PURPOSE: Patients with cystic fibrosis (CF) are susceptible to respiratory exacerbations secondary to bacterial infections. Due to the delay in obtaining a culture result during an exacerbation, clinicians rely upon previous sputum microbiology to direct initial antibiotic selection. However, clinical experience and evidence suggest that a CF patient’s sputum microbiology does not remain static. It is unclear how well previous culture results correlate with those during an active exacerbation.
METHODS: A retrospective chart review was performed on patients with CF followed by respirologists at Royal University Hospital and treated for an exacerbation of their disease between January 1, 2005 and February 11, 2011. Patients were excluded if they had a history of lung transplantation or if sputum culture results from the current exacerbation were already available at the time of presentation.
RESULTS: 62 patient charts were reviewed. 99 exacerbations from 32 patients satisfied all inclusion and exclusion criteria. 53% of the 32 subjects were female, mean age at the time of exacerbation was 28.9 years, and mean FEV1 was 49% predicted. 19% of sputum cultures from an exacerbation yielded an organism not present on the previous sputum culture; 26% of these (5% overall) were predominating organisms. Of the 62 exacerbations for which a predominating organism was isolated from sputum, 44% of previous cultures correctly predicted the pathogen’s identity.
CONCLUSIONS: Previous and current exacerbation sputum cultures isolated similar organisms in the majority of cases. However, the predominating organisms from previous sputum cultures do not correlate well with those obtained from a current exacerbation.
CLINICAL IMPLICATIONS: The clinical strategy of using previous sputum microbiology to direct initial antibiotic selection in CF exacerbations is reasonable, as the culture results can help predict the bacteria involved. Our findings confirm that sputum culture from a current exacerbation is also required to identify the predominating organism(s) and to further guide therapy.
DISCLOSURE: Donald Cockcroft: Grant monies (from sources other than industry): AllerGen NCE ($70,000), Grant monies (from industry related sources): Asthmacure ($30,000), Grant monies (from industry related sources): Genentech ($130,000), Grant monies (from industry related sources): Astra Zeneca ($150,000), Consultant fee, speaker bureau, advisory committee, etc.: Methapharm
The following authors have nothing to disclose: Julian Tam, John Gjevre, Stephen Sanche
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