Impact of antibiotic treatment for pulmonary exacerbations on bacterial diversity in cystic fibrosis

Background: A diverse array of bacterial species is present in the CF airways, in addition to those recognised as clinically important. Here, we investigated the relative impact of antibiotics, used predominantly to target Pseudomonas aeruginosa during acute exacerbations, on other non-pseudomonal species. Methods: The relative abundance of viable P. aeruginosa and non-pseudomonal species was determined in sputa from 12 adult CF subjects 21, 14, and 7 days prior to antibiotics, day 3 of treatment, the final day of treatment, and 10–14 days afterwards, by T-RFLP profiling. Results: Overall, relative P. aeruginosa abundance increased during antibiotic therapy compared to other bacterial species; mean abundance pre-antibiotic 51.0 ± 36.0% increasing to 71.3 ± 30.4% during antibiotic (ANOVA: F1,54 = 5.16; P < 0.027). Further, the number of non-pseudomonal species detected fell; pre-antibiotic 6.0 ± 3.3 decreasing to 3.7 ± 3.3 during treatment (ANOVA: F1,66 = 5.11; P < 0.027). Conclusions: Antibiotic treatment directed at P. aeruginosa has an additional significant impact on non-pseudomonal, co-colonising species.