Pulmonary outcome in cystic fibrosis is influenced primarily by mucoid Pseudomonas aeruginosa infection and immune status and only modestly by genotype

Antibiotic strategies for eradicating Pseudomonas aeruginosa in people with cystic fibrosis

BACKGROUND

Respiratory tract infections with Pseudomonas aeruginosa occur in most people with cystic fibrosis (CF). Established chronic P aeruginosa infection is virtually impossible to eradicate and is associated with increased mortality and morbidity. Early infection may be easier to eradicate. This is an updated review.

OBJECTIVES

Does giving antibiotics for P aeruginosa infection in people with CF at the time of new isolation improve clinical outcomes (e.g. mortality, quality of life and morbidity), eradicate P aeruginosa infection, and delay the onset of chronic infection, but without adverse effects, compared to usual treatment or an alternative antibiotic regimen? We also assessed cost-effectiveness.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and conference proceedings. Latest search: 24 March 2022. We searched ongoing trials registries. Latest search: 6 April 2022.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of people with CF, in whom P aeruginosa had recently been isolated from respiratory secretions. We compared combinations of inhaled, oral or intravenous (IV) antibiotics with placebo, usual treatment or other antibiotic combinations. We excluded non-randomised trials and cross-over trials.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials, assessed risk of bias and extracted data. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included 11 trials (1449 participants) lasting between 28 days and 27 months; some had few participants and most had relatively short follow-up periods. Antibiotics in this review are: oral - ciprofloxacin and azithromycin; inhaled - tobramycin nebuliser solution for inhalation (TNS), aztreonam lysine (AZLI) and colistin; IV - ceftazidime and tobramycin. There was generally a low risk of bias from missing data. In most trials it was difficult to blind participants and clinicians to treatment. Two trials were supported by the manufacturers of the antibiotic used. TNS versus placebo TNS may improve eradication; fewer participants were still positive for P aeruginosa at one month (odds ratio (OR) 0.06, 95% confidence interval (CI) 0.02 to 0.18; 3 trials, 89 participants; low-certainty evidence) and two months (OR 0.15, 95% CI 0.03 to 0.65; 2 trials, 38 participants). We are uncertain whether the odds of a positive culture decrease at 12 months (OR 0.02, 95% CI 0.00 to 0.67; 1 trial, 12 participants). TNS (28 days) versus TNS (56 days) One trial (88 participants) comparing 28 days to 56 days TNS treatment found duration of treatment may make little or no difference in time to next isolation (hazard ratio (HR) 0.81, 95% CI 0.37 to 1.76; low-certainty evidence). Cycled TNS versus culture-based TNS One trial (304 children, one to 12 years old) compared cycled TNS to culture-based therapy and also ciprofloxacin to placebo. We found moderate-certainty evidence of an effect favouring cycled TNS therapy (OR 0.51, 95% CI 0.31 to 0.82), although the trial publication reported age-adjusted OR and no difference between groups. Ciprofloxacin versus placebo added to cycled and culture-based TNS therapy One trial (296 participants) examined the effect of adding ciprofloxacin versus placebo to cycled and culture-based TNS therapy. There is probably no difference between ciprofloxacin and placebo in eradicating P aeruginosa (OR 0.89, 95% CI 0.55 to 1.44; moderate-certainty evidence). Ciprofloxacin and colistin versus TNS We are uncertain whether there is any difference between groups in eradication of P aeruginosa at up to six months (OR 0.43, 95% CI 0.15 to 1.23; 1 trial, 58 participants) or up to 24 months (OR 0.76, 95% CI 0.24 to 2.42; 1 trial, 47 participants); there was a low rate of short-term eradication in both groups. Ciprofloxacin plus colistin versus ciprofloxacin plus TNS One trial (223 participants) found there may be no difference in positive respiratory cultures at 16 months between ciprofloxacin with colistin versus TNS with ciprofloxacin (OR 1.28, 95% CI 0.72 to 2.29; low-certainty evidence). TNS plus azithromycin compared to TNS plus oral placebo Adding azithromycin may make no difference to the number of participants eradicating P aeruginosa after a three-month treatment phase (risk ratio (RR) 1.01, 95% CI 0.75 to 1.35; 1 trial, 91 participants; low-certainty evidence); there was also no evidence of any difference in the time to recurrence. Ciprofloxacin and colistin versus no treatment A single trial only reported one of our planned outcomes; there were no adverse effects in either group. AZLI for 14 days plus placebo for 14 days compared to AZLI for 28 days We are uncertain whether giving 14 or 28 days of AZLI makes any difference to the proportion of participants having a negative respiratory culture at 28 days (mean difference (MD) -7.50, 95% CI -24.80 to 9.80; 1 trial, 139 participants; very low-certainty evidence). Ceftazidime with IV tobramycin compared with ciprofloxacin (both regimens in conjunction with three months colistin) IV ceftazidime with tobramycin compared with ciprofloxacin may make little or no difference to eradication of P aeruginosa at three months, sustained to 15 months, provided that inhaled antibiotics are also used (RR 0.84, 95 % CI 0.65 to 1.09; P = 0.18; 1 trial, 255 participants; high-certainty evidence). The results do not support using IV antibiotics over oral therapy to eradicate P aeruginosa, based on both eradication rate and financial cost.

AUTHORS' CONCLUSIONS

We found that nebulised antibiotics, alone or with oral antibiotics, were better than no treatment for early infection with P aeruginosa. Eradication may be sustained in the short term. There is insufficient evidence to determine whether these antibiotic strategies decrease mortality or morbidity, improve quality of life, or are associated with adverse effects compared to placebo or standard treatment. Four trials comparing two active treatments have failed to show differences in rates of eradication of P aeruginosa. One large trial showed that intravenous ceftazidime with tobramycin is not superior to oral ciprofloxacin when inhaled antibiotics are also used. There is still insufficient evidence to state which antibiotic strategy should be used for the eradication of early P aeruginosa infection in CF, but there is now evidence that intravenous therapy is not superior to oral antibiotics.

How Three Self-Secreted Biofilm Exopolysaccharides of Pseudomonas aeruginosa, Psl, Pel, and Alginate, Can Each Be Exploited for Antibiotic Adjuvant Effects in Cystic Fibrosis Lung Infection

In cystic fibrosis (CF), pulmonary infection with Pseudomonas aeruginosa is a cause of increased morbidity and mortality, especially in patients for whom infection becomes chronic and there is reliance on long-term suppressive therapies. Current antimicrobials, though varied mechanistically and by mode of delivery, are inadequate not only due to their failure to eradicate infection but also because they do not halt the progression of lung function decline over time. One of the reasons for this failure is thought to be the biofilm mode of growth of P. aeruginosa, wherein self-secreted exopolysaccharides (EPSs) provide physical protection against antibiotics and an array of niches with resulting metabolic and phenotypic heterogeneity. The three biofilm-associated EPSs secreted by P. aeruginosa (alginate, Psl, and Pel) are each under investigation and are being exploited in ways that potentiate antibiotics. In this review, we describe the development and structure of P. aeruginosa biofilms before examining each EPS as a potential therapeutic target for combating pulmonary infection with P. aeruginosa in CF, with a particular focus on the current evidence for these emerging therapies and barriers to bringing these therapies into clinic.

Severe Scalp Psoriasis Microbiome Has Increased Biodiversity and Relative Abundance of Pseudomonas Compared to Mild Scalp Psoriasis

Psoriasis is a chronic inflammatory skin disease associated with various factors. Recently, alterations in the gut and skin microbiomes have been shown to interact with host immunity, affect skin barrier function, as well as development and progression of psoriasis. We aimed to analyze the microbiota of the scalp of patients with psoriasis and determine the characteristics of the microbiome according to disease severity. We investigated the scalp microbiome of 39 patients with psoriasis scalp lesions and a total of 47 samples were analyzed. The patients were divided into mild, moderate, and severe groups according to the European recommendations for scalp psoriasis. For bacterial identification, we utilized the SILVA database targeting the V3 region of the 16 S rRNA gene. The mean Shannon index escalated along with disease severity, and the diversity of the scalp microbiome tended to increase with disease severity (R = 0.37, p < 0.01). The relative abundance of Pseudomonas was increased in severe scalp psoriasis (0.49 ± 0.22) compared to the mild group (0.07 ± 0.03, p = 0.029), and Diaphorobacter was enriched in the mild group (0.76 ± 0.16%) compared to the severe group (0.44 ± 0.22, p < 0.001). We identified that increased diversity of the scalp microbiome and the relative abundance of Pseudomonas are associated with the severity of scalp psoriasis.

Adaptation and Evolution of Pathogens in the Cystic Fibrosis Lung

As opposed to acute respiratory infections, the persistent bacterial infections of the lung that characterize cystic fibrosis (CF) provide ample time for bacteria to evolve and adapt. The process of adaptation is recorded in mutations that accumulate over time in the genomes of the infecting bacteria. Some of these mutations lead to obvious phenotypic differences such as antibiotic resistance or the well-known mucoid phenotype of Pseudomonas aeruginosa. Other mutations may be just as important but harder to detect such as increased mutation rates, cell surface changes, and shifts in metabolism and nutrient acquisition. Remarkably, many of the adaptations occur again and again in different patients, signaling that bacteria are adapting to solve specific challenges in the CF respiratory tract. This parallel evolution even extends across distinct bacterial species. This review addresses the bacterial systems that are known to change in long-term CF infections with a special emphasis on cross-species comparisons. Consideration is given to how adaptation may impact health in CF, and the possible evolutionary mechanisms that lead to the repeated parallel adaptations.

