infection, CF patients suffer from acute worsening of signs and symptoms, often called an acute pulmonary exacerbation [
      • Smyth A.
      • Elborn J.S.
      Exacerbations in cystic fibrosis: 3-Management.
      ], a phenomenon for which the pathophysiology has not been completely elucidated. Antibiotics are typically a component of the treatment of a pulmonary exacerbation. Besides maintaining lung function, a further important goal of antibiotic therapy for chronic P. aeruginosa infection is to prolong the time period to the next acute respiratory exacerbation [
      • Amadori A.
      • Atonellia A.
      • Balteria I.
      • Schreiber A.
      • Bugianib M.
      • De Rose V.
      Recurrent exacerbations affect FEV1 decline in adult patients with cystic fibrosis.
      ]. Some have recommended systemic antibiotics for the treatment of acute exacerbations [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ], based upon the rationale that an increased production of mucus plugs that obstruct the airways during acute exacerbations, may allow inhaled antibiotics only to reach the bacterial pathogens in the larger bronchi, but not in deeper areas of the respiratory tract. There is no evidence that using inhaled antibiotics during a course of intravenous antibiotics adds additional benefit. Even so, inhaled antibiotics were reportedly used in one fourth of pulmonary exacerbations in North America between the years 2003 and 2005 [
      • Moskowitz S.
      • Sliva S.
      • Mayer-Hamblett N.
      • Pasta D.J.
      • Mink D.R.
      • Mabie J.A.
      • et al.
      Shifting patterns of inhaled antibiotic use in cystic fibrosis.
      ].
      A significant decrease of P. aeruginosa cell numbers and an increase in lung function after a course of antibiotics should in theory be linked to a considerably large bacterial population in the patients' airways which is susceptible to the given antibiotic. Thus, reliable in vitro antibiotic susceptibility testing should establish this link [
      • Razvi S.
      • Saiman L.
      Microbiology of cystic fibrosis: role of the clinical microbiology laboratory, susceptibility and synergy studies and infection control.
      ]. However, substantial differences in antibiotic susceptibilities between P. aeruginosa isolates with the same colony morphology, and inconsistent results from different laboratories question this approach [
      • Foweraker J.E.
      • Laughton C.R.
      • Brown D.F.
      • Bilton D.
      Comparison of methods to test antibiotic combinations against heterogeneous populations of multiresistant Pseudomonas aeruginosa from patients with acute infective exacerbations in cystic fibrosis.
      ,
      • Ciofu O.
      • Fussing V.
      • Bagge N.
      • Koch C.
      • Høiby N.
      Characterization of paired mucoid/non-mucoid Pseudomonas aeruginosa isolates fom Danish cystic fibrosis patients: antibiotic resistance, beta-lactamase activity and riboprinting.
      ,
      • Foweraker J.E.
      • Laughton C.R.
      • Brown D.F.
      • Bilton D.
      Phenotypic variability of Pseudomonas aeruginosa in sputa from patients with acute infective exacerbation of cystic fibrosis and its impact on the validity of antimicrobial susceptibility testing.
      ]. A poor correlation between in vitro susceptibility data and clinical outcome in chronically infected CF patients after antibiotic therapy courses has been demonstrated [
      • Aaron S.D.
      • Vandemheen K.L.
      • Ferris W.
      • Fergusson D.
      • Tullis E.
      • Haase D.
      • et al.
      Combination antibiotic susceptibility testing to treat exacerbations of cystic fibrosis associated with multiresistant bacteria: a randomised, double-blind, controlled clinical trial.
      ,
      • Moskowitz S.M.
      • Emerson J.C.
      • McNamara S.
      • Shell R.D.
      • Orenstein D.M.
      • Rosenbluth D.
      • et al.
      Randomized trial of biofilm testing to select antibiotics for cystic fibrosis airway infection.
      ,
      • Smith A.L.
      • Fiel S.B.
      • Mayer-Hamblett N.
      • Ramsey B.
      • Burns J.L.
      Susceptibility testing of Pseudomonas aeruginosa isolates and clinical response to parenteral antibiotic administration: lack of association in cystic fibrosis.
      ]. Thus, not surprisingly, a critical assessment of the success rate of a given antibiotic treatment course using microbiological data is often missing and rather indirect clinical data are used to evaluate a given treatment option in this context [
      • Stenbit A.E.
      • Flume P.A.
      Pulmonary exacerbations in cystic fibrosis.
      ].
      One quarter of CF patients treated with antibiotics for acute exacerbations did not recover to baseline lung function [
      • Sanders D.B.
      • Bittner R.C.
      • Rosenfeld M.
      • Hoffman L.R.
      • Redding G.J.
      • Goss C.H.
      Failure to recover to baseline pulmonary function after cystic fibrosis pulmonary exacerbation.
      ,
      • Parkins M.D.
      • Rendall J.C.
      • Elborn J.S.
      Incidence and risk factors for pulmonary exacerbation treatment failures in cystic fibrosis patients chronically infected with Pseudomonas aeruginosa.
      ]. In one study, 57% of exacerbations were successfully treated even though the P. aeruginosa was resistant to the antibiotics used for treatment [
      • Parkins M.D.
      • Rendall J.C.
      • Elborn J.S.
      Incidence and risk factors for pulmonary exacerbation treatment failures in cystic fibrosis patients chronically infected with Pseudomonas aeruginosa.
      ]. This leads to the question, whether antibiotic therapy for patients with CF should be selected and rationalized on the basis of in vitro antibiotic susceptibility testing or whether routine susceptibility testing in P. aeruginosa should be abandoned as there is no relation between the outcome of treatment for exacerbations and the in vitro susceptibility for the systemic antibiotics used.
      What is the optimal antibiotic treatment of acute exacerbations of chronic P. aeruginosa infection? There is no evidence to support the use of inhaled antibiotics in addition to intravenously administered antibiotics. If an antibiotic is administered by two different routes of administration, potential additional toxicity should be considered. For instance in cases of significant renal impairment, inhaled aminoglycosides are frequently used for treatment of exacerbations limiting further systemic toxicity. There is no evidence to treat pulmonary exacerbations with inhaled antibiotics only.

      6.1 What is the optimal duration of antibiotic therapy for treatment of acute exacerbations of chronic P. aeruginosa infection?

      The length of antibiotic therapy for acute exacerbations in CF patients, typically 10–14 days [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ,
      • Smyth A.
      • Elborn J.S.
      Exacerbations in cystic fibrosis: 3-Management.
      ], is defined by clinical [
      • VanDevanter D.R.
      • O'Riordan M.A.
      • Blumer J.L.
      • Konstan M.W.
      Assessing time to pulmonary function benefit following antibiotic treatment of acute cystic fibrosis exacerbations.
      ] rather than by quantitative microbial data. The latter may shed some light on the question whether the established time frame for the treatment is justified or needs to be changed. Thus, it is recommended that exacerbations should be treated until symptoms resolve and lung function recovers, however therapy should not be extended more than 3weeks, except under very special circumstances. Patients with multi-drug resistant P. aeruginosa infection may require longer therapy. Careful evaluation of the patients' clinical status is required throughout the course of therapy.

