In vitro activity of norfloxacin and other antibacterial agents against gastro‐intestinal pathogens isolated in Sweden

The in vitro activity of norfloxacin was compared to that of ampicillin, doxycycline, chloramphenicol, trimethoprim in combination with sulfamethoxazole (1/20), and erythromycin, against 272 clinical isolates of gastro-intestinal pathogens. Norfloxacin was the most active compound of those tested with MICs in the range 0.004-2 mg/l. Concentrations inhibiting 90% of the strains (MIC 90) were 0.008 mg/l for Vibrio cholerae, 0.016 mg/l for Aeromonas hydrophila, 0.032 mg/l for Vibrio cholerae non 01, 0.064 mg/l for Vibrio parahaemolyticus, Yersinia enterocolitica 03, enterotoxigenic (ETEC) and enteropathogenic (EPEC) Escherichia coli and Shigella species, 0.125 mg/l for Salmonella species, and 0.5 mg/l for Campylobacter species. Resistance to one or several of the other drugs was seen with higher or lower frequency in all the bacterial species tested. No cross-resistance between any of the other agents and norfloxacin was recorded.