The association between resistance phenotypes and expression levels of efflux pump—MexAB-OprM of multidrug resistance Pseudomonas aeruginosa

Objective To study the effect of efflux pump inhibitors(CCCP) on several antibiotic in multidrug resistance 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 and ciprofloxacin 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 60 times more than the group of the sensitive isolates.Conclusion Efflux pump MexAB-OprM plays an important role in the clinical isolates of multi-drug resistant Pseudomonas aeruginosa. When the concentration of CCCP were 7.5 μg/ml,the effort on antibacterial activity of cefotaxime were small,while the efforts on gentamicin and ciprofloxacin were relatively more.As a result,there was a strong relationship between overexpression of efflux pump(MexAB-OprM) gene and multidrug resistance Pseudomonas aeruginosa,maybe a basic or intrinsic mechanism. Details need to be explored in the future.