A Comprehensive Review of the Multitarget Effects of Subinhibitory Concentrations of Essential Oils Against Salmonella

Essential oils (EOs) exhibit antimicrobial activity against foodborne pathogens due to their chemical composition. This review investigates the mechanisms of action of EOs at subinhibitory concentrations against Salmonella strains. Even at subinhibitory concentrations, EOs induce cellular stress and modulate bacterial metabolism. EOs interfere with quorum sensing (QS) by downregulating genes (luxS, pdfs, sdiA, and qseB), which are essential for the system's function, affecting biofilm formation and virulence expression. Additionally, EOs act as antibiofilm agents, reducing cell adhesion and biomass of mature biofilms. At the molecular level, they regulate genes associated with biofilm formation (csgA, csgB, and csgD) and bacterial motility (motB, flhD, and fliZ). The combination of EOs with conventional antibiotics has shown synergistic effects. A proposed mechanism for this action is the inhibition of efflux pumps, which favors the retention of antimicrobial agents inside the cell. Despite promising results, challenges such as the sensory impact of high EOs concentrations and the need for further standardization in their application remain. Future research should focus on the long-term effects of subinhibitory concentrations of EOs, bacterial molecular response mechanisms, and the development of new delivery systems to optimize the efficacy of EOs.