A Study On The Relationship Between Active Efflux Pump MexAB-OprM Of Pseudomonas Aeruginosa And Carbopenem Resistant Mechanizam

ObjectiveTo probe the relation between active efflux pump MexAB-OprM in clinical isolated Pseudomonas aeruginosa strains from our hospital and the carbopenem resistance,and study its molecular mechanism of drug resistant.MethodPseudomonas aeruginosa clinical isolates were collected in the laboratory department of the first hospital affiliated to Shan Xi medical university.We selected 20 stains which were resistant to imipenem and/or meropenem,and selected 20 strains which were sensitive to imipenem and meropenem.A standard quality control strain of PA ATCC27853 was also studied.Antimicrobial susceptibility of the 41 isolates were test by Kirby-Bauer method against inipenem and meropenem. The strains are divided into Carbapenems-resistant group and Carbapenems- sensitive group according to carbopenems sensitivity;RT-PCR method was used to study the level of mRNA expression of oprM which is the structural gene in active efflux pump MexAB-OprM; PCR method was used to amplify the mexR gene of these two group strains, and analyze the PCR products with DNA sequencing.Result1.Antimicrobial susceptibility of the 41 isolates were consistent with the result of the laboratory department of the hospital. 20 stains which were resistant to imipenem and/or meropenem were enrolled into Carbapenems-resistant group. 20 strains which were sensitive to imipenem and meropenem were enrolled into Carbapenems-sensitive group.2.The expression level of mRNA of oprM in the strains of the Carbapenems-resistant group was higher significantly than those in Carbapenems-sensitive group(p<0.05).3.One risitant strains had the amino acid substitution in MexR protein, Val(GTG)→Glu(GAG),at the position of amino acid 126.Two strains had the amino acid substitutionin of Arg(CGG)→Gln(CAG),at the position of amino acid 70. No amino acid was found in the rest of Carbapenems-resistant isolates and Carbapenems-sensitive isolates.Conclusion1.In The First of Affiliated Hospital of Shan Xi Medical University, high expression active efflux pumps in clinical isolated Pseudomonas aeruginosa mediate the resistant to carbopenem;2.High level expression of MexAB-OprM was relative to mexR gene mutation and other mutant type.