In vitro susceptibility of some antimicrobials against bacteria enteropathogens

To investigate the current resistant levels of enteric bacteria in southwestern China, broth dilution method was used to detect in vitro susceptibility of rifaximin, ciprofloxacin, gatifloxacin, azithromycin and trimethoprim/sulfamethoxazole (SMZ/TMP) against 101 enteropathogens isolated from cases of bacterial diarrhea of four teaching hospitals. For all the isolates, ciprofloxacin, gatifloxacin and SMZ/TMP had MIC(90)s of 64, 32 and >128 mg/L, respectively, much higher than CLSI resistance cutoffs. Azithromycin also had very high MIC(90) value of >128 mg/L. The MIC(90) of rifaximin was 64 mg/L, much lower than the intestinal lumen concentration measured after administration of this agent. Diarrheagenic Escherichia coli were highly resistant to fluoroquinolones with resistant frequency of >40%. The in vitro activity of ciprofloxacin, gatifloxacin and azithromycin on Shigella spp was of concern with the MIC(90)s of 64, 16 and 64 mg/L, respectively. The majority of Salmonella spp isolated retained susceptibility to the antimicrobials tested. Comparing with other regions or countries, resistance rates of enteropathogens were much higher in this area of China. Rifaximin is a promising treatment and chemophylaxis for nonsystemic bacteria diarrhea.