Antimicrobial Resistance among Salmonella and Shigella Isolates in Five Canadian Provinces (1997 to 2000)

OBJECTIVE: To describe rates of antimicrobial resistance (AMR) among Salmonella and Shigella isolates reported in five Canadian provinces, focusing on clinically important antimicrobials. METHODS: The authors retrospectively investigated AMR rates among 6219 Salmonella and 1673 Shigella isolates submitted to provincial public health laboratories in Alberta, Newfoundland and Labrador, Ontario, Prince Edward Island and Saskatchewan from 1997 to 2000; these isolates were estimated to represent 41% of Salmonella cases and 72% of Shigella cases reported by the study provinces. RESULTS: Among Salmonella isolates, 27% (1704 of 6215) were resistant to ampicillin, 2.2% (135 of 6122) to trimethoprim/ sulfamethoxazole, 1.5% (14 of 938) to nalidixic acid, 1.2% (one of 84) to lomafloxacin and 0.08% (five of 6163) to ciprofloxacin. Among Shigella isolates, 70% (1144 of 1643) were resistant to trimethoprim/sulfamethoxazole, 65% (1079 of 1672) to ampicillin, 3.1% (eight of 262) to nalidixic acid, 0.49% (eight of 1636) to ciprofloxacin, 0.14% (one of 700) to ceftriaxone and 0.08% (one of 1292) to ceftazidime. CONCLUSIONS: Higher rates of resistance to clinically important antimicrobials (including ciprofloxacin) were observed among both Salmonella and Shigella isolates than has previously been reported. Current Canadian data on rates of AMR for these pathogens are required.