      7. Current role of microbiological testing in the clinical care of patients as well as in clinical trials

      The understanding of the pathophysiology of CF airways disease has depended on the ability to identify pathogens through standard and novel microbiology methods. Optimal clinical care of the CF patient requires access to a sophisticated microbiology laboratory that is able to perform diagnostic testing relevant to CF disease. What is evolving is our understanding of how best to use the information derived from the microbiology lab to provide optimal care.
      As P. aeruginosa is known to be associated with worse lung disease and current treatment strategies have shown benefit to AET, it appears necessary to treat early infection with the hopes of eradicating the infection (Table 1). Early acquisition of P. aeruginosa may not cause symptoms, suggesting that routine surveillance cultures of respiratory specimens should be performed. Thus, what is the best method of routine surveillance for infection of the CF airways?
      Early diagnosis of P. aeruginosa lung infections may be difficult in patients not producing sputum [
      • Rosenfeld M.
      • Gibson R.L.
      • McNamara S.
      • Emerson J.
      • Burns J.L.
      • Castile R.
      • et al.
      Early pulmonary infection, inflammation, and clinical outcomes in infants with cystic fibrosis.
      ,
      • Burns J.L.
      • Gibson R.L.
      • McNamara S.
      • Yim D.
      • Emerson J.
      • Rosenfeld M.
      • et al.
      Longitudinal assessment of Pseudomonas aeruginosa in young children with cystic fibrosis.
      ]. Thus, nasopharyngeal aspirate, throat or cough swabs, sputum induction, bronchoalveolar lavage (BAL) and serological tests have been used for detecting infection with P. aeruginosa [
      • Döring G.
      • Hoiby N.
      • for the Consensus Study Group
      Early intervention and prevention of lung disease in cystic fibrosis: a European consensus.
      ]. Antibody testing against the P. aeruginosa enzymes AP, ELA and ExoA offers high sensitivity and specificity for the presence of P. aeruginosa in respiratory cultures of CF patients [
      • Ratjen F.
      • Walter H.
      • Haug M.
      • Meisner C.
      • Grasemann H.
      • Döring G.
      Diagnostic value of serum antibodies in early Pseudomonas aeruginosa infection in cystic fibrosis patients.
      ]. Also other assays have been developed [
      • Pressler T.
      • Karpati F.
      • Granström M.
      • Knudsen P.K.
      • Lindblad A.
      • Hjelte L.
      • et al.
      Diagnostic significance of measurements of specific IgG antibodies to Pseudomonas aeruginosa by three different serological methods.
      ]. Early identification of P. aeruginosa by BAL did not improve the outcome of early eradication compared to conventional techniques [
      • Wainwright C.E.
      • Vidmar S.
      • Armstrong D.S.
      • Byrnes C.A.
      • Carlin J.B.
      • Cheney J.
      • et al.
      Effect of bronchoalveolar lavage-directed therapy on Pseudomonas aeruginosa infection and structural lung injury in children with cystic fibrosis: a randomized trial.
      ]. P. aeruginosa serology has been demonstrated to be a useful marker for successful eradication of the pathogen [
      • Taccetti G.
      • Campana S.
      • Festini F.
      • Mascherini M.
      • Döring G.
      Early eradication therapy against Pseudomonas aeruginosa in cystic fibrosis patients.
      ,
      • Ratjen F.
      • Döring G.
      • Nikolaizik W.H.
      Effect of inhaled tobramycin on early Pseudomonas aeruginosa colonisation in patients with cystic fibrosis.
      ,
      • Ratjen F.
      • Walter H.
      • Haug M.
      • Meisner C.
      • Grasemann H.
      • Döring G.
      Diagnostic value of serum antibodies in early Pseudomonas aeruginosa infection in cystic fibrosis patients.
      ] and elevated levels of specific anti-P. aeruginosa antibodies have been shown to be a risk factor for developing chronic P. aeruginosa infection [
      • Pressler T.
      • Karpati F.
      • Granström M.
      • Knudsen P.K.
      • Lindblad A.
      • Hjelte L.
      • et al.
      Diagnostic significance of measurements of specific IgG antibodies to Pseudomonas aeruginosa by three different serological methods.
      ]. Thus, periodic monitoring of the patient who has never been infected or who has had successful eradication should be performed and a period of no more than 3months is acceptable. For those patients who have a new infection that is treated with AET, a subsequent culture should be obtained 24weeks after completion of the antibiotics to assess eradication. Routine serological testing is not recommended.
      For those patients with chronic infection, there is benefit to routine monitoring, especially for those who are on suppressive antibiotic therapy or who have had acute pulmonary exacerbations. Patients with chronic infection do aquire new infections so regular culture is potentially of benefit. The emergence of bacterial species in antibiotic treated patients has been investigated using culture-based methods in several clinical studies. For instance, in the ELITE trial [
      • Ratjen F.
      • Munck A.
      • Kho P.
      • Angyalosi G.
      ELITE Study Group. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial.
      ], regular monthly monitoring of respiratory cultures in the first year did not reveal obvious trends in the emergence of non-P. aeruginosa pathogens. However, clearly only a very small number of microbial species have been investigated on a qualitative basis.

      7.1 What is the role for antibiotic susceptibility testing?

      Susceptibility testing may not be helpful for selecting antibiotics for those patients with chronic infection as they have not proven to be predictive of outcomes. Antibiotic susceptibility may not apply to chronic inhalation therapy because a resistant organism according to conventional breakpoints may be still susceptible due to the high level of antibiotic applied. Susceptibility testing may not be helpful for selecting antibiotics for treatment of acute exacerbations as patients may respond clinically in spite of in vitro resistance. Furthermore, it remains unclear whether specific clinical information can be used to identify individuals at increased risk of initial management failure [
      • Sanders D.B.
      • Bittner R.C.
      • Rosenfeld M.
      • Hoffman L.R.
      • Redding G.J.
      • Goss C.H.
      Failure to recover to baseline pulmonary function after cystic fibrosis pulmonary exacerbation.
      ,
      • Parkins M.D.
      • Rendall J.C.
      • Elborn J.S.
      Incidence and risk factors for pulmonary exacerbation treatment failures in cystic fibrosis patients chronically infected with Pseudomonas aeruginosa.
      ]. P. aeruginosa susceptibility testing should be considered for (a) surveillance of resistant or multi-resistant P. aeruginosa strains in combination with strain typing; (b) when a new isolate of P. aeruginosa is identified in an individual patient; and (c) when a change of therapy (intravenous, nebulized or oral) is proposed because of a lack of response to treatment. The finding of in vitro antibiotic resistance does not necessarily indicate that treatment should be changed if the patient is responding to the current therapy.

      7.2 What is the role for quantification of bacteria?

      The correct determination of bacterial cell numbers including those for P. aeruginosa before and after a course of antibiotics is labor intensive, particularly when culture-based strategies are used. During chronic infection P. aeruginosa cell numbers may reach 107 to 108 colony forming units (cfu) per gram of sputum [
      • Regelmann W.E.
      • Elliott G.R.
      • Warwick W.J.
      • Clawson C.C.
      Reduction of sputum Pseudomonas aeruginosa density by antibiotics improves lung function in cystic fibrosis more than do bronchodilators and chest physiotherapy alone.
      ,
      • Tunney M.M.
      • Klem E.R.
      • Fodor A.A.
      • Gilpin D.F.
      • Moriarty T.F.
      • McGrath S.J.
      • et al.
      Use of culture and molecular analysis to determine the effect of antibiotic treatment on microbial community diversity and abundance during exacerbation in patients with cystic fibrosis.
      ] and a reduction of two log orders of magnitude after antibiotic therapy can be regarded as a major effect [
      • Regelmann W.E.
      • Elliott G.R.
      • Warwick W.J.
      • Clawson C.C.
      Reduction of sputum Pseudomonas aeruginosa density by antibiotics improves lung function in cystic fibrosis more than do bronchodilators and chest physiotherapy alone.
      ,
      • Meyer K.C.
      • Lewandoski J.R.
      • Zimmerman J.J.
      • Nunley D.
      • Calhoun W.J.
      • Dopico G.A.
      Human neutrophil elastase and elastase/alpha1-antiprotease complex in cystic fibrosis — comparison with interstitial lung disease and evaluation of the effect of intravenously administered antibiotic therapy.
      ].
      Quantitation of bacteria has been used to measure the microbiological effect of inhaled antibiotics and a reduction in bacterial numbers was seen in early studies of inhaled therapy [
      • Trapnell B.C.
      • McColley S.A.
      • Kissner D.G.
      • Rolfe M.W.
      • Rosen J.M.
      • McKevitt M.
      • et al.
      Fosfomycin/tobramycin for inhalation in patients with cystic fibrosis with pseudomonas airway infection.
      ]. There are conflicting reports of the impact of treatment for acute exacerbation on the bacterial load in the airways. Some studies show an average reduction in cfu following antibiotics for acute exacerbation [
      • Regelmann W.E.
      • Elliott G.R.
      • Warwick W.J.
      • Clawson C.C.
      Reduction of sputum Pseudomonas aeruginosa density by antibiotics improves lung function in cystic fibrosis more than do bronchodilators and chest physiotherapy alone.
      ] but others have shown a range of post treatment bacterial load indicating that bacterial numbers do not decrease in all patients [
      • Yang L.
      • Jelsbak L.
      • Marvig R.L.
      • Damkiæra S.
      • Workmana C.T.
      • Rau M.H.
      • et al.
      Evolutionary dynamics of bacteria in a human host environment.
      ,
      • Tunney M.M.
      • Field T.R.
      • Moriarty T.F.
      • Patrick S.
      • Doering G.
      • Muhlebach M.S.
      • et al.
      Detection of anaerobic bacteria in high numbers in sputum from patients with cystic fibrosis.
      ]. Sputum specimens may differ in viscosity and contain various bacterial phenotypes including small colony variants, which may be difficult to culture. This can make reliable bacterial quantitation difficult using conventional culture based methods. At this time, quantification of bacteria does not offer clinical utility but may still prove useful in clinical trials.