The anti-sigma factor MucA is required for viability in Pseudomonas aeruginosa

During decades-long infections in the cystic fibrosis (CF) airway, Pseudomonas aeruginosa undergoes selection. One bacterial genetic adaptation often observed in CF isolates is mucA mutations. MucA inhibits the sigma factor AlgU. Mutations in mucA lead to AlgU misregulation, resulting in a mucoid phenotype that is associated with poor CF disease outcomes. Due to its ability to be mutated, mucA is assumed to be dispensable for bacterial viability. Here we show that, paradoxically, a portion of mucA is essential in P. aeruginosa. We demonstrate that mucA is no longer required in a strain lacking algU, that mucA alleles encoding for proteins that do not bind to AlgU are insufficient for viability, and that mucA is no longer essential in mutant strains containing AlgU variants with reduced sigma factor activity. Furthermore, we found that overexpression of algU prevents cell growth in the absence of MucA, and that this phenotype can be rescued by the overproduction of RpoD, the housekeeping sigma factor. Together, these results suggest that in the absence of MucA, the inability to regulate AlgU activity results in the loss of bacterial viability. Finally, we speculate that the essentiality of anti-sigma factors that regulate envelope function may be a widespread phenomenon in bacteria.

From genotype to phenotype: adaptations of Pseudomonas aeruginosa to the cystic fibrosis environment

Pseudomonas aeruginosa is one of the main microbial species colonizing the lungs of cystic fibrosis patients and is responsible for the decline in respiratory function. Despite the hostile pulmonary environment, P. aeruginosa is able to establish chronic infections thanks to its strong adaptive capacity. Various longitudinal studies have attempted to compare the strains of early infection with the adapted strains of chronic infection. Thanks to new '-omics' techniques, convergent genetic mutations, as well as transcriptomic and proteomic dysregulations have been identified. As a consequence of this evolution, the adapted strains of P. aeruginosa have particular phenotypes that promote persistent infection.

Cystic Fibrosis and Pseudomonas aeruginosa: the Host-Microbe Interface

In human pathophysiology, the clash between microbial infection and host immunity contributes to multiple diseases. Cystic fibrosis (CF) is a classical example of this phenomenon, wherein a dysfunctional, hyperinflammatory immune response combined with chronic pulmonary infections wreak havoc upon the airway, leading to a disease course of substantial morbidity and shortened life span. Pseudomonas aeruginosa is an opportunistic pathogen that commonly infects the CF lung, promoting an accelerated decline of pulmonary function. Importantly, P. aeruginosa exhibits significant resistance to innate immune effectors and to antibiotics, in part, by expressing specific virulence factors (e.g., antioxidants and exopolysaccharides) and by acquiring adaptive mutations during chronic infection. In an effort to review our current understanding of the host-pathogen interface driving CF pulmonary disease, we discuss (i) the progression of disease within the primitive CF lung, specifically focusing on the role of host versus bacterial factors; (ii) critical, neutrophil-derived innate immune effectors that are implicated in CF pulmonary disease, including reactive oxygen species (ROS) and antimicrobial peptides (e.g., LL-37); (iii) P. aeruginosa virulence factors and adaptive mutations that enable evasion of the host response; and (iv) ongoing work examining the distribution and colocalization of host and bacterial factors within distinct anatomical niches of the CF lung.

Mucoid Pseudomonas aeruginosa and regional inflammation in the cystic fibrosis lung

BACKGROUND

Pseudomonas aeruginosa is the prominent bacterial pathogen in the cystic fibrosis (CF) lung and contributes to significant morbidity and mortality. Though P. aeruginosa strains initially colonizing the CF lung have a nonmucoid colony morphology, they often mutate into mucoid variants that are associated with clinical deterioration. Both nonmucoid and mucoid P. aeruginosa variants are often co-isolated on microbiological cultures of sputum collected from CF patients. With regional variation in bronchiectasis, tissue damage, inflammation, and microbial colonization, lobar distribution of nonmucoid and mucoid P. aeruginosa variants may impact local microenvironments in the CF lung, but this has not been well-studied.

METHODS

We prospectively collected lobe-specific bronchoalveolar lavage (BAL) fluid from a CF patient cohort (n = 14) using a standardized bronchoscopic protocol where collection was performed in 6 lobar regions. The lobar BAL specimens were plated on P. aeruginosa-selective media and proinflammatory cytokines (IL-1, TNF, IL-6 and IL-8) were measured via cytokine array. Correlations between infecting P. aeruginosa variants (nonmucoid, mucoid, or mixed-variant populations), the lobar regions in which these variants were found, and regional proinflammatory cytokine concentrations were measured.

RESULTS

P. aeruginosa mucoid and nonmucoid variants were homogenously distributed throughout the CF lung. However, infection with mucoid variants (found within single- or mixed-variant populations) was associated with significantly greater regional inflammation. The upper and lower lobes of the CF lung did not exhibit differences in inflammatory cytokine concentrations.

CONCLUSIONS

Mucoid P. aeruginosa infection is a microbial determinant of regional inflammation within the CF lung.

Genetic Association of Pulmonary Surfactant Protein Genes, SFTPA1, SFTPA2, SFTPB, SFTPC, and SFTPD With Cystic Fibrosis

Surfactant proteins (SP) are involved in surfactant function and innate immunity in the human lung. Both lung function and innate immunity are altered in CF, and altered SP levels and genetic association are observed in Cystic Fibrosis (CF). We hypothesized that single nucleotide polymorphisms (SNPs) within the SP genes associate with CF or severity subgroups, either through single SNP or via SNP-SNP interactions between two SNPs of a given gene (intragenic) and/or between two genes (intergenic). We genotyped a total of 17 SP SNPs from 72 case-trio pedigree (SFTPA1 (5), SFTPA2 (4), SFTPB (4), SFTPC (2), and SFTPD (2)), and identified SP SNP associations by applying quantitative genetic principles. The results showed (a) Two SNPs, SFTPB rs7316 (p = 0.0083) and SFTPC rs1124 (p = 0.0154), each associated with CF. (b) Three intragenic SNP-SNP interactions, SFTPB (rs2077079, rs3024798), and SFTPA1 (rs1136451, rs1059057 and rs4253527), associated with CF. (c) A total of 34 intergenic SNP-SNP interactions among the 4 SP genes to be associated with CF. (d) No SNP-SNP interaction was observed between SFTPA1 or SFTPA2 and SFTPD. (e) Equal number of SNP-SNP interactions were observed between SFTPB and SFTPA1/SFTPA2 (n = 7) and SP-B and SFTPD (n = 7). (f) SFTPC exhibited significant SNP-SNP interactions with SFTPA1/SFTPA2 (n = 11), SFTPB (n = 4) and SFTPD (n = 3). (g) A single SFTPB SNP was associated with mild CF after Bonferroni correction, and several intergenic interactions that are associated (p < 0.01) with either mild or moderate/severe CF were observed. These collectively indicate that complex SNP-SNP interactions of the SP genes may contribute to the pulmonary disease in CF patients. We speculate that SPs may serve as modifiers for the varied progression of pulmonary disease in CF and/or its severity.

Antibiotic resistance evolution of Pseudomonas aeruginosa in cystic fibrosis patients (2010-2013)

INTRODUCTION

Pseudomonas aeruginosa is the predominant pathogen responsible of chronic colonization of the airways in cystic fibrosis (CF) patients. There are few European data about antibiotic susceptibility evolution of P aeruginosa in CF patients.

OBJECTIVES

The aim of this study is to evaluate the evolution of antibiotic resistance in the period 2010-2013 in CF patients chronically colonized by P aeruginosa and to highlight the characteristics of this evolution in patients younger than 20 years.

METHODS

Clinical and microbiological data were extracted from two electronic databases and analyzed. Antibiotic resistance was defined according to European Committee of Antimicrobial Susceptibility Testing for levofloxacin, ciprofloxacin, meropenem, amikacin and ceftazidime. The between-group comparison was drawn with the Chi-square test for proportions, with the T-test for unpaired samples for normally distributed data and with Mann-Whitney test for non-normally distributed data. Significancy was defined by P < .05.

RESULTS

Fifty-seven CF patients, including thirteen subjects aged less than 20 years, were enrolled. P.. aeruginosa antibiotic sensitivity decreased significantly for fluoroquinolones, mainly in patients aged <20 years, while it increased for amikacin and colistin. The analysis of minimum inhibitory concentration confirmed these trends. In pediatric patients treated with more than three antibiotic cycles per year, greater resistance was found, except for amikacin and colistin.

CONCLUSION

An evolution in P aeruginosa antibiotic resistances is observed in the 4-year period studied. Responsible and informed use of antibiotics is mandatory in CF.

Combination antibiotics against Pseudomonas aeruginosa, representing common and rare cystic fibrosis strains from different Irish clinics

Objectives

To evaluate the effect of antibiotic combination therapy versus single therapy against cystic fibrosis strains of Pseudomonas aeruginosa identified as common and rare among patient groups in different Irish hospitals.

Methods

This study compares the susceptibility profiles of P. aeruginosa isolates from different cystic fibrosis (CF) clinics in Ireland, collected from 2004–2005. Strains were recovered in small numbers and typed by pulsed-field gel electrophoresis. Five common clonal variants were identified in five different hospitals, described as ‘common strains’. A number of ‘rare strains’ associated with any single patient were also included in the study. Certain virulence factors were determined and in vitro assays such as minimum inhibitory concentrations (MIC) and biofilm inhibitory concentrations (BIC) were employed to assess potential synergistic effects of antipseudomonal antibiotic combination therapy.

