Role of Efflux System on Multi-resistance of Pseudomonas aeruginosa

OBJECTIVE To investigate the effect of efflux inhibitor carbonyl cyanide m-chlorophenylhydrazone(CCCP) on the resistance of Pseudomonas aeruginosa,the encoding gene for efflux pump and the relationship between efflux pumps and resistance of P.aeruginosa.METHODS Two-fold agar dilution was used to determine the minimum inhibitory concentrations(MIC) of tetracycline,chloramphenicol,ciprofloxacin,gentamicin,cefotaxime,imipenem and meropenem of 150 P.aeruginosa strains,and observe the variation of MIC with 5mg/L CCCP.PCR was used to detect the oprM,mexB and mexR genes.RESULTS Of 150 isolates,84(56.0%) strains were positive in phenotype tests of efflux pump.At least four fold decrease in MIC was observed in 17,6,12,29,35,18 and 31 isolates for tetracycline,chloramphenicol,ciprofloxacin,gentamicin,cefotaxime,imipenem and meropenem with 5mg/L CCCP.56.0%(47/84) Strains were found to have an evident exfflux effect against more than two antibiotics.efflux mechanism existed not only in resistant strains,but also in sensitive ones.But the effect of CCCP on resistant strains was much stronger than that on susceptible strains.oprM,mexB And mexR genes could befound in P.aeruginosa universally.CONCLUSIONS The resistance of P.aeruginosa is related to the effect of the efflux system.Efflux pump inhibitors may reduce the MIC of antibacterials in vitro.In certain cases,the efflux inhibitor could be used to overcome the bacterial resistances in clinic.