The mechanism of efflux pumps in clinical isolated multidrug-resistant Pseudomonas aeruginosa strains

Objective To explore the expression of outer membrane protein OprM of MexA-MexB-OprM efflux pump and the mutation of regulation gene mexR of MexA-MexB-OprM in multidrug-resistant Pseudomonas aeruginosa isolated from clinic.Methods Thirteen multidrug-resistant and 5 antimicrobial susceptible Pseudomonas aeruginosa isolates from clinical specimens were screened.Outer membrane proteins were analysed with SDS-PAGE.MexR was amplified with PCR and PCR products were analyzed with DNA sequencing.Results The grey density of multidrug-resistant bacterial OprM bands near 49 kD increased obviously compared with that of susceptibile and control strain ATCC 27853,the optical density of multidrug-resistant strains and susceptible strains was 157.79 and 132.03 respectively,there was significant difference between two groups(t=(19.345),P(0.01));The main sites of point mutation were A-96→G,G-411→A,C-308→G,T-377→A,the latter two mutations resulted in the change of amino acid sequence,which was Ala-103→Gly,Val-126→Glu respectively.Conclusion The increased expression of OprM suggests that MexA-MexB-OprM efflux pump involves in multidrug resistance. The mexR genes of multidrug-resistant bacterial strains have point mutation,which sugget that mexR gene mutation can result in high level expression of MexA-MexB-OprM.