Epidemiology of Haemophilus influenzae strains identified in 2001 in France, and assessment of their susceptibility to beta-lactams

The aim of this study was to describe the epidemiology of H. influenzae strains collected in 2001 at the National Reference Center and to evaluate their susceptibility to beta-lactams. Methods. - The demographic characteristics were recorded for each strain, then were determined their capsular serotyping (slide agglutination with specific antisera), as well as their B-lactamase production (chromogenic cephalosporin test, Nitrocefin), and their MICs (agar dilution method on Haemophilus Test Medium) for amoxicillin (AMX), co-amoxiclav (AMC), cefpodoxime (CPD), cefaclor (CEC), cefuroxime (CXM), and cefotaxime (CTX). Results. - 41.3% of the 752 strains were identified in bronchial secretions, 20.6% in conjunctivitis, 11.3% in otitis media, and 11% in blood cultures. 96.3% of the strains were not capsulated and 3.7% were of type b, d, e or f. 33.8% of the strains were B-lactamase producers (TEM type), 45.8% of these were identified in otitis pus and 27.7% in bronchial secretions. One hundred and forty-two strains (18.9%) presented reduced susceptibility to beta-lactams (modification of target) associated or not with bla+. MICs 50/90 against bla+ strains were: AMX 1/32, AMC 0.12/1, CTX 0.007/0.03, CPD 0.03/0.12, CEC 1/64, CXM 0.25/1. Against low BLNAR and bla+ strains, MICs 50/90 were: AMX 2/32, AMC 0.25/2, CTX 0.015/0.06, CPD 0.06/0.25, CEC 4/64, CXM 0.25/4. And against low BLNAR strains MICs 50/90 were: AMX 0.25/8, AMC 0.25/8, CTX 0.015/0.12, CPD 0.06/0.50, CEC 4/32, CXM 0.25/4. Conclusions. - Both bla+ and modifications of PBP are widespread among strains isolated in France. CTX, and CPD remain the most active compounds whatever the resistance mechanisms. (C) 2003 Elsevier SAS. Tous droits reserves.