Results

There was no distinct virulence factors associated with clinical strains that were common in comparison to those that were rare. Antibiotic combination testing revealed the majority of combinations were similar to the activity of either antibiotic used as single agents. Tobramycin-ceftazidime was the most effective combination exhibiting synergistic interactions (FIC ≤ 0.5) against certain clinical isolates of P. aeruginosa.

Conclusion

The efficacy of single antibiotics and synergistic interactions of antibiotic combinations were strain specific, irrespective of virulence characteristics of P. aeruginosa. Common clonal P. aeruginosa strains do not have distinct characteristics that possibly influence persistence in the chronic CF lung. Tobramycin-ceftazidime may be successful for controlling specific P. aeruginosa strains. Further studies on representative isolates are needed to support these results.

Antibiotic perturbation of mixed-strain Pseudomonas aeruginosa infection in patients with cystic fibrosis

Background

Pulmonary exacerbations in cystic fibrosis (CF) remain poorly understood and treatment is usually targeted at Pseudomonas aeruginosa. Within Australia a predominant shared P. aeruginosa strain (AUST-02) is associated with greater treatment needs. This single centre study assessed temporal shared strain population dynamics during and after antibiotic treatment of exacerbations.

Methods

Sputum was collected from 12 adult patients with a history of chronic AUST-02 infection at four time-points during and after treatment of an exacerbation. Forty-eight P. aeruginosa isolates within each sample underwent AUST-02 allele-specific PCR and SNP-based strain genotyping.

Results

Various commonly shared Australian strains (AUST-01, 0.1%; AUST-02, 54.3%; AUST-06, 36.6%; AUST-07, 4.6%; AUST-11, 4.3%) and two unique strains (0.1%) were identified from 45 sputum samples (2160 isolates). Based on within-patient relative abundance of strains, a “single-strain infection” (n = 7) or “mixed-strain infection” (n = 5) was assigned to each patient. A significant temporal variation in the P. aeruginosa population composition was found for those with mixed-strain infection (P < 0.001). Patients with mixed-strain infections had more long-term treatment requirements than those with single-strain infection. Moreover, despite both groups having similar lung function at study entry, patients with single-strain infection had greater improvement in FEV₁% predicted following their exacerbation treatment (P = 0.02).

Conclusion

Pulmonary exacerbations may reveal multiple, unrelated P. aeruginosa strains whose relative abundance with one another may change rapidly, in a sustained and unpredictable manner.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0482-7) contains supplementary material, which is available to authorized users.

Time-Kill Analysis of Ceftolozane/Tazobactam Efficacy Against Mucoid Pseudomonas aeruginosa Strains from Cystic Fibrosis Patients

INTRODUCTION

Mucoid Pseudomonas aeruginosa (MP) strains in cystic fibrosis (CF) patients are thought to initiate the chronic infection stage of CF and are associated with pulmonary function decline.

OBJECTIVES

The purpose of this study was to assess the susceptibility of MP strains to ceftolozane/tazobactam and the efficacy of ceftolozane/tazobactam against MP strains compared with those for standard-of-care antipseudomonal antibiotics.

METHODS

Ten clinical isolates of MP from CF patients were tested for susceptibility with Etest and time-kill analysis with ceftolozane/tazobactam compared with ceftazidime, cefepime, ciprofloxacin, meropenem, tobramycin, and polymyxin B. The physiologic free peak concentrations were used in the time-kill experiments.

RESULTS

Ceftolozane/tazobactam minimum inhibitory concentrations ranged from 0.032 to 1.5 mg/L. In the time-kill analysis, the mean starting inoculum for the isolates was 6.29 ± 0.22 log₁₀ colony forming units (CFU) per milliliter. On average, ceftolozane/tazobactam, cefepime, ciprofloxacin, meropenem, tobramycin, and polymyxin B all demonstrated bactericidal activity. With all isolates taken into account, polymyxin B, tobramycin, meropenem, and ceftolozane/tazobactam 3 g were the most potent, with reductions in inoculum of 5.07 ± 0.45, 4.58 ± 2.2, 4.76 ± 0.71, and 4.17 ± 0.94 log₁₀ CFU/mL, respectively. Ceftolozane/tazobactam 1.5 g, cefepime, and ciprofloxacin reduced the starting inoculum by 3.74 ± 0.99, 3.42 ± 1.4, and 3.23 ± 2.0 log₁₀ CFU/mL, respectively. Despite 90% susceptibility, ceftazidime was bactericidal against seven of ten strains, with an average reduction in starting inoculum of 2.91 ± 2.2 log₁₀ CFU/mL.

CONCLUSION

Ceftolozane/tazobactam activity against MP strains derived from CF patients was comparable to that of standard-of-care agents at both the 1.5-g dose and the 3-g dose. Further in vitro modeling and clinical trials are warranted.

Incident Stenotrophomonas maltophilia infection and lung function decline in cystic fibrosis

OBJECTIVES

To determine whether incident detection of Stenotrophomonas maltophilia (SM) in patients with cystic fibrosis (CF) is associated with accelerated lung function decline and increased hospitalizations and to determine whether this effect is more pronounced in individuals with subsequent chronic infection.

METHODS

We performed a longitudinal, retrospective single-center, pre-post study of 88 patients with CF, ages 6-51 years, with first positive respiratory culture for SM between 2008 and 2014. Rate of decline in FEV₁ and hospitalization rates prior to and following incident SM infection were analyzed using segmented regression analysis of interrupted time series.

RESULTS

Mean (SD) age was 17.4 (9.2) years and the mean (SD) FEV₁ % predicted at acquisition was 90.0% (25.2). A total of 44% developed chronic SM infection. In regression analysis adjusted for clinical and demographic factors, there was worsening of the mean annual decline in FEV₁ % predicted from -1.79 (95%CI: -2.43, -1.15) pre-acquisition to -2.14 (95%CI: -2.61, -1.67) post-acquisition (P = 0.005). A significant change was observed in those with either subsequent intermittent or chronic infection. The mean annual hospitalization rate increased significantly in the subgroup with chronic infection from 0.46 (95%CI: 0.33, 0.60) to 0.88 (95%CI: 0.68, 1.07) (P = 0.007).

CONCLUSIONS

In this single-center cohort, acquisition of SM in CF was associated with an acceleration in lung function decline. Among those with chronic colonization, acquisition was also associated with increased hospitalization rates.

Relevance of multidrug-resistant Pseudomonas aeruginosa infections in cystic fibrosis

Multidrug-resistant (MDR) Pseudomonas aeruginosa is an important issue for physicians who take care of patients with cystic fibrosis (CF). Here, we review the latest research on how P. aeruginosa infection causes lung function to decline and how several factors contribute to the emergence of antibiotic resistance in P. aeruginosa strains and influence the course of the infection course. However, many aspects of the practical management of patients with CF infected with MDR P. aeruginosa are still to be established. Less is known about the exact role of susceptibility testing in clinical strategies for dealing with resistant infections, and there is an urgent need to find a tool to assist in choosing the best therapeutic strategy for MDR P. aeruginosa infection. One current perception is that the selection of antibiotic therapy according to antibiogram results is an important component of the decision-making process, but other patient factors, such as previous infection history and antibiotic courses, also need to be evaluated. On the basis of the known issues and the best current data on respiratory infections caused by MDR P. aeruginosa, this review provides practical suggestions to optimize the diagnostic and therapeutic management of patients with CF who are infected with these pathogens.

Antibiotic strategies for eradicating Pseudomonas aeruginosa in people with cystic fibrosis

BACKGROUND

Respiratory tract infection with Pseudomonas aeruginosa occurs in most people with cystic fibrosis. Once chronic infection is established, Pseudomonas aeruginosa is virtually impossible to eradicate and is associated with increased mortality and morbidity. Early infection may be easier to eradicate.This is an update of a Cochrane review first published in 2003, and previously updated in 2006, 2009 and 2014.

OBJECTIVES

To determine whether antibiotic treatment of early Pseudomonas aeruginosa infection in children and adults with cystic fibrosis eradicates the organism, delays the onset of chronic infection, and results in clinical improvement. To evaluate whether there is evidence that a particular antibiotic strategy is superior to or more cost-effective than other strategies and to compare the adverse effects of different antibiotic strategies (including respiratory infection with other micro-organisms).

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Most recent search: 10 October 2016.

SELECTION CRITERIA

We included randomised controlled trials of people with cystic fibrosis, in whom Pseudomonas aeruginosa had recently been isolated from respiratory secretions. We compared combinations of inhaled, oral or intravenous antibiotics with placebo, usual treatment or other combinations of inhaled, oral or intravenous antibiotics. We excluded non-randomised trials, cross-over trials, and those utilising historical controls.

DATA COLLECTION AND ANALYSIS

Both authors independently selected trials, assessed risk of bias and extracted data.

