Investigation of MexAB-OprM efflux pump gene expression in clinical isolates of pseudomonas aeruginosa isolated from Intensive Care Unit

Pseudomonas aeruginosa is one of the most important pathogens of nosocomial infections, especially in the ICU (Intensive Care Unit), which has resistance to a wide range of antibiotics, especially Carbapenems. Among the most important resistance mechanisms of this bacteria against carbapenems are MexAB-OprM efflux pump. Therefore, the aim of this study was to evaluate the gene expression of MexAB-OprM efflux pump in clinical isolates of P. aeruginosa that isolated from ICU.

 A total of 33 sampales were isolated from patient in ICU units from different Hamadan hospitals, since november 2018 to May 2019. Antibiotic susceptibility testing was performed using disk diffusion and Minimal Inhibitory Concentration (MIC) methods by Etest for imipenem. Expression levels of MexAB-OprM efflux pump genes were measured by Real-Time PCR.

The results of statistical analysis showed that the highest resistance was to Ceftriaxone 21 (63.63%) and the lowest resistance was to piperacillin, 11 (33.33%). The results of the MIC of imipenem showed that among off 33 samples isolated from the ICU, 14 (42.42%) and 19 (57.57%) isolates were resistant and susceptible, respectively. Increased expression of of MexA, MexB and OprM genes compared with control strain were observed in 20% (4/20), 25% (5/20) and 20% (4/20) of isolates, respectively.

Increased expression of MexAB-OprM efflux pump is one of the most common mechanisms in the resistance of P. aeruginosa isolates against Carbapenem antibiotics in different units of hospitals especially intensive care unit. So identification of resistance mechanisms to Carbapenem antibiotics can be useful in controlling and treating such resistant isolates.