      7.3 What is the role for culture-independent microbiology?

      Culture-independent diagnostic methods such as quantitative polymerase chain reaction (qPCR) can determine total bacteria or bacteria belonging to a particular species in clinical samples and may avoid problems associated with culture-based strategies [
      • Tunney M.M.
      • Klem E.R.
      • Fodor A.A.
      • Gilpin D.F.
      • Moriarty T.F.
      • McGrath S.J.
      • et al.
      Use of culture and molecular analysis to determine the effect of antibiotic treatment on microbial community diversity and abundance during exacerbation in patients with cystic fibrosis.
      ,
      • Rogers G.B.
      • Marsh P.
      • Stressmann A.F.
      • Allen C.E.
      • Daniels T.V.W.
      • Carroll M.P.
      • et al.
      The exclusion of dead bacterial cells is essential for accurate molecular analysis of clinical samples.
      ,
      • Fodor A.A.
      • Klem E.R.
      • Gilpin D.F.
      • Elborn J.S.
      • Boucher R.C.
      • Tunney M.M.
      • et al.
      The adult cystic fibrosis airway microbiota is stable over time and infection type, and highly resilient to antibiotic treatment of exacerbations.
      ,
      • Blainey P.C.
      • Milla C.E.
      • Cornfield D.N.
      • Quake S.R.
      Quantitative analysis of the human airway microbial ecology reveals a pervasive signature for cystic fibrosis.
      ]. The inherent problem of qPCR relates to the inability of this approach to distinguish between living or dead bacterial cells. Such differentiation is needed to evaluate the impact of antibiotic therapy. This may be successfully circumvented by tagging bacterial DNA in viable cells with propidium monoazide photo-crosslinking before analysis or the use of RNA-based techniques [
      • Rogers G.B.
      • Marsh P.
      • Stressmann A.F.
      • Allen C.E.
      • Daniels T.V.W.
      • Carroll M.P.
      • et al.
      The exclusion of dead bacterial cells is essential for accurate molecular analysis of clinical samples.
      ]. This method could also shed light on the question whether a P. aeruginosa-specific antibiotic therapy would also affect cell numbers of other CF-related pathogens such as H. influenzae [
      • Smith A.L.
      • Doershuk C.
      • Goldmann D.
      • Gore E.
      • Hilman B.
      Comparison of a beta-lactam alone versus beta-lactam and an aminoglycoside for pulmonary exacerbation in cystic fibrosis.
      ] and S. aureus [
      • Bjarnsholt T.
      • Østrup Jensen P.
      • Jakobsen T.H.
      • Phipps R.
      • Nielsen A.K.
      • Rybtke M.T.
      • et al.
      Quorum sensing and virulence of Pseudomonas aeruginosa during lung infection of cystic fibrosis patients.
      ]. However, molecular methods have shown a large heterogeneity of bacterial species and their concentrations within a given sputum sample [
      • Rogers G.B.
      • Marsh P.
      • Stressmann A.F.
      • Allen C.E.
      • Daniels T.V.W.
      • Carroll M.P.
      • et al.
      The exclusion of dead bacterial cells is essential for accurate molecular analysis of clinical samples.
      ] and it is not known what role these other microorganisms play in the pathogenicity of lung infection in CF. Furthermore, the results of culture-independent diagnostic methods may vary with regard to the DNA isolation method used [
      • Rogers G.B.
      • Marsh P.
      • Stressmann A.F.
      • Allen C.E.
      • Daniels T.V.W.
      • Carroll M.P.
      • et al.
      The exclusion of dead bacterial cells is essential for accurate molecular analysis of clinical samples.
      ,
      • Zhao J.
      • Schloss P.D.
      • Kalikin L.M.
      • et al.
      Decade-long bacterial community dynamics in cystic fibrosis airway.
      ]. Finally, culture-independent techniques have not been validated and reproducibility is an important issue, it remains uncertain whether these quantitative culture-independent microbial diagnostic techniques should be used instead of culture-based methods to assess the efficacy of antibiotic therapies in CF patients or whether antibiotic therapy should be guided by clinical and lung function parameters alone.
      Culture-independent diagnostic methods for the detection of microbial species have also demonstrated that CF sputum specimens generally contain a larger number of different bacterial species in high concentrations than we thought previously [
      • Rogers G.B.
      • Hoffman L.R.
      • Döring G.
      Novel concepts in evaluating antimicrobial therapy for bacterial lung infections in patients with cystic fibrosis.
      ]. For instance, several strict anaerobic species may be present in CF sputum in numbers comparable to those of P. aeruginosa [
      • Tunney M.M.
      • Field T.R.
      • Moriarty T.F.
      • Patrick S.
      • Doering G.
      • Muhlebach M.S.
      • et al.
      Detection of anaerobic bacteria in high numbers in sputum from patients with cystic fibrosis.
      ]. This novel insight immediately raises the question whether specific antibiotic therapy against P. aeruginosa would not only affect P. aeruginosa alone but would also change the composition of the larger microbiota in the CF airways. Theoretically, a decrease of P. aeruginosa during effective antibiotic therapy may provoke the growth of other species already present in the microbiota which would dampen the beneficial effect of the antibiotic on inflammation, tissue destruction and lung function. On the other hand, it may cause a significant reduction of other antibiotic susceptible bacterial species leading to less inflammation and tissue destruction and increased lung function. At this time, culture-independent diagnostic methods do not offer clinical utility but may prove useful in clinical trials.

      8. Current status of antibiotic treatment of other bacterial pathogens

      As noted earlier, traditional and novel methods of microbiology have demonstrated that the airways infection in CF is rather complex, and include multiple bacterial species. The most common species include S. aureus, both methicillin-susceptible (MSSA) and methicillin-resistant (MRSA), H. influenzae, S. maltophilia, A. xylosoxidans, members of the Burkholderia cepacia complex, and non-tuberculous mycobacteria (NTM) species [
      • Fibrosis Trust Cystic
      Antibiotic Treatment for Cystic Fibrosis — Report of the UK Cystic Fibrosis Antibiotic Working Group.
      ]. It is likely that these microorganisms also contribute to lung inflammation and lung tissue destruction/remodeling. As evidence is growing that these are indeed pathogens in the CF airways, it would seem appropriate to consider using similar treatment strategies against them as are used to treat P. aeruginosa, including AET and chronic antibiotic suppression. Unfortunately there are no data to support the clinical benefit for either strategy for these organisms.