MAIN RESULTS

The search identified 60 trials; seven trials (744 participants) with a duration between 28 days and 27 months were eligible for inclusion. Three of the trials are over 10 years old and their results may be less applicable today given the changes in standard treatment. Some of the trials had low numbers of participants and most had relatively short follow-up periods; however, there was generally a low risk of bias from missing data. In most trials it was difficult to blind participants and clinicians to treatment given the interventions and comparators used. Two trials were supported by the manufacturers of the antibiotic used.Evidence from two trials (38 participants) at the two-month time-point showed treatment of early Pseudomonas aeruginosa infection with inhaled tobramycin results in microbiological eradication of the organism from respiratory secretions more often than placebo, odds ratio 0.15 (95% confidence interval (CI) 0.03 to 0.65) and data from one of these trials, with longer follow up, suggested that this effect may persist for up to 12 months.One randomised controlled trial (26 participants) compared oral ciprofloxacin and nebulised colistin versus usual treatment. Results after two years suggested treatment of early infection results in microbiological eradication of Pseudomonas aeruginosa more often than no anti-pseudomonal treatment, odds ratio 0.12 (95% CI 0.02 to 0.79).One trial comparing 28 days to 56 days treatment with nebulised tobramycin solution for inhalation in 88 participants showed that both treatments were effective and well-tolerated, with no notable additional improvement with longer over shorter duration of therapy. However, this trial was not powered to detect non-inferiority or equivalence .A trial of oral ciprofloxacin with inhaled colistin versus nebulised tobramycin solution for inhalation alone (223 participants) failed to show a difference between the two strategies, although it was underpowered to show this. A further trial of inhaled colistin with oral ciprofloxacin versus nebulised tobramycin solution for inhalation with oral ciprofloxacin also showed no superiority of the former, with increased isolation of Stenotrophomonas maltophilia in both groups.A recent, large trial in 306 children aged between one and 12 years compared cycled nebulised tobramycin solution for inhalation to culture-based therapy and also ciprofloxacin to placebo. The primary analysis showed no difference in time to pulmonary exacerbation or proportion of Pseudomonas aeruginosa positive cultures. An analysis performed in this review (not adjusted for age) showed fewer participants in the cycled therapy group with one or more isolates of Pseudomonas aeruginosa, odds ratio 0.51 (95% CI 0.31 to 0.28). Using GRADE, the quality of evidence for outcomes was downgraded to moderate to very low. Downgrading decisions for Pseudomonas aeruginosa eradication and lung function were based on applicability (participants mostly children) and limitations in study design, with imprecision an additional limitation for lung function, growth parameters and adverse effects.

AUTHORS' CONCLUSIONS

We found that nebulised antibiotics, alone or in combination with oral antibiotics, were better than no treatment for early infection with Pseudomonas aeruginosa. Eradication may be sustained for up to two years. There is insufficient evidence to determine whether antibiotic strategies for the eradication of early Pseudomonas aeruginosa decrease mortality or morbidity, improve quality of life, or are associated with adverse effects compared to placebo or standard treatment. Four trials comparing two active treatments have failed to show differences in rates of eradication of Pseudomonas aeruginosa. There have been no published randomised controlled trials that investigate the efficacy of intravenous antibiotics to eradicate Pseudomonas aeruginosa in cystic fibrosis. Overall, there is still insufficient evidence from this review to state which antibiotic strategy should be used for the eradication of early Pseudomonas aeruginosa infection in cystic fibrosis.

Change in Pseudomonas aeruginosa prevalence in cystic fibrosis adults over time

Background

Little is known about risk factors for chronic and mucoid Pseudomonas aeruginosa (Pa) infection in cystic fibrosis (CF) adults, and whether the prevalence is changing.

Methods

We employed a retrospective cohort to analyze data from a single adult CF center (2002 to 2012). Regression models were used to assess independent predictors and change in prevalence of chronic and mucoid Pa infection over time.

Results

The odds ratio of mucoid Pa infection was significantly less in individuals with better baseline lung function (OR 0.84,95%CI:0.77–0.92) and those diagnosed after the age of 25 (OR 0.21, 95%CI:0.05–0.95). The prevalence of chronic Pa and mucoid Pa decreased during the time interval. After adjusting for confounders, the observed decrease in chronic and mucoid Pa between 2002 and 2012 was no longer significant.

Conclusions

The prevalence of chronic and mucoid Pa is decreasing. Larger studies are needed to confirm these regional trends and their significance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-016-0333-y) contains supplementary material, which is available to authorized users.

Biomarkers for cystic fibrosis drug development

PURPOSE

To provide a review of the status of biomarkers in cystic fibrosis drug development, including regulatory definitions and considerations, a summary of biomarkers in current use with supportive data, current gaps, and future needs.

METHODS

Biomarkers are considered across several areas of CF drug development, including cystic fibrosis transmembrane conductance regulator modulation, infection, and inflammation.

RESULTS

Sweat chloride, nasal potential difference, and intestinal current measurements have been standardized and examined in the context of multicenter trials to quantify CFTR function. Detection and quantification of pathogenic bacteria in CF respiratory cultures (e.g.: Pseudomonas aeruginosa) are commonly used in early phase antimicrobial clinical trials, and to monitor safety of therapeutic interventions. Sputum (e.g.: neutrophil elastase, myeloperoxidase, calprotectin) and blood biomarkers (e.g.: C reactive protein, calprotectin, serum amyloid A) have had variable success in detecting response to inflammatory treatments.

CONCLUSIONS

Biomarkers are used throughout the drug development process in CF, and many have been used in early phase clinical trials to provide proof of concept, detect drug bioactivity, and inform dosing for later-phase studies. Advances in the precision of current biomarkers, and the identification of new biomarkers with 'omics-based technologies, are needed to accelerate CF drug development.

Oral anti-pseudomonal antibiotics for cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa is the most common bacterial pathogen causing lung infections in people with cystic fibrosis and appropriate antibiotic therapy is vital. Antibiotics for pulmonary exacerbations are usually given intravenously, and for long-term treatment, via a nebuliser. Oral anti-pseudomonal antibiotics with the same efficacy and safety as intravenous or nebulised antibiotics would benefit people with cystic fibrosis due to ease of treatment and avoidance of hospitalisation. This is an update of a previous review.

OBJECTIVES

To determine the benefit or harm of oral anti-pseudomonal antibiotic therapy for people with cystic fibrosis, colonised with Pseudomonas aeruginosa, in the:1. treatment of a pulmonary exacerbation; and2. long-term treatment of chronic infection.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.We contacted pharmaceutical companies and checked reference lists of identified trials.Date of last search: 08 July 2016.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials comparing any dose of oral anti-pseudomonal antibiotics, to other combinations of inhaled, oral or intravenous antibiotics, or to placebo or usual treatment for pulmonary exacerbations and long-term treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently selected the trials, extracted data and assessed quality. We contacted trial authors to obtain missing information.

MAIN RESULTS

We included three trials examining pulmonary exacerbations (171 participants) and two trials examining long-term therapy (85 participants). We regarded the most important outcomes as quality of life and lung function. The analysis did not identify any statistically significant difference between oral anti-pseudomonal antibiotics and other treatments for these outcome measures for either pulmonary exacerbations or long-term treatment. One of the included trials reported significantly better lung function when treating a pulmonary exacerbation with ciprofloxacin when compared with intravenous treatment; however, our analysis did not confirm this finding. We found no evidence of difference between oral anti-pseudomonal antibiotics and other treatments regarding adverse events or development of antibiotic resistance, but trials were not adequately powered to detect this. None of the studies had a low risk of bias from blinding which may have an impact particularly on subjective outcomes such as quality of life. The risk of bias for other criteria could not be clearly stated across the studies.

AUTHORS' CONCLUSIONS

We found no conclusive evidence that an oral anti-pseudomonal antibiotic regimen is more or less effective than an alternative treatment for either pulmonary exacerbations or long-term treatment of chronic infection with P. aeruginosa. Until results of adequately-powered future trials are available, treatment needs to be selected on a pragmatic basis, based upon any available non-randomised evidence, the clinical circumstances of the individual, the known effectiveness of drugs against local strains and upon individual preference.

Characterization of Missing Data in Clinical Registry Studies

Patterns of missing data are seldom well-characterized in observational research. This study examined the magnitude of, and factors associated with, missing data across multiple observational studies. Missingness was evaluated for demographic, clinical, and patient-reported outcome (PRO) data from a procedure registry (TOPS), a rare disease (cystic fibrosis) registry (Port-CF), and a comparative effectiveness registry (glaucoma, RiGOR). Generalized linear mixed effects models were fit to assess whether patient characteristics or follow-up methods predicted missingness. Data from 156,707 surgical procedures, 32,118 cystic fibrosis patients, and 2373 glaucoma patients were analyzed. Data were rarely missing for demographics, treatments, and outcomes. Missingness for clinical variables varied by registry and measure and depended on whether a variable was required. Within RiGOR, PRO forms were missing more often when collected by e-mail compared with office-based paper data collection. In Port-CF, missingness varied based on insurance status and sex. Strategic consideration of operational approaches affecting missing data should be performed prior to data collection and assessed periodically during study conduct.

Proximity to blue spaces and risk of infection with Pseudomonas aeruginosa in cystic fibrosis: A case-control analysis

BACKGROUND

The acquisition of Pseudomonas aeruginosa in cystic fibrosis (CF) is associated with lower survival, decreased lung function, worse radiological scores, increased exacerbations and reduced nutritional status. Open water is a known reservoir and a potential source of exposure to P. aeruginosa.

METHODS

Twenty eight adult CF patients who had no history of P. aeruginosa and had negative P. aeruginosa IgG antibody levels, were matched by age and sex with 28 CF patients with chronic P. aeruginosa colonization. Straight line and closest walking distance from patient's residence to the nearest "blue space", i.e. surface water as determined by Google Earth, were compared between the two groups, and odds ratios (OR) were estimated using conditional logistic regression.

RESULTS

Patients who were never infected with P. aeruginosa lived significantly further away from a natural water source than P. aeruginosa colonized patients, both when considering shortest walking distance (mean 487 m vs 308 m, p=0.014) and beeline (mean 324 m vs 202 m, p=0.021). Conditional logistic regression (correcting for FEV1%) revealed ORs for chronic P. aeruginosa colonization of 0.35 (95% CI 0.13-0.98; p=0.045) and 0.12 (95% CI 0.02-0.81; p=0.028) for each doubling in the beeline or walking distance, respectively, between residence and open water.

