Role of MexAB-OprM and MexXY-OprM efflux pumps in carbapenem-resistant Pseudomonas aeruginosa from burn wounds.

Authors

Shahin Khalilipanah, Hadi Sedigh Ebrahim-Saraie, Iraj Nikokar, Hamed Naziri, Meysam Hasannejad-Bibalan

Published in

Molecular biology reports. Volume 53. Issue 1. Jul 10, 2026. Epub Jul 10, 2026.

Abstract

Pseudomonas aeruginosa remains a major cause of burn wound infections and exhibits a remarkable ability to develop resistance to carbapenems, primarily through multidrug efflux systems belonging to the Resistance-Nodulation-Division (RND) family. This study investigated the contribution of the MexAB-OprM and MexXY-OprM efflux pumps to carbapenem resistance in P. aeruginosa isolates from burn wounds and evaluated the effect of an efflux pump inhibitor on antibiotic susceptibility.
A total of 100 P. aeruginosa isolates were collected from burn patients. Antimicrobial susceptibility to imipenem and meropenem was determined by minimum inhibitory concentration (MIC) assays according to CLSI guidelines. The presence of mexAB-oprM and mexXY-oprM genes was confirmed via PCR. The functional role of efflux activity was assessed using carbonyl cyanide 3-chlorophenylhydrazone (CCCP), a proton-motive force inhibitor, and MIC reductions ≥ 4-fold were interpreted as efflux-mediated resistance.
Resistance to imipenem and meropenem was observed in 44% and 27% of isolates, respectively. Among imipenem-resistant isolates, mexXY-oprM was detected in 50% and mexAB-oprM in 18%, while 23% co-presented both systems. In contrast, mexAB-oprM predominated in meropenem-resistant strains (48%), followed by mexXY-oprM (22%). Upon CCCP addition, MICs decreased by ≥ 4-fold in 84% of imipenem-resistant and 52% of meropenem-resistant isolates, suggesting the involvement of efflux pumps (P < 0.05).
A high prevalence of carbapenem resistance and efflux pump-associated genes was observed among P. aeruginosa isolates from burn wound infections. Significant reductions in carbapenem MICs following CCCP exposure suggest that efflux-mediated mechanisms may contribute to the resistance phenotype in a substantial proportion of isolates. These findings indicate a potential role for efflux activity in carbapenem resistance and warrant further investigation of its clinical and mechanistic significance.

PMID:
42429867
Bibliographic data and abstract were imported from PubMed on 10 Jul 2026.

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