      8.1 S. aureus

      S. aureus has long been found in the airways of CF patients and has been thought to be a predecessor of later infection by P. aeruginosa and appears to be associated with increased lower airway inflammation [
      • Sagel S.D.
      • Gibson R.L.
      • Emerson J.
      • McNamara S.
      • Burns J.L.
      • Wagener J.S.
      • et al.
      Impact of Pseudomonas and staphylococcus infection on inflammation and clinical status in young children with cystic fibrosis.
      ,
      • Gangell C.
      • Gard S.
      • Douglas T.
      • Park J.
      • de Klerk N.
      • Keil T.
      • et al.
      Inflammatory responses to individual microorganisms in the lungs of children with cystic fibrosis.
      ]. As such, some have advocated for prophylactic therapy against S. aureus [
      • Smyth A.
      • Walters S.
      ], a strategy that is being recommended in the UK and other countries [
      • Fibrosis Trust Cystic
      Antibiotic Treatment for Cystic Fibrosis — Report of the UK Cystic Fibrosis Antibiotic Working Group.
      ] but has not been adopted by clinical practice guidelines in the US [
      • Flume P.A.
      • O'Sullivan B.P.
      • Robinson K.A.
      • Goss C.H.
      • Mogayzel Jr, P.J.
      • Willey-Courand D.B.
      • et al.
      Cystic fibrosis pulmonary guidelines. Chronic medications for maintenance of lung health.
      ]. This is based upon data from a long-term placebo controlled trial in which there was no clinical benefit for those on prophylactic antibiotic therapy after 7 years of treatment [
      • Stutman H.R.
      • Lieberman J.M.
      • Nussbaum E.
      • Marks M.I.
      Antibiotic prophylaxis in infants and young children with cystic fibrosis: a randomized controlled trial.
      ].
      MRSA strains have been increasingly recognized among CF patients in the last decade [
      Cystic fibrosis foundation patient registry 2009 annual data report.
      ,
      • Miall L.S.
      • McGinley N.T.
      • Brownlee K.G.
      • Conway S.P.
      Methicillin resistant Staphylococcus aureus (MRSA) infection in cystic fibrosis.
      ]. In a recent epidemiological study in Italy Penton Valentine Leukocidin (PVL)-negative MRSA strains with a high resistance rate to clindamycin and moderate resistance to trimethoprim/sulpha-methoxazole were detected in 31.4% of Italian CF patients. Recent data suggest that MRSA strains are markers of more severe disease in CF patients but are not more virulent than MSSA strains [
      • Burns J.L.
      • Gibson R.L.
      • McNamara S.
      • Yim D.
      • Emerson J.
      • Rosenfeld M.
      • et al.
      Longitudinal assessment of Pseudomonas aeruginosa in young children with cystic fibrosis.
      ,
      • Wiesemann H.G.
      • Steinkamp G.
      • Ratjen F.
      • Bauernfeind A.
      • Przyklenk B.
      • Döring G.
      • et al.
      Placebo-controlled, double-blind, randomized study of aerolized tobramycin for early treatment of Pseudomonas aeruginosa infection in cystic fibrosis.
      ,
      • Gibson R.L.
      • Emerson J.
      • McNamara S.
      • Burns J.L.
      • Rosenfeld M.
      • Yunker A.
      • et al.
      Significant microbiological effect of inhaled tobramycin in young children with cystic fibrosis.
      ,
      • Van Ewijk B.E.
      • Wolfs T.F.W.
      • Fleer A.
      • Kimpen J.L.L.
      • Van der Ent C.K.
      High Pseudomonas aeruginosa acquisition rate during acute respiratory infection in healthy and cystic fibrosis children.
      ,
      • Lee T.W.R.
      • Brownlee K.G.
      • Conway S.P.
      • Denton M.
      • Littlewood J.M.
      Evaluation of a new definition for chronic Pseudomonas aeruginosa infection in cystic fibrosis patients.
      ,
      • Proesmans M.
      • Balinska-Miskiewicz W.
      • Dupont L.
      • Bossuyt X.
      • Verhaegen J.
      • Høiby N.
      • et al.
      Evaluating the “Leeds criteria” for Pseudomonas aeruginosa infection in a cystic fibrosis centre.
      ,
      • Taccetti G.
      • Campana S.
      • Festini F.
      • Mascherini M.
      • Döring G.
      Early eradication therapy against Pseudomonas aeruginosa in cystic fibrosis patients.
      ,
      • Kozlowska W.J.
      • Bush A.
      • Wade A.
      • Aurora P.
      • Carr S.B.
      • Castle R.A.
      • et al.
      Lung function from infancy to the preschool years after clinical diagnosis of cystic fibrosis.
      ,
      • Ratjen F.
      • Munck A.
      • Kho P.
      • Angyalosi G.
      ELITE Study Group. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial.
      ,
      • Treggiari M.M.
      • Retsch-Bogart G.
      • Mayer-Hamblett N.
      • Khan U.
      • Kulich M.
      • Kronmal R.
      • et al.
      Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis.
      ,
      • Amin R.
      • Lam M.
      • Dupuis A.
      • Ratjen F.
      The effect of early Pseudomonas aeruginosa treatment on lung function in pediatric cystic fibrosis.
      ,
      • Mayer-Hamblett N.
      • Kronmal R.A.
      • Gibson R.L.
      • Rosenfeld M.
      • Retsch-Bogart G.
      • Treggiari M.M.
      • et al.
      Initial Pseudomonas aeruginosa treatment failure is associated with exacerbations in cystic fibrosis.
      ,
      • Tramper-Stranders G.A.
      • van der Ent C.K.
      • Molin S.
      • Yang L.
      • Hansen S.K.
      • Rau M.H.
      • et al.
      Initial Pseudomonas aeruginosa infection in patients with cystic fibrosis: characteristics of eradicated and persistent isolates.
      ,
      • Döring G.
      • Meisner C.
      • Stern M.
      for the Flagella Vaccine Trial Study Group
      A double-blind randomized placebo-controlled phase III study of a Pseudomonas aeruginosa flagella vaccine in cystic fibrosis patients.
      ,
      • Cantón R.
      • Cobos N.
      • De Gracia J.
      • Baquero F.
      • Honorato J.
      • Gartner S.
      Antimicrobial therapy of pulmonary pathogenic colonisation and infection by Pseudomonas aeruginosa in cystic fibrosis patients.
      ,
      • Valerius N.H.
      • Koch C.
      • Høiby N.
      Prevention of chronic Pseudomonas aeruginosa colonisation in cystic fibrosis by early treatment.
      ,
      • Ratjen F.
      • Döring G.
      • Nikolaizik W.H.
      Effect of inhaled tobramycin on early Pseudomonas aeruginosa colonisation in patients with cystic fibrosis.
      ,
      • Gibson R.L.
      • Emerson J.
      • Mayer-Hamblett N.
      • Burns J.L.
      • McNamara S.
      • Accurso F.J.
      • et al.
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      An 18-month study of the safety and efficacy of repeated courses of inhaled aztreonam lysine in cystic fibrosis.
      ,
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      Effect of bronchoalveolar lavage-directed therapy on Pseudomonas aeruginosa infection and structural lung injury in children with cystic fibrosis: a randomized trial.
      ,

      Assael BM, Pressler T, Bilton D, Fayond M, Fischer R, Chiron R, et al. Inhaled aztreonam lysine vs. inhaled tobramycin in cystic fibrosis: A comparative efficacy trial. J Cyst Fibros in press, http://dx.doi.org/10.1016/j.jcf.2012.07.006.

      ,

      Schuster A, Haliburn C, Döring G, et al. Safety, efficacy and convenience of colistimethate sodium dry powder for inhalation (Colobreathe® DPI) in cystic fibrosis patients: a randomised study Thorax in press.