CONCLUSION

We discovered that adult CF patients without P. aeruginosa infection live significantly further from blue space than CF patients with chronic P. aeruginosa colonization. Within the limitations of a case-control study, this may indicate that natural open water represents a source of infection by P. aeruginosa in CF.

REGISTRATION

The study was approved by the local ethical committee of the UZ Leuven, Belgium (ML-5028).

Clinical applications of pulmonary delivery of antibiotics

The treatment of infection typically involves administration of antibiotics by a systemic route, such as intravenous or oral. However, pulmonary infections can also be approached by inhalation of antibiotics as the infection is more directly accessible via the airways, making inhalation delivery essentially topical administration. This approach offers deposition of high antimicrobial concentrations directly at the site of infection but with a potentially reduced systemic exposure. This review covers the evidence for aerosolized antibiotics for the treatment of a number of conditions such as cystic fibrosis (CF), where it has become the standard of care for chronic infection, as well as non-CF bronchiectasis, non-tuberculous mycobacteria, and ventilator-associated infection where such therapy does not have an approved indication but has been used with increasing frequency.

Multidimensional clinical phenotyping of an adult cystic fibrosis patient population

Background

Cystic Fibrosis (CF) is a multi-systemic disease resulting from mutations in the Cystic Fibrosis Transmembrane Regulator (CFTR) gene and has major manifestations in the sino-pulmonary, and gastro-intestinal tracts. Clinical phenotypes were generated using 26 common clinical variables to generate classes that overlapped quantiles of lung function and were based on multiple aspects of CF systemic disease.

Methods

The variables included age, gender, CFTR mutations, FEV1% predicted, FVC% predicted, height, weight, Brasfield chest xray score, pancreatic sufficiency status and clinical microbiology results. Complete datasets were compiled on 211 subjects. Phenotypes were identified using a proximity matrix generated by the unsupervised Random Forests algorithm and subsequent clustering by the Partitioning around Medoids (PAM) algorithm. The final phenotypic classes were then characterized and compared to a similar dataset obtained three years earlier.

Findings

Clinical phenotypes were identified using a clustering strategy that generated four and five phenotypes. Each strategy identified 1) a low lung health scores phenotype, 2) a younger, well-nourished, male-dominated class, 3) various high lung health score phenotypes that varied in terms of age, gender and nutritional status. This multidimensional clinical phenotyping strategy identified classes with expected microbiology results and low risk clinical phenotypes with pancreatic sufficiency.

Interpretation

This study demonstrated regional adult CF clinical phenotypes using non-parametric, continuous, ordinal and categorical data with a minimal amount of subjective data to identify clinically relevant phenotypes. These studies identified the relative stability of the phenotypes, demonstrated specific phenotypes consistent with published findings and identified others needing further study.

Pseudomonas aeruginosa in cystic fibrosis patients with G551D-CFTR treated with ivacaftor

BACKGROUND

Ivacaftor improves outcomes in cystic fibrosis (CF) patients with the G551D mutation; however, effects on respiratory microbiology are largely unknown. This study examines changes in CF respiratory pathogens with ivacaftor and correlates them with baseline characteristics and clinical response.

METHODS

The G551D Observational Study enrolled a longitudinal observational cohort of US patients with CF aged 6 years and older with at least 1 copy of the G551D mutation. Results were linked with retrospective and prospective culture data in the US Cystic Fibrosis Foundation's National Patient Registry. Pseudomonas aeruginosa infection category in the year before and year after ivacaftor was compared and correlated with clinical findings.

RESULTS

Among 151 participants prescribed ivacaftor, 29% (26/89) who were culture positive for P. aeruginosa the year prior to ivacaftor use were culture negative the year following treatment; 88% (52/59) of those P. aeruginosa free remained uninfected. The odds of P. aeruginosa positivity in the year after ivacaftor compared with the year prior were reduced by 35% (odds ratio [OR], 0.65; P < .001). Ivacaftor was also associated with reduced odds of mucoid P. aeruginosa (OR, 0.77; P = .013) and Aspergillus (OR, 0.47; P = .039), but not Staphylococcus aureus or other common CF pathogens. Patients with intermittent culture positivity and higher forced expiratory volume in 1 second (FEV1) were most likely to turn culture negative. Reduction in P. aeruginosa was not associated with change in FEV1, body mass index, or hospitalizations.

CONCLUSIONS

Pseudomonas aeruginosa culture positivity was significantly reduced following ivacaftor treatment. Efficacious CFTR modulation may contribute to lower frequency of culture positivity for P. aeruginosa and other respiratory pathogens, particularly in patients with less established disease.

Antibiotic strategies for eradicating Pseudomonas aeruginosa in people with cystic fibrosis

BACKGROUND

Respiratory tract infection with Pseudomonas aeruginosa occurs in most people with cystic fibrosis. Once chronic infection is established, Pseudomonas aeruginosa is virtually impossible to eradicate and is associated with increased mortality and morbidity. Early infection may be easier to eradicate.This is an update of a Cochrane review first published in 2003, and previously updated in 2006 and 2009.

OBJECTIVES

To determine whether antibiotic treatment of early Pseudomonas aeruginosa infection in children and adults with cystic fibrosis eradicates the organism, delays the onset of chronic infection, and results in clinical improvement. To evaluate whether there is evidence that a particular antibiotic strategy is superior to or more cost-effective than other strategies and to compare the adverse effects of different antibiotic strategies (including respiratory infection with other micro-organisms).

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Most recent search: 08 September 2014.

SELECTION CRITERIA

We included randomised controlled trials of people with cystic fibrosis, in whom Pseudomonas aeruginosa had recently been isolated from respiratory secretions. We compared combinations of inhaled, oral or intravenous antibiotics with placebo, usual treatment or other combinations of inhaled, oral or intravenous antibiotics. We excluded non-randomised trials, cross-over trials, and those utilising historical controls.

DATA COLLECTION AND ANALYSIS

Both authors independently selected trials, assessed risk of bias and extracted data.

MAIN RESULTS

The search identified 49 trials; seven trials (744 participants) with a duration between 28 days and 27 months were eligible for inclusion. Three of the trials are over 10 years old and their results may be less applicable today given the changes in standard treatment. Some of the trials had low numbers of participants and most had relatively short follow-up periods; however, there was generally a low risk of bias from missing data. In most trials it was difficult to blind participants and clinicians to treatment given the interventions and comparators used. Two trials were supported by the manufacturers of the antibiotic used.Evidence from two trials (38 participants) at the two-month time-point showed treatment of early Pseudomonas aeruginosa infection with inhaled tobramycin results in microbiological eradication of the organism from respiratory secretions more often than placebo, odds ratio 0.15 (95% confidence interval 0.03 to 0.65) and data from one of these trials, with longer follow up, suggested that this effect may persist for up to 12 months.One randomised controlled trial (26 participants) compared oral ciprofloxacin and nebulised colistin versus usual treatment. Results after two years suggested treatment of early infection results in microbiological eradication of Pseudomonas aeruginosa more often than no anti-pseudomonal treatment, odds ratio 0.12 (95% confidence interval 0.02 to 0.79).One trial comparing 28 days to 56 days treatment with nebulised tobramycin solution for inhalation in 88 participants showed that both treatments were effective and well-tolerated, with no notable additional improvement with longer over shorter duration of therapy. However, this trial was not powered to detect non-inferiority or equivalence .A trial of oral ciprofloxacin with inhaled colistin versus nebulised tobramycin solution for inhalation alone (223 participants) failed to show a difference between the two strategies, although it was underpowered to show this. A further trial of inhaled colistin with oral ciprofloxacin versus nebulised tobramycin solution for inhalation with oral ciprofloxacin also showed no superiority of the former, with increased isolation of Stenotrophomonas maltophilia in both groups.A recent, large trial in 306 children aged between one and 12 years compared cycled nebulised tobramycin solution for inhalation to culture-based therapy and also ciprofloxacin to placebo. The primary analysis showed no difference in time to pulmonary exacerbation or proportion of Pseudomonas aeruginosa positive cultures. An analysis performed in this review (not adjusted for age) showed fewer participants in the cycled therapy group with one or more isolates of Pseudomonas aeruginosa, odds ratio 0.51 (95% CI 0.31 to 0.28).

AUTHORS' CONCLUSIONS

We found that nebulised antibiotics, alone or in combination with oral antibiotics, were better than no treatment for early infection with Pseudomonas aeruginosa. Eradication may be sustained for up to two years. There is insufficient evidence to determine whether antibiotic strategies for the eradication of early Pseudomonas aeruginosa decrease mortality or morbidity, improve quality of life, or are associated with adverse effects compared to placebo or standard treatment. Four trials of two active treatments have failed to show differences in rates of eradication of Pseudomonas aeruginosa. There have been no published randomised controlled trials that investigate the efficacy of intravenous antibiotics to eradicate Pseudomonas aeruginosa in cystic fibrosis. Overall, there is still insufficient evidence from this review to state which antibiotic strategy should be used for the eradication of early Pseudomonas aeruginosa infection in cystic fibrosis.

Is infection with hypermutable Pseudomonas aeruginosa clinically significant?

BACKGROUND

Hypermutable Pseudomonas aeruginosa (HPA) with high mutation rate due to defects in the DNA mismatch repair genes are frequently isolated in the sputum of cystic fibrosis (CF) patients. These isolates tend to be multidrug resistant and may be better adapted to the CF lung environment. However, the clinical significance of this infection has not been determined.

