The structure and dynamics of bacterial communities in the airways of persons with cystic fibrosis (CF) remain largely unknown. We characterized the bacterial communities in 126 sputum samples representing serial collections spanning 8-9 y from six age-matched male CF patients. Sputum DNA was analyzed by bar-coded pyrosequencing of the V3-V5 hypervariable region of the 16S rRNA gene, defining 662 operational taxonomic units (OTUs) from >633,000 sequences. Bacterial community diversity decreased significantly over time in patients with typically progressive lung disease but remained relatively stable in patients with a mild lung disease phenotype. Antibiotic use, rather than patient age or lung function, was the primary driver of decreasing diversity. Interpatient variability in community structure exceeded intrapatient variability in serial samples. Antibiotic treatment was associated with pronounced shifts in community structure, but communities showed both short-and longterm resilience after antibiotic perturbation. There was a positive correlation between OTU occurrence and relative abundance, with a small number of persistent OTUs accounting for the greatest abundance. Significant changes in community structure, diversity, or total bacterial density at the time of pulmonary exacerbation were not observed. Despite decreasing community diversity in patients with progressive disease, total bacterial density remained relatively stable over time. These findings show the critical relationship between airway bacterial community structure, disease stage, and clinical state at the time of sample collection. These features are the key parameters with which to assess the complex ecology of the CF airway. microbial ecology | microbiome | antibiotics

Rationale: In persons with cystic fibrosis (CF), repeated exacerbations of pulmonary symptoms are associated with a progressive decline in lung function. Changes in the airway microbiota around the time of exacerbations are not well understood.Objectives: To characterize changes in airway bacterial communities around the time of exacerbations and to identify predictors for these changes.Methods: DNA prepared from 68 paired baseline and exacerbation sputum samples collected from 28 patients with CF were subjected to barcoded 16S rRNA gene pyrosequencing. Bacterial density was calculated by quantitative PCR. Measurements and Main Results:Overall, significant differences in bacterial community diversity and bacterial density between baseline and exacerbation samples were not observed. However, considerable changes in community structures were observed in a subset of patients. In these patients, the dominant taxa and initial level of community diversity were significant predictors of the magnitude of community structure changes at exacerbation. Pseudomonas-dominant communities became more diverse at exacerbation compared with communities with other or no dominant species. The relative abundance of Gemella increased in 24 (83%) of 29 samples at exacerbation and was found to be the most discriminative genus between baseline and exacerbation samples. Conclusions:The magnitude of changes in the CF lung microbiota around the time of exacerbation was found to be largely dependent on community diversity and composition at baseline. Certain genera appear to play important roles in driving change in airway bacterial community composition at exacerbation. Gemella might play a direct role in and/or be a biomarker for pulmonary exacerbation.

The therapeutic potential of bacteriophage (phage) in a mouse model of acute B. cenocepacia pulmonary infection was assessed. Phage were administered by either intranasal (i.n.) inhalation or intraperitoneal (i.p.) injection. Bacterial density, macrophage inflammatory protein-2 (MIP-2), and tumor necrosis factor-α (TNFα) levels were significantly reduced in lungs of mice treated with i.p. phage. No significant differences in lung bacterial density or MIP-2 levels were found between untreated mice and mice treated with i.n. phage, i.p. UV-inactivated phage, or i.p. λ phage controls. Mock-infected mice treated with phage showed no significant increase in lung MIP-2 or TNFα levels compared to mock-infected / mock-treated mice. We have demonstrated the efficacy of phage therapy in an acute B. cenocepacia lung infection model. Systemic administration of phage was more effective than inhalational administration, suggesting that circulating phage have better access to bacteria in lung compared to topical phage.

BackgroundRecent work indicates that the airways of persons with cystic fibrosis (CF) typically harbor complex bacterial communities. However, the day-to-day stability of these communities is unknown. Further, airway community dynamics during the days corresponding to the onset of symptoms of respiratory exacerbation have not been studied.ResultsUsing 16S rRNA amplicon sequencing of 95 daily sputum specimens collected from four adults with CF, we observed varying degrees of day-to-day stability in airway bacterial community structures during periods of clinical stability. Differences were observed between study subjects with respect to the degree of community changes at the onset of exacerbation. Decreases in the relative abundance of dominant taxa were observed in three subjects at exacerbation. We observed no relationship between total bacterial load and clinical status and detected no viruses by multiplex PCR.ConclusionCF airway microbial communities are relatively stable during periods of clinical stability. Changes in microbial community structure are associated with some, but not all, pulmonary exacerbations, supporting previous observations suggesting that distinct types of exacerbations occur in CF. Decreased abundance of species that are dominant at baseline suggests a role for less abundant taxa in some exacerbations. Daily sampling revealed patterns of change in microbial community structures that may prove useful in the prediction and management of CF pulmonary exacerbations.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-015-0074-9) contains supplementary material, which is available to authorized users.

Bacteria that infect the airways of persons with cystic fibrosis (CF) include a group of well-described opportunistic pathogens as well as numerous, mainly obligate or facultative anaerobic species typically not reported by standard sputum culture. We sequenced the V3-V5 hypervariable region of the bacterial 16S rRNA gene in DNA derived from 631 sputum specimens collected from 111 CF patients over 10 years. We describe fluctuations in the relative abundances of typical CF pathogens, as well as anaerobic species, in relation to changes in patients’ clinical state and lung disease stage. Both bacterial community diversity and the relative abundance of anaerobes increased during exacerbation of symptoms (prior to antibiotic treatment), although this trend was not observed uniformly across disease stages. Community diversity and the relative abundance of anaerobic species decreased during antibiotic treatment. These results support current hypotheses regarding the role of anaerobes in CF pulmonary exacerbations and lung disease progression.