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      Biofilm penetration, triggered release and in vivo activity of inhaled liposomal amikacin in chronic Pseudomonas aeruginosa lung infections.
      ,
      • Okusanya O.O.
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      Pharmacokinetic and pharmacodynamic evaluation of liposomal amikacin for inhalation in cystic fibrosis patients with chronic pseudomonal infection.
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      • Clancy J.P.
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      ,
      • Dorkin H.
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      Randomized, double-blind, placebo-controlled, multicenter study to evaluate the safety and efficacy of inhaled ciprofloxacin compared with placebo in patients with cystic fibrosis.
      ,
      • Geller D.E.
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      • Fischer R.
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      Levofloxacin inhalation solution (MP-376) in patients with cystic fibrosis with Pseudomonas aeruginosa.
      ,
      • Trapnell B.C.
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      Fosfomycin/tobramycin for inhalation in patients with cystic fibrosis with pseudomonas airway infection.
      ,
      • Ramsey B.W.
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      Intermittent administration of inhaled tobramycin in patients with cystic fibrosis.
      ,
      • Pamp S.J.
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      Tolerance to the antimicrobial peptide colistin in Pseudomonas aeruginosa biofilms is linked to metabolically active cells, and depends on the pmr and mexAB-oprM genes.
      ,
      • Herrmann G.
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      Colistin/tobramycin combinations are superior to monotherapy concerning the killing of biofilm P. aeruginosa.
      ,
      • Smyth A.
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      Exacerbations in cystic fibrosis: 3-Management.
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      • Amadori A.
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      Recurrent exacerbations affect FEV1 decline in adult patients with cystic fibrosis.
      ,
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      ,
      • Ciofu O.
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      Characterization of paired mucoid/non-mucoid Pseudomonas aeruginosa isolates fom Danish cystic fibrosis patients: antibiotic resistance, beta-lactamase activity and riboprinting.
      ,
      • Foweraker J.E.
      • Laughton C.R.
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      • Bilton D.
      Phenotypic variability of Pseudomonas aeruginosa in sputa from patients with acute infective exacerbation of cystic fibrosis and its impact on the validity of antimicrobial susceptibility testing.
      ,
      • Aaron S.D.
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      Combination antibiotic susceptibility testing to treat exacerbations of cystic fibrosis associated with multiresistant bacteria: a randomised, double-blind, controlled clinical trial.
      ,
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      Randomized trial of biofilm testing to select antibiotics for cystic fibrosis airway infection.
      ,
      • Smith A.L.
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      Susceptibility testing of Pseudomonas aeruginosa isolates and clinical response to parenteral antibiotic administration: lack of association in cystic fibrosis.
      ,
      • Stenbit A.E.
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      Pulmonary exacerbations in cystic fibrosis.
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      • Sanders D.B.
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      Failure to recover to baseline pulmonary function after cystic fibrosis pulmonary exacerbation.
      ,
      • Parkins M.D.
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      • Elborn J.S.
      Incidence and risk factors for pulmonary exacerbation treatment failures in cystic fibrosis patients chronically infected with Pseudomonas aeruginosa.
      ,
      • VanDevanter D.R.
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      • Blumer J.L.
      • Konstan M.W.
      Assessing time to pulmonary function benefit following antibiotic treatment of acute cystic fibrosis exacerbations.
      ,
      • Ratjen F.
      • Walter H.
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      • Döring G.
      Diagnostic value of serum antibodies in early Pseudomonas aeruginosa infection in cystic fibrosis patients.
      ,
      • Pressler T.
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      • et al.
      Diagnostic significance of measurements of specific IgG antibodies to Pseudomonas aeruginosa by three different serological methods.
      ,
      • Regelmann W.E.
      • Elliott G.R.
      • Warwick W.J.
      • Clawson C.C.
      Reduction of sputum Pseudomonas aeruginosa density by antibiotics improves lung function in cystic fibrosis more than do bronchodilators and chest physiotherapy alone.
      ,
      • Tunney M.M.
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      Use of culture and molecular analysis to determine the effect of antibiotic treatment on microbial community diversity and abundance during exacerbation in patients with cystic fibrosis.
      ,
      • Meyer K.C.
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      • Nunley D.
      • Calhoun W.J.
      • Dopico G.A.
      Human neutrophil elastase and elastase/alpha1-antiprotease complex in cystic fibrosis — comparison with interstitial lung disease and evaluation of the effect of intravenously administered antibiotic therapy.
      ,
      • Tunney M.M.
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      Detection of anaerobic bacteria in high numbers in sputum from patients with cystic fibrosis.
      ,
      • Rogers G.B.
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      The exclusion of dead bacterial cells is essential for accurate molecular analysis of clinical samples.
      ,
      • Fodor A.A.
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      The adult cystic fibrosis airway microbiota is stable over time and infection type, and highly resilient to antibiotic treatment of exacerbations.
      ,
      • Blainey P.C.
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      • Cornfield D.N.
      • Quake S.R.
      Quantitative analysis of the human airway microbial ecology reveals a pervasive signature for cystic fibrosis.
      ,
      • Smith A.L.
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      • Hilman B.
      Comparison of a beta-lactam alone versus beta-lactam and an aminoglycoside for pulmonary exacerbation in cystic fibrosis.
      ,
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      ,
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      Impact of Pseudomonas and staphylococcus infection on inflammation and clinical status in young children with cystic fibrosis.
      ,
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      ,
      • Miall L.S.
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      • Brownlee K.G.
      • Conway S.P.
      Methicillin resistant Staphylococcus aureus (MRSA) infection in cystic fibrosis.
      ,
      • Dasenbrook E.C.
      • Merlo C.A.
      • Diener-West M.
      • Lechtzin N.
      • Boyle M.P.
      Persistent methicillin-resistant Staphylococcus aureus and rate of FEV1 decline in cystic fibrosis.
      ,
      • Sawicki G.S.
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      • Pasta D.J.
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      The impact of incident methicillin resistant Staphylococcus aureus detection on pulmonary function in cystic fibrosis. For the investigators and coordinators of the epidemiologic study of cystic fibrosis.
      ,
      • Dasenbrook E.C.
      • Checkley W.
      • Merlo C.A.
      • Konstan M.W.
      • Lechtzin N.
      • Boyle M.P.
      Association between respiratory tract methicillin-resistant Staphylococcus aureus and survival in cystic fibrosis.
      ,
      • Muhlebach M.S.
      • Miller M.
      • Lavange L.M.
      • Mayhew G.
      • Goodrich J.S.
      • Miller M.B.
      Treatment intensity and characteristics of MRSA infection in CF.
      ,
      • Goss C.H.
      • Muhlebach M.S.
      Staphylococcus aureus and MRSA in cystic fibrosis.
      ,
      • Vanderhelst E.
      • De Meirleir L.
      • Verbanck S.
      • Pierard D.
      • Vincken W.
      • Malfroot A.
      Prevalence and impact on FEV1 decline of chronic methicillin-resistant Staphylococcus aureus (MRSA) infection in patients with cystic fibrosis. A single-center, case–control study of 165 patients.
      ]. Acquisition of MRSA has been associated with hospitalization, the F508del genotype and the presence of bronchiectasis [
      • Vanderhelst E.
      • De Meirleir L.
      • Verbanck S.
      • Pierard D.
      • Vincken W.
      • Malfroot A.
      Prevalence and impact on FEV1 decline of chronic methicillin-resistant Staphylococcus aureus (MRSA) infection in patients with cystic fibrosis. A single-center, case–control study of 165 patients.
      ]. For treatment of S. aureus, recommended drugs, doses and regimens are given in Table 2.
      Other methods of infection control would also seem prudent. In countries with a policy of segregation and eradication of first infection of MRSA, chronic infection with MRSA is rare []. It seems that the rates of MRSA in CF patients parallel those in the overall community, suggesting that differing rates in different countries do not reflect different treatment modalities in the CF patient population.
      Table 2Recommended antibiotics for therapy against Staphylococcus aureus in patients with CF.
      AntibioticRoute of administrationDose (mg/kg/day)Administrations per dayMaximum daily dose

      (g)
      OralIV
      FlucloxacillinOral1003–44.512.0
      DicloxacillinOral, i.v.503–44.012.0
      Fusidic acidOral, i.v.25–502–32.02.0
      ClindamycinOral, i.v.20–402–41.81.8
      RifampicinOral, i.v.15–2020.60.6
      VancomycinI.v.4022.0
      TeicoplaninI.v.1010.8
      LinezolidOral, i.v. (<5 years)3031.21.2
      LinezolidOral, i.v. (>5 years)2021.21.2
      Cotrimoxazole (trimetoprim compound)Oral8–1020.32
      Amoxicillin/clavulanic acidOral50–10034.0
      Cefuroxime/axetilOral20–3021.0
      If rifampicin or fusidic acid or clindamycin or macrolides such as azithromycin are used, a high risk to develop resistance is present. Therefore these drugs should be considered in combination with e.g., dicloxacillin or flucloxacillin. For pathogens difficult to treat such as MRSA, rifampicin+fusidic acid or rifampicin+clindamycin can be used. Linezolid is an expensive drug and clinical experience is limited. Linezolid has a high barrier to the development of resistance. Long-term therapy with linezolid is associated with neuropathy. Other drugs listed should be used for combination therapy of MRSA. Augmentin (amoxicillin+clavulanic acid) is a broad-spectrum antibiotic and therefore influences the normal flora. It can be used when both H. influenzae and S. aureus are cultured
      • Dalbøge C.
      • Pressler T.
      • Høiby N.
      • Nielsen K.
      • Johansen H.K.
      A cohort study of the Copenhagen CF centre eradication strategy against Staphylococcus aureus in patients with CF.
      . Drug doses may need to be adapted according to comorbidities. Always check for drug–drug interactions, especially with fusidic acid and rifampicin.

