[Epidemiology of Haemophilus influenzae strains collected in 2004 in France and in vitro assessment of their susceptibility to antibiotics].

Objectives: The aim of this study was to describe the epidemiology of H. influenzae strains collected in 2004 at the National Reference Center and to evaluate their susceptibility to various antibiotics.

Methods: Demographic and clinical characteristics, capsular serotyping by slide agglutination with specific antisera, beta-lactamase by a chromogenic cephalosporin test (Nitrocefin) and MICs of amoxicillin, co-amoxiclav, cefpodoxime, cefaclor, cefuroxime, cefotaxime, erythromycin, pristinamycin and telithromycin by agar dilution method on Haemophilus Test Medium were determined for each strain.

Results: 807 strains of H. influenzae were identified: 41.8% from bronchial secretions (BS), 16.2% from conjunctivitis, 6.6% from otitis media (OM), 4.2% from CSF and 8.6% from blood cultures. 95.6% of strains was not capsulated and 4.4% was of serotype b, e, or f. 26.3% of strains was beta-lactamase producing (TEM type). 185 isolates (22.8% of total strains) had reduced susceptibility to beta-lactams due to modification of the target associated or not with beta-lactamase production. When beta-lactamase was produced, the MICs of amoxicillin increased, but the activity of the other antibiotics was unchanged. Low BLNAR strains showed an increase in the MICs of all beta-lactams. This increase was weak and variable according to beta-lactams. Pristinamycin and telithromycin activities were unchanged against these strains. Two strains were resistant to erythromycin.

Conclusions: Theses results show that both beta-lactamase and modifications of the target are widespread among H. influenzae strains isolated in France. Cefpodoxime remains the most active compounds against H. influenzae, whatever the resistance mechanisms, followed by pristinamycin, telithromycin, and co-amoxiclav.