Study of active efflux in ciprofloxacin-resistant Enterobater cloacae isolates

Objective:To detect whether active efflux system is present in ciprofloxacin-resistant Enterobater cloacae (E.cloacae) isolated from clinic. Methods:The accumulations of ciprofloxacin in E. cloacae isolates were measured by a fluorescence method and the effects of carbonyl cyanidem-chlorophenylhydrazone (CCCP)in the uptake of ciprofloxacin in E.cloacae isolates were evaluated by comparing intracellular stable concentrations of ciprofloxacin with CCCP and without CCCP. Results:The accumulations of ciprofloxacin detected in E.cloacae isolates reached to stable concentrations within the first 5 min, while the intracellular stable concentrations of ciprofloxacin showed lower in ciprofloxacin-resistant isolates than in ciprofloxacin-sensitive isolates, the accumulations of ciprofloxacin in resistant isolates increased after incubated with CCCP. Conclusion:It maybe exist an energy-dependent active efflux system targeting ciprofloxacin in ciprofloxacin-resistant E.cloacae isolates and the active efflux system may play a role in resistance to ciprofloxacin of E.cloacae isolates.