      8.2 S. maltophilia and A. xylosoxidans

      S. maltophilia prevalence rates still vary considerably between CF centers with a mean prevalence rate of up to 25% in single centers [
      • Talmaciu I.
      • Varlotta L.
      • Mortensen J.
      • Schidlow D.V.
      Risk factors for emergence of Stenotrophomonas maltophilia in cystic fibrosis.
      ] with rapidly increasing prevalence in others [
      • De Vrankrijker A.M.M.
      • Wolfs T.F.W.
      • Van der Ent C.K.
      Challenging and emerging pathogens in cystic fibrosis.
      ]. Studies have presented conflicting data regarding the clinical significance of S. maltophilia [
      • Karpati F.
      • Malmborg A.-S.
      • Alfredsson H.
      • Hjelte L.
      • Strandvik B.
      Bacterial colonisation with Xanthomonas maltophilia — A retrospective study in a cystic fibrosis patient population.
      ,
      • Goss C.H.
      • Otto K.
      • Aitken M.L.
      • Rubenfeld G.D.
      Detecting Stenotrophomonas maltophilia does not reduce survival of patients with cystic fibrosis.
      ]. Chronic infection associated with the development of an immune response against the organism, predicts more exacerbations [
      • Waters V.
      • Yau Y.
      • Prasad S.
      • Lu A.
      • Atenafu E.
      • Crandall I.
      • et al.
      Stenotrophomonas maltophilia in cystic fibrosis: serologic response and effect on lung disease.
      ], but not more progression in decline of lung function [
      • Waters V.
      • Yau Y.
      • Prasad S.
      • Lu A.
      • Atenafu E.
      • Crandall I.
      • et al.
      Stenotrophomonas maltophilia in cystic fibrosis: serologic response and effect on lung disease.
      ]. Relatively little is known about the clinical significance of A xylosoxidans in CF and more studies are needed to determine when treatment should be given and which antibiotics should be used. Recommended antibiotics for therapy against S. maltophilia and A. xylosoxidans infections in patients with CF are given in Table 3.
      Table 3Recommended antibiotics for therapy against S. maltophilia and A. xyloxidans in patients with CF
      These species are resistant to many antibiotics and easily become resistant to antibiotics during treatment. Susceptibility testing must therefore guide the choice of antibiotics and combination therapy is usually recommended: Aztreonam/ticarcillin/clavulanic acid combination therapy because of synergism against S. maltophilia. Tetracyclines should not be used in children. Tobramycin drug levels need to be measured. Drug doses may need to be adapted according to comorbidities. Always check for drug–drug interactions.
      .
      AntibioticRoute of

      administration
      Dose

      (mg/kg/day)
      Administrations

      per day
      Maximum daily dose

      (g)
      OralIV
      MinocyclinOral2–31–20.2
      DoxycyclinOral2–310.2
      Sulfamethoxazol/trimetoprimOral, i.v.50–100+10–202–40.480.48
      CeftazidimeI.v.150–200312.0
      MeropenemI.v.100–15036
      Colistin **I.v.2–52–40.48
      TobramycinI.v.5–101–30.48
      CiprofloxacinOral, i.v.20–302–31.51.2
      AztreonamI.v.150–25038.0
      Ticarcillin/clavulanic acidI.v.200–300/6–104–616.0 (ticar comp)
      Piperacillin/tazobactamI.v.200–240/25–303–416.0 (piperacillin

      comp)
      low asterisk These species are resistant to many antibiotics and easily become resistant to antibiotics during treatment. Susceptibility testing must therefore guide the choice of antibiotics and combination therapy is usually recommended: Aztreonam/ticarcillin/clavulanic acid combination therapy because of synergism against S. maltophilia. Tetracyclines should not be used in children. Tobramycin drug levels need to be measured. Drug doses may need to be adapted according to comorbidities. Always check for drug–drug interactions.

      8.3 Burkholderia cepacia complex strains

      Other antibiotic resistant bacterial pathogens, associated with CF patients, include the Burkholderia cepacia complex (Bcc), a group of at least 17 closely related bacterial species [
      • LiPuma J.
      The changing microbial epidemiology in CF.
      ], from which B. cenocepacia, B. multivorans and B. dolosa are the most prevalent in CF. Due to its high virulence, effective antibiotics to treat Bcc-infected CF patients are urgently needed [
      • Nørskov-Lauritsen N.
      • Johansen H.K.
      • Fenger M.G.
      • Nielsen X.C.
      • Pressler T.
      • Olesen H.V.
      • et al.
      Unusual distribution of Burkholderia cepacia complex species in Danish cystic fibrosis clinics may stem from restricted transmission between patients.
      ]. Few trials have systematically examined the antibiotic treatment of Bcc infection in CF patients.
      Recently, a large randomized, controlled trial enrolled 101 CF patients to evaluate the safety and efficacy of Cayston® versus placebo in BCC-infected CF patients. Subjects received Cayston® or placebo continuously every month in addition to standard therapy for the first 6 months of the study. No difference in FEV1 was demonstrated between the two groups. No benefit was realized in the 6 month cross over phase [
      • Tullis E.
      • Burns J.
      • Retsch-Bogart G.
      • Bresnik M.
      • Henig N.
      • Lewis S.
      • et al.
      Aztreonam for inhalation solution (AZLI) in cystic fibrosis (CF) patients with chronic Burkholderia species (BURK) infection: final results from a randomized, placebo-controlled trial.
      ]. Recommended antibiotics for therapy against Bcc infections in patients with CF are given in Table 4.
      Table 4Recommended antibiotics for therapy against B. cepacia complex in patients with CF
      These species are resistant to many antibiotics and easily become resistant to antibiotics during treatment. Susceptibility testing must therefore guide the choice of antibiotics and combination therapy is usually recommended. For B. cepacia complex three i.v. drugs are recommended.
      .
      AntibioticRoute of

      administration
      Dose

      (mg/kg/day)
      Administrations

      per day
      Maximum daily dose

      (g)
      OralIV
      DoxycyclinOral2–310.20
      Sulfamethoxal/trimetoprimOral, i.v.50–100+10–202–40.48
      Trimethoprim compound.
      0.48
      Trimethoprim compound.
      CeftazidimeI.v.150–200312.0
      MeropenemI.v.12036.0
      TobramycinI.v.5–101–30.48
      AztreonamI.v.150–25038.0
      Ticarcillin/clavulanic acidI.v.200–300/6–104–616.0
      Ticarcillin and piperacillin compound. Drug doses may need to be adapted according to comorbidities. Always check for drug–drug interactions.
      Piperacillin/tazobactamI.v.200–240/25–303–416.0
      Ticarcillin and piperacillin compound. Drug doses may need to be adapted according to comorbidities. Always check for drug–drug interactions.
      low asterisk These species are resistant to many antibiotics and easily become resistant to antibiotics during treatment. Susceptibility testing must therefore guide the choice of antibiotics and combination therapy is usually recommended. For B. cepacia complex three i.v. drugs are recommended.
      low asterisklow asterisk Trimethoprim compound.
      low asterisklow asterisklow asterisk Ticarcillin and piperacillin compound. Drug doses may need to be adapted according to comorbidities. Always check for drug–drug interactions.

