Antimicrobial susceptibilities of clinical isolates of Haemophilus influenzae and Moraxella catarrhalis collected during 1999-2000 from 13 countries.

To determine antimicrobial activity against Haemophilus influenzae and Moraxella catarrhalis.A central laboratory performed NCCLS susceptibility testing for all isolates and beta-lactamase and capsular serotype determinations for H. influenzae.A total of 2712 H. influenzae and 1079 M. catarrhalis were collected. H. influenzae susceptibilities were >90% for amoxicillin/clavulanate, cefaclor, loracarbef, cefprozil, cefuroxime, ciprofloxacin, azithromycin and clarithromycin and were <80% for trimethoprim/sulfamethoxazole and ampicillin. 19.3% were beta-lactamase positive. The most common serotype was type-b (5.6%); 86.1% were nontypeable. M. catarrhalis had MIC90 within therapeutic range for all antimicrobials except ampicillin.The conclusion of the study is that antimicrobials, except ampicillin and trimethoprim/sulfamethoxazole, remain good empiric choices against H. influenzae and M. catarrhalis.