Expression of MexAB-OprM efflux pump and OprD porin in carbapenemase producing Pseudomonas aeruginosa clinical isolates

In recent years, the prevalence of carbapenem resistant of Pseudomonas aeruginosa isolates has become a global concern. The aim of this study was to examine the relationship between the expression of efflux pump and OprD genes in Metallo-beta-lactamase (MBL) and Klebsiella pneumoniae carbapenemase (KPC) producing P. aeruginosa isolates.The study was performed on the 97 P. aeruginosa strains that were isolated from clinical samples in Hamadan hospitals, western Iran in 2017–2018. Antibiotic susceptibility testing was performed using disk diffusion and Minimal Inhibitory Concentration (MIC) methods. Carbapenemase production enzymes was identified by Imipenem-EDTA combined disc (ECD) and Modified Hodge Test (MHT) and Polymerase chain reaction (PCR). Expression levels of efflux pump and OprD genes were mesured by Real-Time PCR (RT-PCR). Finally, the relationship between the presence of carbapenemase enzymes with expression levels of efflux pump and OprD genes was analyzed with chi-square test. The results, showed that the highest resistance was to cefoxitin 92 (94.8%) and the lowest resistance was to piperacillin-tazobactam 38 (39.2%). Also, among of the carbapenem antibiotics, the highest resistant was to imipenem 48 (49.4%) and the lowest resistant was to meropenem 40 (41.2%). Out of 49 (51.51%) Carbapenem resistant isolates, 42 (85.7%), 25 (51.02%) and 26 (53.06%) isolates had positive results for MIC, MHT, and ECD tests, respectively. The highest and lowest presence of the carbapenemase genes in P.aeruginosa isolates was related to the IMP 20 (40/80%) and AmpC 12 (24.4%) genes, respectively. Out of 20 selected isolates, decreased and increased expression level of the OprD, MexA, MexB and OprM genes were observed in 60% (12/20), 55% (11/20), 60% (12/20) and 55% (11/20), of isolates, respectively. This study demonstrated that there was a significant relationship between the presence of carbapenemase enzymes (MBL and KPC) and expression level of efflux pump and OprD genes (P-value <.05).