      8.4 NTM species

      Increasingly NTM species, in particular M. avium-intracellulare complex, M. chelonae and M. abscessus complex are diagnosed in airway specimens of mainly older CF patients [
      • Olivier K.N.
      • Weber D.J.
      • Lee J.H.
      • Handler A.
      • Tudor G.
      • Molina P.L.
      • et al.
      Nontuberculous mycobacteria.
      ]. Because infection is associated with an accelerated clinical decline [
      • Olivier K.N.
      • Weber D.J.
      • Lee J.H.
      • Handler A.
      • Tudor G.
      • Molina P.L.
      • et al.
      Nontuberculous mycobacteria.
      ], and clinical improvements have been observed after anti-mycobacterial therapy, these pathogens should be treated when associated with a clinical deterioration or when the patient does not respond to the antibiotic treatment against other microorganisms detected in parallel in respiratory cultures [
      • Fauroux B.
      • Delaisi B.
      • Clement A.
      • Saizou C.
      • Moissenet D.
      • Truffot-Pernot C.
      • et al.
      Mycobacterial lung disease in cystic fibrosis: a prospective study.
      ]. However, there is no treatment regimen that has been demonstrated to be routinely successful in deriving a clinical benefit or eradicating the infection.

      8.5 What is the optimal treatment strategy of NTM infections in CF patients?

      Diagnosis and treatment guidelines have been published [ATS guidelines] for NTM infections in general, and for CF in particular. Treatment of NTM infection is a serious commitment, requiring multiple antibiotics and for an extended treatment period [
      • Griffith D.E.
      • Aksamit T.
      • Brown-Elliott B.A.
      • Catanzaro A.
      • Daley C.
      • Gordin F.
      • et al.
      An official ATS/IDSA statement: diagnosis, treatment, and prevention of nontuberculous mycobacterial diseases.
      ] (Table 5, Table 6). Novel therapies are being considered. For example, the possibility that liposomes can be taken up by macrophages may provide Arikace® with enhanced activity against intracellular NTM species such as M. avium-intracellulare complex, M. chelonae and M. abscessus which are found in airway specimens of CF patients [
      • Olivier K.N.
      • Weber D.J.
      • Lee J.H.
      • Handler A.
      • Tudor G.
      • Molina P.L.
      • et al.
      Nontuberculous mycobacteria.
      ,
      • Esther C.R.
      • Henry M.M.
      • Molina P.L.
      • Leigh M.W.
      Nontuberculous mycobacterial infection in young children with cystic fibrosis.
      ].
      Table 5Recommended antibiotics for therapy against Mycobacterium avium complex infections in patients with CF.
      AntibioticRoute of

      administration
      Dose
      ClarithromycinOral500–1000mg/d
      AzithromycinOral250–300mg/d
      EthambutolOral15mg/kg/d
      RifabutinOral150–300mg/d
      RifampicinOral450–600mg/d
      AmikacinI.v.15mg/kg/day
      Aim for eradication: 12 months of negative sputum cultures while on therapy.
      Table 6Recommended antibiotics for therapy against Mycobacterium abscessus infections in patients with CF.
      AntibioticRoute of administrationDose
      ClarithromycinOral500–1000mg/d
      AzithromycinOral250–300mg/d
      Cefoxitin: i.v.200mg/kg/d
      Divided every 8h, max 12g.
      AmikacinI.v.15mg/kg/d
      Inhaled 250–500mg twice daily.
      Inhaled250–500mg twice daily
      Meropenem:I.v.40mg/kg
      Divided every 8h, max 6g.
      Tigecycline:I.v.50mg twice daily
      t1/2=40h. In case of hepatotoxicity 100mg every other day. Comment: aim for stable disease although reported cases show a decline in lung function despite maintenance therapy.
      LinezolidOral600mg twice daily
      Interferon gammas.c.25–50μg/m2, 2 or 3 times

      weekly
      low asterisk Divided every 8 h, max 12 g.
      low asterisklow asterisk Inhaled 250–500 mg twice daily.
      low asterisklow asterisklow asterisk Divided every 8 h, max 6 g.
      low asterisklow asterisklow asterisklow asterisk t1/2=40 h. In case of hepatotoxicity 100 mg every other day. Comment: aim for stable disease although reported cases show a decline in lung function despite maintenance therapy.
      Of note, the long-term use of the macrolide azithromycin has become an accepted therapy for patients with CF [
      • Flume P.A.
      • O'Sullivan B.P.
      • Robinson K.A.
      • Goss C.H.
      • Mogayzel Jr, P.J.
      • Willey-Courand D.B.
      • et al.
      Cystic fibrosis pulmonary guidelines. Chronic medications for maintenance of lung health.
      ]. Azithromycin has multiple beneficial effects on inflammation and lung physiology [
      • Rogers G.B.
      • Hoffman L.R.
      • Döring G.
      Novel concepts in evaluating antimicrobial therapy for bacterial lung infections in patients with cystic fibrosis.
      ,
      • Feldman C.
      • Anderson R.
      • Theron A.
      • Mokgobu I.
      • Cole P.J.
      • Wilson R.
      The effects of ketolides on bioactive phospholipid-induced injury to human respiratory epithelium in vitro.
      ,
      • Yousef A.A.
      • Jaffe A.
      The role of azithromycin in patients with cystic fibrosis.
      ,
      • Saiman L.
      • Anstead M.
      • Mayer-Hamblett N.
      • Lands L.C.
      • Kloster M.
      • Hocevar-Trnka J.
      • et al.
      Effect of azithromycin on pulmonary function in patients with cystic fibrosis uninfected with Pseudomonas aeruginosa: a randomized controlled trial.
      ] and reduces P. aeruginosa biofilm formation and quorum sensing regulated extracellular virulence factors [
      • Tateda K.
      • Comte R.
      • Pechere J.C.
      • Kohler T.
      • Yamaguchi K.
      • Van Delden C.
      Azithromycin inhibits quorum sensing in Pseudomonas aeruginosa.
      ,
      • Pérez-Martínez I.
      • Haas D.
      Azithromycin inhibits expression of the GacA-dependent small RNAs RsmY and RsmZ in Pseudomonas aeruginosa.
      ]. It is recommended that chronic macrolides are withheld in patients with NTM infection in order to prevent selection of resistant pathogens [
      • Flume P.A.
      • O'Sullivan B.P.
      • Robinson K.A.
      • Goss C.H.
      • Mogayzel Jr, P.J.
      • Willey-Courand D.B.
      • et al.
      Cystic fibrosis pulmonary guidelines. Chronic medications for maintenance of lung health.
      ]. Recent concern that macrolides may increase the risk of acquiring NTM infections is based upon in vitro studies of human macrophages where azithromycin prevented lysosomal acidification, thereby impairing autophagic and phagosomal degradation and as a consequence inhibited intracellular killing of mycobacteria within macrophages, resulting in chronic infection with NTM in mice [
      • Renna M.
      • Schaffner C.
      • Brown K.
      • Shang S.
      • Henao Tamayo M.
      • Hegyi K.
      • et al.
      Azithromycin blocks autophagy and may predispose cystic fibrosis patients to mycobacterial infection.
      ]. However, this phenomenon has not been observed in clinical CF trials with azithromycin [

      Fleet J, Guha K, Piper S, Banya W, Bilton D, Hodson ME. A retrospective analysis of the impact of azithromycin maintenance therapy on adults attending a UK cystic fibrosis clinic. J Cyst Fibros in press, http://dx.doi.org/10.1016/j.jcf.2012.05.010.

      ].

