Beyond antimicrobial resistance: MATE-type efflux pump FepA contributes to flagellum formation and virulence in Listeria monocytogenes.

Listeria monocytogenes is commonly found in nature and can readily contaminate various food products. Efflux pump proteins represent an essential group of proteins in bacteria, playing key roles in numerous biological processes. This study investigates the contribution of FepA to motility and virulence apart from antimicrobial resistance in L. monocytogenes. The minimum inhibitory concentrations of various antimicrobials and the survival of L. monocytogenes in medium containing these agents were assessed. Loss of FepA increased sensitivity to a range of antimicrobial agents and significantly impaired growth under antimicrobial pressure. We examined bacterial flagellum formation, flagellar gene transcription, and protein expression. Results indicated a marked decrease in flagellum formation in ΔfepA mutants, owing to reduced expression of key flagellar proteins such as FlhF and FlgG. In addition, results from cell infection, virulence genes transcription, and protein expression experiments revealed that FepA deletion diminished bacterial invasiveness and intracellular proliferation, correlating with decreased secretion of virulence proteins, including InlB, InlC, Mpl, PlcA, and LLO. These findings indicate that FepA is integral not only to antimicrobial resistance and in vitro adaptability but also to flagellar formation and virulence. This research helps deepen the understanding of mechanisms underlying drug resistance and pathogenicity in the significant foodborne pathogen L. monocytogenes.

Importance: Listeria monocytogenes is a significant zoonotic foodborne intracellular pathogen with a mortality rate of up to 20%-30%. This bacterium employs various mechanisms, including efflux pumps, to enhance its environmental adaptability and maintain infectivity. In this study, we discovered that the MATE-type multidrug efflux pump protein FepA is not only associated with bacterial resistance to multiple antimicrobials but also plays a crucial role in promoting flagellum formation, which is essential for motility and resistance to adverse environmental conditions. Additionally, FepA is involved in the secretion of virulence proteins, facilitating bacterial invasion and proliferation within the host. Our findings reveal, for the first time, that the multidrug efflux pump FepA contributes to flagellar formation and virulence, providing new insights into the mechanisms of environmental adaptation and virulence expression in L. monocytogenes and aiding in the discovery of potential therapeutic targets.