METHODS

This prospective study enrolled patients with PA infection attending CF clinics in Jerusalem between 2010 and 2011. Mutation frequency of pseudomonas isolates was determined by quantification of colonies resistant to rifampicin.

RESULTS

Of the 73 patients enrolled, 22 (30%) were infected with HPA. Average mutation frequency was 2.95×10(-4) in HPA and 1×10(-7) in non-HPA. Pulmonary function tests, number of pulmonary exacerbations and the response to antibiotic therapy were similar between patients infected with HPA and non-HPA isolates. The only predictors for infection with HPA were resistance to multiple antimicrobial categories (OR=4.8, 95% CI: 1.8-12.4) and previous use of inhaled colistin (OR=8.1, 95% CI: 2-30). Resistant mutant subpopulation analysis was a poor screening test for identifying HPA isolates.

CONCLUSIONS

Infection with hypermutable strains represents the marked ability of PA to adapt to the lung environment, but was not associated with worse clinical outcome.

The Pseudomonas aeruginosa AlgZR two-component system coordinates multiple phenotypes

Pseudomonas aeruginosa is an opportunistic pathogen that causes a multitude of infections. These infections can occur at almost any site in the body and are usually associated with a breach of the innate immune system. One of the prominent sites where P. aeruginosa causes chronic infections is within the lungs of cystic fibrosis patients. P. aeruginosa uses two-component systems that sense environmental changes to differentially express virulence factors that cause both acute and chronic infections. The P. aeruginosa AlgZR two component system is one of its global regulatory systems that affects the organism's fitness in a broad manner. This two-component system is absolutely required for two P. aeruginosa phenotypes: twitching motility and alginate production, indicating its importance in both chronic and acute infections. Additionally, global transcriptome analyses indicate that it regulates the expression of many different genes, including those associated with quorum sensing, type IV pili, type III secretion system, anaerobic metabolism, cyanide and rhamnolipid production. This review examines the complex AlgZR regulatory network, what is known about the structure and function of each protein, and how it relates to the organism's ability to cause infections.

Release of cystic fibrosis airway inflammatory markers from Pseudomonas aeruginosa-stimulated human neutrophils involves NADPH oxidase-dependent extracellular DNA trap formation

Cystic fibrosis (CF) airways are characterized by bacterial infections, excess mucus production, and robust neutrophil recruitment. The main CF airway pathogen is Pseudomonas aeruginosa. Neutrophils are not capable of clearing the infection. Neutrophil primary granule components, myeloperoxidase (MPO) and human neutrophil elastase (HNE), are inflammatory markers in CF airways, and their increased levels are associated with poor lung function. Identifying the mechanism of MPO and HNE release from neutrophils is of high clinical relevance for CF. In this article, we show that human neutrophils release large amounts of neutrophil extracellular traps (NETs) in the presence of P. aeruginosa. Bacteria are entangled in NETs and colocalize with extracellular DNA. MPO, HNE, and citrullinated histone H4 are all associated with DNA in Pseudomonas-triggered NETs. Both laboratory standard strains and CF isolates of P. aeruginosa induce DNA, MPO, and HNE release from human neutrophils. The increase in peroxidase activity of neutrophil supernatants after Pseudomonas exposure indicates that enzymatically active MPO is released. P. aeruginosa induces a robust respiratory burst in neutrophils that is required for extracellular DNA release. Inhibition of the cytoskeleton prevents Pseudomonas-initiated superoxide production and DNA release. NADPH oxidase inhibition suppresses Pseudomonas-induced release of active MPO and HNE. Blocking MEK/ERK signaling results in only minimal inhibition of DNA release induced by Pseudomonas. Our data describe in vitro details of DNA, MPO, and HNE release from neutrophils activated by P. aeruginosa. We propose that Pseudomonas-induced NET formation is an important mechanism contributing to inflammatory conditions characteristic of CF airways.

Vaccines for Pseudomonas aeruginosa: a long and winding road

Despite the recognition of Pseudomonas aeruginosa as an opportunistic pathogen, no vaccine against this bacteria has come to market. This review describes the current state-of-the-art in vaccinology for this bacterium. This includes a discussion of those at risk for infection, the types of vaccines and the approaches for empirical and targeted antigen selection under development, as well as a perspective on where the field should go. In addition, the challenges in developing a vaccine for those individuals at risk are discussed.

The complex interplay of iron, biofilm formation, and mucoidy affecting antimicrobial resistance of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterial pathogen that is refractory to a variety of current antimicrobial therapeutic regimens. Complicating treatment for such infections is the ability of P. aeruginosa to form biofilms, as well as several innate and acquired resistance mechanisms. Previous studies suggest iron plays a role in resistance to antimicrobial therapy, including the efficacy of an FDA-approved iron chelator, deferasirox (DSX), or Gallium, an iron analog, in potentiating antibiotic-dependent killing of P. aeruginosa biofilms. Here, we show that iron-replete conditions enhance resistance of P. aeruginosa nonbiofilm growth against tobramycin and tigecycline. Interestingly, the mechanism of iron-enhanced resistance to each of these antibiotics is distinct. Whereas pyoverdine-mediated iron uptake is important for optimal resistance to tigecycline, it does not enhance tobramycin resistance. In contrast, heme supplementation results in increased tobramycin resistance, while having no significant effect on tigecycline resistance. Thus, nonsiderophore bound iron plays an important role in resistance to tobramycin, while pyoverdine increases the ability of P. aeruginosa to resist tigecycline treatment. Lastly, we show that iron increases the minimal concentration of tobramycin, but not tigecycline, required to eradicate P. aeruginosa biofilms. Moreover, iron depletion blocks the previous observed induction of biofilm formation by subinhibitory concentrations of tobramycin, suggesting iron and tobramycin signal through overlapping regulatory pathways to affect biofilm formation. These data further support the role of iron in P. aeruginosa antibiotic resistance, providing yet another compelling case for targeting iron acquisition for future antimicrobial drug development.

Oral anti-pseudomonal antibiotics for cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa is the most common bacterial pathogen causing lung infections in people with CF and appropriate antibiotic therapy is vital. Antibiotics for pulmonary exacerbations are usually given intravenously, and for long-term treatment, via a nebuliser. Oral anti-pseudomonal antibiotics with the same efficacy and safety as intravenous or nebulised antibiotics would benefit people with CF due to ease of treatment and avoidance of hospitalisation.

OBJECTIVES

To determine the benefit or harm of oral anti-pseudomonal antibiotic therapy for people with CF, colonised with Pseudomonas aeruginosa, in the:1. treatment of a pulmonary exacerbation; and 2. long-term treatment of chronic infection.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.We contacted pharmaceutical companies and checked reference lists of identified trials.Date of last search: 28 June 2013.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials comparing any dose of oral anti-pseudomonal antibiotics, to other combinations of inhaled, oral or intravenous antibiotics, or to placebo or usual treatment for pulmonary exacerbations and long-term treatment.

DATA COLLECTION AND ANALYSIS

Two authors independently selected the trials, extracted data and assessed quality. We contacted trial authors to obtain missing information.

MAIN RESULTS

We included three trials examining pulmonary exacerbations (171 participants) and two trials examining long-term therapy (85 participants). We regarded the most important outcomes as quality of life and lung function. The analysis did not identify any statistically significant difference between oral anti-pseudomonal antibiotics and other treatments for these outcome measures for either pulmonary exacerbations or long-term treatment. One of the included trials reported significantly better lung function when treating a pulmonary exacerbation with ciprofloxacin when compared with intravenous treatment; however, our analysis did not confirm this finding. We found no evidence of difference between oral anti-pseudomonal antibiotics and other treatments regarding adverse events or development of antibiotic resistance, but trials were not adequately powered to detect this. None of the studies had a low risk of bias from blinding which may have an impact particularly on subjective outcomes such as quality of life. The risk of bias for other criteria could not be clearly stated across the studies.

AUTHORS' CONCLUSIONS

We found no conclusive evidence that an oral anti-pseudomonal antibiotic regimen is more or less effective than an alternative treatment for either pulmonary exacerbations or long-term treatment of chronic infection with P. aeruginosa. Until results of adequately-powered future trials are available, treatment needs to be selected on a pragmatic basis, based upon any available non-RCT evidence, the clinical circumstances of the individual, the known effectiveness of drugs against local strains and upon individual preference.

Clearance of initial mucoid Pseudomonas aeruginosa in patients with cystic fibrosis

BACKGROUND

Accelerated lung function decline in cystic fibrosis (CF) is associated with mucoid Pseudomonas aeruginosa infection. Recent data suggest that mucoid P. aeruginosa may amenable to elimination from the airway. We aim to determine whether the initiation of an aggressive antibiotic eradication regimen upon initial discovery of mucoid P. aeruginosa in the CF airway could be successful in clearing the organism from the CF lung.

METHODS

We performed a retrospective analysis of patients with CF who demonstrated new growth of mucoid P. aeruginosa in an airway culture between January 2003 and December 2008. The primary endpoint was clearance of mucoid P. aeruginosa, based upon the Leeds criteria, with no further growth of mucoid P. aeruginosa cultures within 12 months of the initial discovery and treatment. Factors associated with successful clearance were also evaluated.

