Mutant Prevention Concentration (MPC) of Fluoroquinolones to Streptococcus Enterobacter Cloacae

Objective To determine the mutant prevention concentration(MPC) in vitro of quinolones fagainetor the clinical Enterobacter cloacae,and guide the clinical rationable use of the agents.Methods The minimal inhibitory concentrations(MIC) of gatifloxacin,ciprofloxacin and ofloxacin Enterobacter cloacae were determined by agar twofold dilution method,and calculat the MIC50 and MIC90.MPC were determined by agar twofold dilution with bacterial population inocubated 1.2×1010 CFU,and were defined as the lowest drug concentrations that prevented recovery of colonies after 48 hours.Calculated the MPC50,MPC90 and compared the result of MPC with MIC.Results The MPC50 and MPC90 of gatifloxacin,ciprofloxacin and ofloxacin were 6,4,24 μg/ml and 8,10.5,6.Conclusion Three agents were all between MIC and MPC,which suggested the agents could not restrict the selective enrichment of resistant mutants while being used alone.Due to the tendency of resistant mutants selection,gatifloxacin,ciprofloxacin and ofloxacin should be administered in combination with other agents.