Dynamics of long-term colonization of respiratory tract by Haemophilus influenzae in cystic fibrosis patients shows a marked increase in hypermutable strains.
The persistence and variability of 188 Haemophilus influenzae isolates in respiratory tract of 30 cystic fibrosis (CF) patients over the course of 7 years was studied. Antibiotic susceptibility testing, DNA fingerprinting, and analysis of outer membrane protein profiles were performed on all isolates. A total of 115 distinct pulsed-field gel electrophoresis profiles were identified. Ninety percent of patients were cocolonized with two or more clones over the studied period. A third of the patients were cross-colonized with one or two H. influenzae strains; 11% of the clones persisted for 3 or more months. Biotype, outer membrane protein profiles, and resistance profiles showed variation along the studied period, even in persisting clones. Four isolates (2.1%) recovered from 3 patients were type f capsulate, with three of them belonging to the same clone. beta-Lactamase production was detected in 23.9% of isolates while 7% of the beta-lactamase-negative isolates presented diminished susceptibility to ampicillin (beta-lactamase-negative ampicillin resistance phenotype). Remarkably, 21.3% of the H. influenzae isolates presented decreased susceptibility to ciprofloxacin, which was mainly observed in persisting clones. Of the H. influenzae isolates from CF patients, 18 (14.5%) were found to be hypermutable in comparison with 1 (1.4%) from non-CF patients (P < 0.0001). Ten patients (33.3%) were colonized by hypermutable strains over the study period. A multiresistance phenotype and long-term clonal persistence were significantly associated in some cases for up to 7 years. These results suggest that H. influenzae bronchial colonization in CF patients is a dynamic process, but better-adapted clones can persist for long periods of time.
Román
Federico
F
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda. Department of Microbiology, Hospital Universitario Ramón y Cajal, Madrid, Spain.
Cantón
Rafael
R
Pérez-Vázquez
María
M
Baquero
Fernando
F
Campos
José
J
D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006192:Haemophilus Infections / Q000382:microbiology; D006193:Haemophilus influenzae / Q000145:classification* / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D009154:Mutation; D012137:Respiratory System / Q000382:microbiology*
D000900:Anti-Bacterial Agents