RESULTS

Forty-eight of 355 patients with CF had a new diagnosis of mucoid P. aeruginosa during the study period; 15 patients underwent an eradication attempt, while 33 patients received no increase in therapy. We observed clearance of mucoid P. aeruginosa in 73.3% of patients undergoing an eradication attempt, whereas 36.6% of those that did not undergo attempted eradication cleared the organism at 1 year (P < 0.05). Prolonged mucoid P. aeruginosa airway clearance (>24 months) for mucoid P. aeruginosa was seen in 60.0% in subjects undergoing eradication compared to 21.2% (P = 0.02) in control patients. At the study conclusion, lung function was greater in subjects who underwent an eradication attempt than in patients who did not undergo an eradication attempt (FEV(1) %: 91.7% vs. 75.0%, P = 0.04).

CONCLUSIONS

Clearance of initial mucoid P. aeruginosa from the airways of select patients with CF is possible with current antibiotic regimens, and the attempt may be associated with improved lung function.

Surfactant protein A blocks recognition of Pseudomonas aeruginosa by CKAP4/P63 on airway epithelial cells

We used isogenic mutant strains that were deficient or over-expressed capsule to study the function of the alginate exopolysaccharide in the interaction of Pseudomonas aeruginosa with the human airway epithelial cells (AEC) in the presence or absence of surfactant protein A (SP-A). SP-A prevented the invasion of AEC by alginate-producing P. aeruginosa strains because of a direct effect on the AEC. Monoclonal antibodies to CKAP4/P63, the principal SP-A-binding receptor on AEC, or inhibition of its expression using specific siRNA reduced the invasion of both highly encapsulated and poorly encapsulated strains, but not the invasion of the acapsular mutant. Treatment of AEC with SP-A, monoclonal antibodies to CKAP4/P63, or CKAP4/P63-specific siRNA decreased the binding of purified alginate exopolysaccharide to AEC. Alginate binding to AEC reduced SP-A release by these cells. Because the alginate exopolysaccharide is surface-exposed, levels of SP-A may be crucial to modulate the interaction of P. aeruginosa with AEC.

Future directions in early cystic fibrosis lung disease research: an NHLBI workshop report

Since the 1989 discovery that mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause cystic fibrosis (CF), there has been substantial progress toward understanding the molecular basis for CF lung disease, leading to the discovery and development of new therapeutic approaches. However, the earliest impact of the loss of CFTR function on airway physiology and structure and its relationship to initial infection and inflammation are poorly understood. Universal newborn screening for CF in the United States represents an unprecedented opportunity for investigating CF clinical manifestations very early in life. Recently developed animal models with pulmonary phenotypic manifestations also provide a window into the early consequences of this genetic disorder. For these reasons, the National Heart, Lung, and Blood Institute (NHLBI) convened a working group of extramural experts, entitled "Future Research Directions in Early CF Lung Disease" on September 21-22, 2010, to identify future research directions of great promise in CF. The priority areas identified included (1) exploring pathogenic mechanisms of early CF lung disease; (2) leveraging newborn screening to elucidate the natural history of early lung disease; (3) developing a spectrum of biomarkers of early lung disease that reflects CF pathophysiology, clinical outcome, and response to treatment; (4) exploring the role of genetics/genomics (e.g., modifier genes, gene-environmental interactions, and epigenetics) in early CF pathogenesis; (5) defining early microbiological events in CF lung disease; and (6) elucidating the initial airway inflammatory, remodeling, and repair mechanisms in CF lung disease.

Cystic fibrosis mutations for p.F508del compound heterozygotes predict sweat chloride levels and pancreatic sufficiency

Cystic fibrosis (CF) is a monogenetic disease with a complex phenotype. Over 1500 mutations in the CFTR gene have been identified; however, the p.F508del mutation is most common. There has been limited correlation between the CFTR mutation genotype and the disease phenotypes. We evaluated the non-p.F508del mutation of 108 p.F508del compound heterozygotes using the biological classification method, Grantham and Sorting Intolerant from Tolerant (SIFT) scores to assess whether these scoring systems correlated with sweat chloride levels, pancreatic sufficiency, predicted FEV(1) , and risk of infection with Pseudomonas aeruginosa in the last year. Mutations predicted to be 'mild' by the biological classification method are associated with more normal sweat chloride levels (p < 0.001), pancreatic sufficiency (p < 0.001) and decreased risk of infection with Pseudomonas in the last year (p = 0.014). Lower Grantham scores are associated with more normal sweat chloride levels (p < 0.001), and pancreatic sufficiency (p = 0.014). Higher SIFT scores are associated with more normal sweat chloride levels (p < 0.001) and pancreatic sufficiency (p = 0.011). There was no association between pulmonary function measured by predicted FEV(1) and the biological classification (p = 0.98), Grantham (p = 0.28) or SIFT scores (p = 0.62), which suggests the pulmonary disease related to CF may involve other modifier genes and environmental factors.

Functional characterization of pfm in protein secretion and lung infection of Pseudomonas aeruginosa

Lung infections caused by Pseudomonas aeruginosa in cystic fibrosis (CF) patients cause progressive airway obstruction and tissue damage, which is the predominant cause of morbidity and mortality in patients with CF. This paper describes the functional characterization of the pfm gene (open reading frame PA2950) of P. aeruginosa. Using DNA microarrays, we found that the transcriptional levels of type II secretory system genes were significantly reduced in the pfm mutant strain. The type-II-dependent exoprotein LasB could not be secreted normally. The pfm gene was identified as a gene involved in bacterial protein secretion that was critical for the extracellular release of elastase in P. aeruginosa. The abilities to induce lung injury by wild-type and pfm mutant P. aeruginosa were evaluated in a murine acute lung infection model. The results showed that the pathogenicity and virulence of the pfm mutant strain was significantly reduced compared with that of the wild-type strain. The pfm gene and its expression product, as potential new drug targets against P. aeruginosa infection, have important research significance.

Neutrophil extracellular trap (NET)-mediated killing of Pseudomonas aeruginosa: evidence of acquired resistance within the CF airway, independent of CFTR

The inability of neutrophils to eradicate Pseudomonas aeruginosa within the cystic fibrosis (CF) airway eventually results in chronic infection by the bacteria in nearly 80 percent of patients. Phagocytic killing of P. aeruginosa by CF neutrophils is impaired due to decreased cystic fibrosis transmembrane conductance regulator (CFTR) function and virulence factors acquired by the bacteria. Recently, neutrophil extracellular traps (NETs), extracellular structures composed of neutrophil chromatin complexed with granule contents, were identified as an alternative mechanism of pathogen killing. The hypothesis that NET-mediated killing of P. aeruginosa is impaired in the context of the CF airway was tested. P. aeruginosa induced NET formation by neutrophils from healthy donors in a bacterial density dependent fashion. When maintained in suspension through continuous rotation, P. aeruginosa became physically associated with NETs. Under these conditions, NETs were the predominant mechanism of killing, across a wide range of bacterial densities. Peripheral blood neutrophils isolated from CF patients demonstrated no impairment in NET formation or function against P. aeruginosa. However, isogenic clinical isolates of P. aeruginosa obtained from CF patients early and later in the course of infection demonstrated an acquired capacity to withstand NET-mediated killing in 8 of 9 isolates tested. This resistance correlated with development of the mucoid phenotype, but was not a direct result of the excess alginate production that is characteristic of mucoidy. Together, these results demonstrate that neutrophils can kill P. aeruginosa via NETs, and in vitro this response is most effective under non-stationary conditions with a low ratio of bacteria to neutrophils. NET-mediated killing is independent of CFTR function or bacterial opsonization. Failure of this response in the context of the CF airway may occur, in part, due to an acquired resistance against NET-mediated killing by CF strains of P. aeruginosa.

Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis

OBJECTIVE

To investigate the efficacy and safety of 4 antipseudomonal treatments in children with cystic fibrosis with recently acquired Pseudomonas aeruginosa infection.

DESIGN

Randomized controlled trial.

SETTING

Multicenter trial in the United States.

PARTICIPANTS

Three hundred four children with cystic fibrosis aged 1 to 12 years within 6 months of P aeruginosa detection.

INTERVENTIONS

Participants were randomized to 1 of 4 antibiotic regimens for 18 months (six 12-week quarters) between December 2004 and June 2009. Participants randomized to cycled therapy received tobramycin inhalation solution (300 mg twice a day) for 28 days, with oral ciprofloxacin (15-20 mg/kg twice a day) or oral placebo for 14 days every quarter, while participants randomized to culture-based therapy received the same treatments only during quarters with positive P aeruginosa cultures.

MAIN OUTCOME MEASURES

The primary end points were time to pulmonary exacerbation requiring intravenous antibiotics and proportion of P aeruginosa -positive cultures.

RESULTS

The intention-to-treat analysis included 304 participants. There was no interaction between treatments. There were no statistically significant differences in exacerbation rates between cycled and culture-based groups (hazard ratio, 0.95; 95% confidence interval [CI], 0.54-1.66) or ciprofloxacin and placebo (hazard ratio, 1.45; 95% CI, 0.82-2.54). The odds ratios of P aeruginosa- positive culture comparing the cycled vs culture-based group were 0.78 (95% CI, 0.49-1.23) and 1.10 (95% CI, 0.71-1.71) comparing ciprofloxacin vs placebo. Adverse events were similar across groups.

CONCLUSIONS

No difference in the rate of exacerbation or prevalence of P aeruginosa positivity was detected between cycled and culture-based therapies. Adding ciprofloxacin produced no benefits.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00097773.