      8.6 Anaerobic species

      The potential role for anaerobic species in the pathogenesis of CF airways disease has become of greater interest as culture-independent analysis of CF respiratory specimens has revealed the presence of strict anaerobic species [
      • Tunney M.M.
      • Klem E.R.
      • Fodor A.A.
      • Gilpin D.F.
      • Moriarty T.F.
      • McGrath S.J.
      • et al.
      Use of culture and molecular analysis to determine the effect of antibiotic treatment on microbial community diversity and abundance during exacerbation in patients with cystic fibrosis.
      ,
      • Tunney M.M.
      • Field T.R.
      • Moriarty T.F.
      • Patrick S.
      • Doering G.
      • Muhlebach M.S.
      • et al.
      Detection of anaerobic bacteria in high numbers in sputum from patients with cystic fibrosis.
      ,
      • Rogers G.B.
      • Hart C.A.
      • Mason J.R.
      • Hughes M.
      • Walshaw M.J.
      • Bruce K.D.
      Bacterial diversity in cases of lung infection in cystic fibrosis patients: 16S ribosomal DNA (rDNA) length heterogeneity PCR and 16S rDNA terminal restriction fragment length polymorphism profiling.
      ,
      • Rogers G.B.
      • Carroll M.P.
      • Serisier D.J.
      • Hockey P.M.
      • Jones G.
      • Bruce K.D.
      Characterization of bacterial community diversity in cystic fibrosis lung infections by use of 16s ribosomal DNA terminal restriction fragment length polymorphism profiling.
      ,
      • Rogers G.B.
      • Carroll M.P.
      • Serisier D.J.
      • Hockey P.M.
      • Jones G.
      • Kehagia V.
      • et al.
      Use of 16S rRNA gene profiling by terminal restriction fragment length polymorphism analysis to compare bacterial communities in sputum and mouthwash samples from patients with cystic fibrosis.
      ,
      • Sibley C.D.
      • Duan K.
      • Fischer C.
      • Parkins M.D.
      • Storey D.G.
      • Rabin H.R.
      • et al.
      Discerning the complexity of community interactions using a Drosophila model of polymicrobial infections.
      ]. Many strict anaerobic bacteria are antibiotic resistant [
      • Tunney M.M.
      • Field T.R.
      • Moriarty T.F.
      • Patrick S.
      • Doering G.
      • Muhlebach M.S.
      • et al.
      Detection of anaerobic bacteria in high numbers in sputum from patients with cystic fibrosis.
      ,
      • Worlitzsch D.
      • Rintelen C.
      • Bohm K.
      • Wollschläger B.
      • Merkel N.
      • Borneff-Lipp M.
      • et al.
      Antibiotic-resistant obligate anaerobes during exacerbations of cystic fibrosis patients.
      ]. Studies show that a higher diversity of strict anaerobes is associated with a younger age [
      • Cox M.J.
      • Allgaier M.
      • Taylor B.
      • Baek M.S.
      • Huang Y.J.
      • Daly R.A.
      • et al.
      Airway microbiota and pathogen abundance in age-stratified cystic fibrosis patients.
      ], and better lung function [
      • Klepac-Ceraj V.
      • Lemon K.P.
      • Martin T.R.
      • Allgaier M.
      • Kembel S.V.
      • Knapp A.A.
      • et al.
      Relationship between cystic fibrosis respiratory tract bacterial communities and age, genotype, antibiotics and Pseudomonas aeruginosa.
      ]. The major reason why clinicians have not specifically treated anaerobes is because the clinical significance of these species remains unclear. For Prevotella intermedia, however, in vitro data suggest that the pathogen may contribute to lung disease in CF patients [
      • Ulrich M.
      • Beer I.
      • Braitmaier P.
      • Dierkes M.
      • Kummer F.
      • Krismer B.
      • et al.
      Relative contribution of Prevotella intermedia and Pseudomonas aeruginosa to lung pathology in airways of cystic fibrosis patients.
      ]. The demonstration that P. intermedia produces cytotoxins and provokes inflammation in vitro suggests that it causes airway damage, which if demonstrated in vivo would facilitate the decision for antibiotic treatment.

      8.7 Other microbial pathogens

      Other commonly identified microbial pathogens present in airways of CF patients include Aspergillus fumigatus, for which increasing prevalence is clearly associated with the use of inhaled antibiotics [
      • De Vrankrijker A.M.
      • van der Ent C.K.
      • van Berkhout F.T.
      • Stellato R.K.
      • Willems R.J.
      • Bonten M.J.
      • et al.
      Aspergillus fumigatus colonization in cystic fibrosis: implications for lung function?.
      ]. A. fumigatus may cause severe endobronchial infections and allergic bronchopulmonary aspergillosis (ABPA) in 2–7.8% of CF patients [
      • Geller D.E.
      • Kaplowitz H.
      • Light M.J.
      • Colin A.A.
      Allergic bronchopulmonary aspergillosis in cystic fibrosis: reported prevalence, regional distribution, and patient characteristics.
      ,
      • Mastella G.
      • Rainisio M.
      • Harms H.K.
      • Hodson M.E.
      • Koch C.
      • Navarro J.
      • et al.
      Allergic bronchopulmonary aspergillosis in cystic fibrosis. A European epidemiological study.
      ].
      In summary, the presence of many other bacterial species besides P. aeruginosa in CF airways may represent a target for therapy, because they are either directly pathogenic or they may increase the virulence of other pathogens [
      • Sibley C.D.
      • Parkins M.D.
      • Rabin H.R.
      • Duan K.
      • Norgaard J.C.
      • Surette M.G.
      A polymicrobial perspective of pulmonary infections exposes an enigmatic pathogen in cystic fibrosis patients.
      ] or inhibit antibiotics thereby diluting their effects on P. aeruginosa [
      • Rogers G.B.
      • Marsh P.
      • Stressmann A.F.
      • Allen C.E.
      • Daniels T.V.W.
      • Carroll M.P.
      • et al.
      The exclusion of dead bacterial cells is essential for accurate molecular analysis of clinical samples.
      ]. The path from identification of the organism to management decisions requires epidemiological studies that demonstrate the role the organism plays in the pathogenesis of disease and the observation of clinical benefit from treatment interventions designated specifically at the pathogen. Early epidemiological studies of these pathogens have begun to inform us that these are indeed pathogens, but we lack clinical studies of intervention and such studies are clearly needed.

      9. Comparative efficacy of inhaled antibiotics in CF and endpoints in clinical trials

      There is a perceived need for additional antibiotic choices for the management of CF airways disease. As there are no new antibiotic classes being developed, new options for inhaled antibiotics are the most likely new development and some have been discussed earlier (Section 5). The clinical need is due to the fact that some patients cannot tolerate current available options, they have become refractory to the current therapy or the treatment burden results in poor adherence and thus, reduced efficacy [
      • Eakin M.N.
      • Bilderback A.
      • Boyle M.P.
      • Mogayzel P.J.
      • Riekert K.A.
      Longitudinal association between medication adherence and lung health in people with cystic fibrosis.
      ,
      • Modi A.C.
      • Quittner A.L.
      Barriers to treatment adherence for children with cystic fibrosis and asthma: what gets in the way?.
      ,
      • Sawicki G.S.
      • Rasouliyan L.R.
      • McMullen A.H.
      • Wagener J.S.
      • McColley S.A.
      • Pasta D.J.
      • et al.
      Longitudinal assessment of health-related quality of life in an observational cohort of patients with cystic fibrosis.
      ]. Technological advances, such as faster and smarter nebulizers and dry powder formulations, offer great opportunity, but there is also a need for additional drug classes, as current approved formulations include only an aminoglycoside, a monobactam, and a polymyxin.
      The challenge to further development of new aerosol antibiotic options is how best to study them. In general, the clinical trials for developing new inhaled antibiotics are designed either as superiority studies versus placebo. However, when such studies require extended periods of no antibiotic, they are no longer considered ethical for patients. Although non-inferiority studies can be performed, given the relatively small treatment benefits it is difficult to agree on an optimal non-inferiority margins. Non-inferiority trials typically require large numbers of patients making such studies more difficult to conduct.
      In the light of novel antibiotic formulations for CF patients, which bring important patient benefits for the same clinical efficacy, as reported in clinical trials, it is important to further discuss how these benefits can be valued and included in a comparative effectiveness research reflecting real-life benefits. In the context of a clinical trial setting, the patients' adherence is generally high, whereas in the real-world, rates of adherence and persistence rates are much lower and the efficacy of a drug can be therefore decreased [
      • Eakin M.N.
      • Bilderback A.
      • Boyle M.P.
      • Mogayzel P.J.
      • Riekert K.A.
      Longitudinal association between medication adherence and lung health in people with cystic fibrosis.