Antibiotic resistance in respiratory tract isolates of Haemophilus influenzae and Moraxella catarrhalis collected from across Canada in 1997-1998

Between September 1997 and November 1998 respiratory tract isolates of Haemophilus influenzae (n = 1352) and Moraxella catarrhalis (n = 428) were collected by 18 Canadian medical centres. beta-Lactamase was produced by 24.0 and 94.2% of H. influenzae and M. catarrhalis isolates, respectively. Resistance rates for H. influenzae were highest for ampicillin (24.0%), trimethoprim/sulphamethoxazole (13.7%), loracarbef (6.1%) and cefaclor (4.2%), and less than or equal to 1% for amoxycillin/clavulanate, cefotaxime, cefprozil, cefixime, imipenem, ciprofloxacin, levofloxacin, grepafloxacin, trovafloxacin and chloramphenicol. M. catarrhalis resistance rates, derived using NCCLS breakpoint criteria for Haemophilus spp., were less than or equal to 1% for all antibiotics tested except ampicillin (49.5%) and trimethoprim/sulphamethoxazole (1.6%).