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Journal of Clinical Microbiology, May 2005, p. 2207-2214, Vol. 43, No. 5
0095-1137/05/$08.00+0     doi:10.1128/JCM.43.5.2207-2214.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Population Structure, Antimicrobial Resistance, and Mutation Frequencies of Streptococcus pneumoniae Isolates from Cystic Fibrosis Patients

Servicio de Microbiología y Unidad de Fibrosis Quística, Hospital Universitario Ramón y Cajal, Madrid,¹ Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda,² Servicio de Microbiología, Hospital Sant Joan de Dèu, Barcelona, Spain³

Received 9 September 2004/ Returned for modification 23 November 2004/ Accepted 17 December 2004

Forty-eight Streptococcus pneumoniae isolates recovered from sputum samples from 26 cystic fibrosis (CF) patients attending our CF unit (1995 to 2003) were studied. Mean yearly incidence of isolation was 5.5%, and all were strains recovered from young patients (12 years). The isolation was linked to clinical exacerbation in 35% of the cases, but only 27% of these were not accompanied by other CF pathogens. Fifty percent of the patients presented with two to four isolates over the studied period. Pulsed-field gel electrophoresis-SmaI digestion revealed a high heterogeneity (32 pulsotypes among 48 isolates) and the persistence over a 6-month period of a single clone (clone A) in two patients. This clone, presenting a varied multiresistance phenotype, was identified as the Spain^23F-1 clone and was also recognized in six other patients, including two out of nine patients from the CF unit of Sant Joan de Dèu Hospital, Barcelona, Spain. In our isolates, 16 different serotypes were recognized, the most frequent being 23F (33.3%), 19F (18.8%), 6A (6.2%), and 6B (6.2%). High overall resistance rates were observed: to penicillin, 73%; to cefotaxime, 33%; to erythromycin, 42%; to tetracycline, 58%; to chloramphenicol, 48%; and to trimethoprim-sulfamethoxazole, 67%. Resistance to fluoroquinolones was not detected. Multiresistance was a common feature (60%). The percentage of S. pneumoniae strains with increased frequencies of mutation to rifampin resistance (7.5 x 10^–8) was significantly higher (P = 0.02) in CF (60%) than among non-CF (37%) isolates in the same institution (M. I. Morosini et al., Antimicrob. Agents Chemother. 47:1464-1467, 2003). Even though a clear association with acute exacerbations could not be observed, long-term clonal persistence and variability, high frequency of antibiotic resistance, and hypermutability indicate the plasticity for adaptation of S. pneumoniae to the CF lung environment.

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