M038: QUINOLONE RESISTANCE IN Haemophilus influenzae ISOLATES
FROM CYSTIC FIBROSIS PATIENTS.
R. Cantón1, M.E. Alvarez1, M. Alvarez1 H. Escobar2,
L. Suarez2, B. Sánchez del Saz1, and Baquero F1. Departments
of Microbiology1 and Paediatrics2. "Ramon y Cajal" Hospital.
Madrid. Spain.
H. influenzae is a less common pathogen than Pseudomonas aeruginosa in cystic fibrosis patients, but it could also be considered as a chronic coloniser of bronchial secretions. Sputum and bronchial secretion specimens from 67 cystic fibrosis patients obtained in different periods during 1994 were microbiologically studied by a quantitative technique which included chocolate agar or chocolate agar plates supplemented with bacitracin for H. influenzae isolation. Susceptibility testing was performed by using both the standard agar-dilution and the agar disk-diffusion methods in Mueller-Hinton agar plates supplemented with sheep chocolate blood (5q6) and 2% IsoVitalex. H. influenzae was recovered from 12 patients (17.9%). In 10 patients, H. influenzae isolates were susceptible to nalidixic acid and fluorquinolones. Resistant or less susceptible isolates were recovered from the 2 remaining patients (A and B), one of them (patient A) chronic colonized by this organism. Susceptibility patterns (MIC range, Fg/ml) to quinolones were as follows:
Antibiotic susceptible isolates resistant isolates
(n=12) PatientA (n=7) Patient B (n=1)
Nalidixic ac 0.2 - 1 64 - >64 >64
Norfloxacin 0.06 - 0.2 8 - 32 32
Pefloxacin 0.03 - 0.2 4 - 16 64
Ofloxacin 0.03 - 0.06 2 - 8 64
Ciprofloxacin <0.01 - 0.03 0.5 - 2 32
The retrospective analysis in patient A and B revealed the presence of H. influenzae isolates with similar quinolone resistance phenotype preceded by quinolone susceptible isolates. Both patients had received fluoro-quinolone agents prior to the recovery of quinolone resistant H. influenzae isolate. The use of fluorquinolone agents in cystic fibrosis patients might be associated with the emergence of quinolone resistance in H. influenzae isolates.