Evolution and diversification of Pseudomonas aeruginosa in the paranasal sinuses of cystic fibrosis children have implications for chronic lung infection

The opportunistic pathogen Pseudomonas aeruginosa is a frequent colonizer of the airways of patients suffering from cystic fibrosis (CF). Depending on early treatment regimens, the colonization will, with high probability, develop into chronic infections sooner or later, and it is important to establish under which conditions the switch to chronic infection takes place. In association with a recently established sinus surgery treatment program for CF patients at the Copenhagen CF Center, colonization of the paranasal sinuses with P. aeruginosa has been investigated, paralleled by sampling of sputum from the same patients. On the basis of genotyping and phenotypic characterization including transcription profiling, the diversity of the P. aeruginosa populations in the sinuses and the lower airways was investigated and compared. The observations made from several children show that the paranasal sinuses constitute an important niche for the colonizing bacteria in many patients. The paranasal sinuses often harbor distinct bacterial subpopulations, and in the early colonization phases there seems to be a migration from the sinuses to the lower airways, suggesting that independent adaptation and evolution take place in the sinuses. Importantly, before the onset of chronic lung infection, lineages with mutations conferring a large fitness benefit in CF airways such as mucA and lasR as well as small colony variants and antibiotic-resistant clones are part of the sinus populations. Thus, the paranasal sinuses potentially constitute a protected niche of adapted clones of P. aeruginosa, which can intermittently seed the lungs and pave the way for subsequent chronic lung infections.

Efficacy of a conjugate vaccine containing polymannuronic acid and flagellin against experimental Pseudomonas aeruginosa lung infection in mice

Vaccines that could effectively prevent Pseudomonas aeruginosa pulmonary infections in the settings of cystic fibrosis (CF) and nosocomial pneumonia could be exceedingly useful, but to date no effective immunotherapy targeting this pathogen has been successfully developed for routine use in humans. Evaluations using animals and limited human trials of vaccines and their associated immune effectors against different P. aeruginosa antigens have suggested that antibody to the conserved surface polysaccharide alginate, as well as the flagellar proteins, often give high levels of protection. However, alginate itself does not elicit protective antibody in humans, and flagellar vaccines containing the two predominant serotypes of this antigen may not provide sufficient coverage against variant flagellar types. To evaluate if combining these antigens in a conjugate vaccine would be potentially efficacious, we conjugated polymannuronic acid (PMA), containing the blocks of mannuronic acid conserved in all P. aeruginosa alginates, to type a flagellin (FLA) and evaluated immunogenicity, opsonic killing activity, and passive protective efficacy in mice. The PMA-FLA conjugate was highly immunogenic in mice and rabbits and elicited opsonic antibodies against mucoid but not nonmucoid P. aeruginosa, but nonetheless rabbit antibody to PMA-FLA showed evidence of protective efficacy against both types of this organism in a mouse lung infection model. Importantly, the PMA-FLA conjugate vaccine did not elicit antibodies that neutralized the Toll-like receptor 5 (TLR5)-activating activity of flagellin, an important part of innate immunity to flagellated microbial pathogens. Conjugation of PMA to FLA appears to be a promising path for developing a broadly protective vaccine against P. aeruginosa.

Clinical significance of microbial infection and adaptation in cystic fibrosis

A select group of microorganisms inhabit the airways of individuals with cystic fibrosis. Once established within the pulmonary environment in these patients, many of these microbes adapt by altering aspects of their structure and physiology. Some of these microbes and adaptations are associated with more rapid deterioration in lung function and overall clinical status, whereas others appear to have little effect. Here we review current evidence supporting or refuting a role for the different microbes and their adaptations in contributing to poor clinical outcomes in cystic fibrosis.

Early eradication of Pseudomonas aeruginosa in patients with cystic fibrosis

Pseudomonas aeruginosa (Pa) is the predominant organism infecting the airways of patients with cystic fibrosis (CF). This organism has an armamentarium of survival mechanisms that allows it to survive in the CF airway. Since colonization and chronic infection with Pa is associated with poorer lung function and increased morbidity and mortality, therapies that can prevent infection could significantly improve the lives of patients with CF. Numerous studies have examined the effects of treatment on the eradication of Pa as a means to ameliorate disease. This article outlines the pathophysiology and clinical implication of Pa acquisition, and reviews the existing treatment regimens aimed at early eradication of Pa in patients with CF.

Anti-biofilm and resistance suppression activities of CXA-101 against chronic respiratory infection phenotypes of Pseudomonas aeruginosa strain PAO1

OBJECTIVES

Biofilm growth, mucoid phenotype and proficient resistance development by hypermutable strains dramatically limit the efficacy of current therapies for Pseudomonas aeruginosa chronic respiratory infection (CRI) in cystic fibrosis (CF) patients. We evaluated the activity of the new cephalosporin CXA-101, ceftazidime, meropenem and ciprofloxacin against biofilms of wild-type PAO1 and its mucoid (mucA), hypermutable (mutS) and mucoid-hypermutable derivatives, and analysed the capacity of these strains to develop resistance during planktonic and biofilm growth.

METHODS

MICs and MBCs were determined by microdilution, and mutant frequencies were determined at 4x and 16x the MICs. Biofilms were formed using a modified Calgary device and were incubated for 24 h with 0x, 1x, 4x or 16x the MIC of each antibiotic. Biofilms were plated, and total cells and resistant mutants enumerated.

RESULTS

CXA-101 showed concentration-independent biofilm bactericidal activity, being the most potent agent tested at 1x the MIC for wild-type, mucoid and hypermutable strains. The spontaneous mutant frequencies for CXA-101 were extremely low (<5 x 10(-11)), even for the hypermutable strain at low concentrations (4x the MIC), in sharp contrast to the other antipseudomonal agents. Accordingly, mutants resistant to 4x the MIC of CXA-101 did not emerge in biofilms for any of the strains/concentrations tested.

CONCLUSION

These data strongly suggest that resistance to CXA-101 (at least 4x the MIC) cannot be driven by single-step mutations, either in planktonic or in biofilm growth. CXA-101 shows encouraging properties for the treatment of CRI by P. aeruginosa, which need to be further evaluated in animal models and pertinent clinical trials.

Factors associated with mucoid transition of Pseudomonas aeruginosa in cystic fibrosis patients

Although the mucoid form of Pseudomonas aeruginosa (Pa) is largely responsible for the progression of lung disease in cystic fibrosis (CF), the relationship between factors relating daily-care regimes to mucoidy acquisition are as yet poorly investigated. Fifty-two CF patients registered at the CF centre of Dijon, France, were retrospectively evaluated from the date of Pa colonization either to the first positive sputum culture for mucoid Pa (n = 26) or to the last culture in which the Pa remained non-mucoid (n = 26). All clinical, pathological and therapeutic events were recorded. The association between the parameters collected and mucoid transition of Pa was assessed in a Cox model with time-dependant covariables. The mean follow-up was 4.7 + or - 4.3 years. Three independent parameters were associated with the higher risk of mucoid transition of Pa: persistence of Pa in sputum (OR 7.89; p <0.01), use of inhaled bronchodilators (OR 3.40; p = 0.04), and the use of inhaled colimycin (OR 4.04; p = 0.02). Isolation of Staphylococcus aureus, Haemophilus influenzae or Streptococcus pneumoniae in sputum was associated with a lower risk (OR 0.24; p < 0.01). Mucoid transition of Pa was associated with variables that reflected the severity of both lung disease and Pa colonization. Although they do not lead to prophylactic measures, these results corroborate the need to avoid Pa persistence.

Antibiotic strategies for eradicating Pseudomonas aeruginosa in people with cystic fibrosis

BACKGROUND

Lower respiratory tract infection with Pseudomonas aeruginosa occurs in most people with cystic fibrosis (CF). Once chronic infection is established, Pseudomonas aeruginosa is virtually impossible to eradicate and is associated with increased mortality and morbidity. Early infection may be easier to eradicate.

OBJECTIVES

To determine whether antibiotic treatment of early Pseudomonas aeruginosa infection in children and adults with CF eradicates the organism, improves clinical and microbiological outcome and is superior to or more cost-effective than other strategies.

SEARCH STRATEGY

We searched the Cochrane CF and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Most recent search: 11 December 2008.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of people with CF, in whom Pseudomonas aeruginosa had recently been isolated from respiratory secretions. We compared combinations of inhaled, oral or intravenous antibiotics with placebo, usual treatment or other combinations of inhaled, oral or intravenous antibiotics. We excluded non-randomised trials, cross-over trials, and those utilising historical controls.

DATA COLLECTION AND ANALYSIS

Both authors independently selected trials, assessed methodological quality and extracted data.

MAIN RESULTS

The search identified 25 trials. Four trials (95 participants) were eligible for inclusion; two trials are ongoing. Evidence from two trials showed treatment of early Pseudomonas aeruginosa infection with inhaled tobramycin results in microbiological eradication of the organism from respiratory secretions more often than placebo, OR 0.15 (95% CI 0.03 to 0.65) and that this effect may persist for up to 12 months. These trials were of low methodological quality.The only identified RCT of oral ciprofloxacin and nebulised colistin versus usual treatment was of poor methodological quality. Results suggested treatment of early infection results in microbiological eradication of Pseudomonas aeruginosa more often than usual treatment, after two years, OR 0.24 (95% CI 0.06 to 0.96). There is insufficient evidence to determine whether antibiotic strategies for the eradication of early Pseudomonas aeruginosa decrease mortality or morbidity, improve quality of life, or are associated with adverse effects compared to placebo or standard treatment.

AUTHORS' CONCLUSIONS

We found that nebulised antibiotics, alone or in combination with oral antibiotics, were better than no treatment for early infection with Pseudomonas aeruginosa. Eradication may be sustained in the short term. Overall, there is insufficient evidence from this review to state which antibiotic strategy should be used for the eradication of early Pseudomonas aeruginosa infection in CF.