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 Haem ophilus influenzae (n = 1352) and Moraxella catarrhalis (n = 428) were coll ected by 18 Canadian medical centres. beta-Lactamase was produced by 24.0 a nd 94.2% of H. influenzae and M. catarrhalis isolates, respectively. Resist ance rates for H. influenzae were highest for ampicillin (24.0%), trimethop rim/sulphamethoxazole (13.7%), loracarbef (6.1%) and cefaclor (4.2%), and l ess than or equal to 1% for amoxycillin/clavulanate, cefotaxime, cefprozil, cefixime, imipenem, ciprofloxacin, levofloxacin, grepafloxacin, trovafloxa cin and chloramphenicol. M. catarrhalis resistance rates, derived using NCC LS breakpoint criteria for Haemophilus spp., were less than or equal to 1% for all antibiotics tested except ampicillin (49.5%) and trimethoprim/sulph amethoxazole (1.6%).