Role of efflux pump MexAB-OprM in multi-drug resistant Pseudomonas aeruginosa

Objective:To study the effect of efflux pump inhibitors(CCCP) on several antibiotic in multidrug resistant Pseudomonas aeruginosa(P.aeruginosa) clinical isolates and investigate the association between the resistance to antibiotic or mechanism and expression levels of efflux pump of P.aeruginosa.Methods:MexB gene of 30 strains were detected by PCR;The mRNA expression levels of efflux pump gene(MexB) were quantified by real time fluorescent quantitative PCR;MICs of antibiotic combined with efflux pump inhibitors(CCCP) against multiple resistant strains were determined by agar dilution method,and changes of MICs were observed.Results:Combined with efflux pump inhibitors(CCCP),the MICs of gentamicin(GEN)and ciprofloxacin(CIP) was downregulated for 2-fold in most isolates,even significantly for 4-fold or more in four isolates.But the resistant rate didn′t prove any significant difference(P0.05).Overexpression of efflux pump(MexAB-OprM) gene were present in all of the 30 isolates,and the group of Multidrug Resistance isolates were about 36.5 times more than the group of the sensitive isolates.When the concentration of CCCP were 7.5 μg/ml,with regard to Gentamicin(GEN),ciprofloxacin(CIP),tetracycline(TET),there is significant differences between the MICs of strains of the same or increased(≥1MIC group) and the MICs of strains decreased(≤1/2MIC group) on the relative expression of efflux pump(P0.05).However,in regard to cefotaxime(CTX),there is no significant differences between the MICs of strains of the same or increased(≥1MIC group) and the MICs of strain decreases(≤1/2MIC group) on the relative expression of efflux pump(P0.05).Conclusion:Efflux pump MexAB-OprM plays an important role in the clinical isolates of multi-drug resistant Pseudomonas aeruginosa.There was a strong relationship between overexpression of efflux pump(MexAB-OprM) gene and the resistance of Mpa to Gentamicin and ciprofloxacin,maybe a basic or intrinsic mechanism.But a little influence to cefotaxime.And there is also a direct amount relationship between the relative expression of efflux pump of MexAB-OprM and the resistant to Gentamicin.ciprofloxacin and tetracycline,Details need to be explored in the future.