The process involved isolating E. faecium from the gut of honeybees, screening the bacterium for bacteriocin-like inhibitory substance (BLIS), evaluating its impact on the expression of the mexA gene in multidrug-resistant (MDR) P. aeruginosa, and determining the role of bacteriocin in treating infected wounds in mice through histopathological examination. After evaluating the best circumstances for producing BLIS, it was discovered that glucose was a superior carbon source and yeast extract was the best source of nitrogen. The pH was found to be 5, the ideal incubation time was 72 hours, and ammonium sulfate salt was used for partial purification at 80% saturation. The identification of MDR P. aeruginosa isolates from pus infections was a further focus of the study. The VITEK 2 system was used to perform the identification. The results of antibiotic susceptibility tests revealed that the greatest resistance rates were found against Meropenem (83.3%) and Gentamicin (73.3%), followed by beta-lactam antibiotics (Ticarcillin, Ticarcillin/Clavulanic Acid, Piperacillin, and Aztreonam), which showed resistance in about 66.6 and 36.6% of the study isolates, respectively. Followed by Imipenem (63.3%), Ceftazidime (36.6%), and Cefepime (36.6%). The mexA gene was detected in all nine strains. The study also investigated the impact of the bacteriocin of the chosen strain on the expression of the mexA gene. An in vivo study revealed that wound healing was enhanced by treating infected wounds with E. faecium bacteriocin. Conclusion: Down-regulation and up-regulation in the expression of the genes following exposure to Bacteriocin indicate the potential of E. faecium as an effective antimicrobial agent against MDR P. aeruginosa infections.
