Natural Inhibitors of Salmonella MDR Efflux Pumps AcrAB and AcrD: An Integrated In Silico, Molecular, and In Vitro Investigation

Abstract

Multidrug-resistant (MDR) <i>Salmonella</i> remains a significant global health threat. This study aimed to explore the potential of essential oil components as novel inhibitors of the <i>Salmonella</i> MDR efflux pumps AcrAB and AcrD. <i>Salmonella</i> isolates were characterized for serotype, antibiotic resistance, and efflux pump activity. Essential oil components were screened for inhibitory effects using phenotypic and genotypic methods. In silico docking and molecular dynamics simulations were conducted to investigate binding interactions and stability. <i>Salmonella Typhimurium</i> was the predominant serotype with high MDR rates. Efflux pump activity was prevalent. Cumin and cinnamon oils demonstrated promising inhibitory effects on these pumps. Molecular docking simulations revealed strong binding affinities of analyzed compounds to the AcrAB and AcrD binding pocket. The 2-methyl-1-(p-tolyl)propan-2-ol exhibited higher stability within the AcrAB binding pocket compared to (1S,3R,5R)-1-isopropyl-4-methylenebicyclo[3.1.0]hexan-3-ol within the AcrD binding pocket. Treatment with these oils significantly downregulated efflux pump genes (<i>robA</i>, <i>acrB</i>, <i>mdtB</i>, <i>acrF</i>, <i>acrD</i>, <i>soxS</i>, <i>mdsB</i>, <i>marA</i>). The novel approach of combining in silico and molecular dynamics simulations with precise gene expression analysis provides a valuable framework for future studies aimed at combating MDR <i>Salmonella</i> efflux pumps.