Infant-Type Bifidobacteria as Biocontrol Agents: Suppressing Listeria monocytogenes via Key Virulence Gene Alteration.

Infant-type bifidobacteria exhibit potential as targeted biocontrol agents against Listeria monocytogenes infections. However, the strain-specific antimicrobial efficacy and molecular mechanisms remain insufficiently characterized. In this study, the probiotic potential of five bifidobacteria strains was systematically evaluated through comprehensive in vitro antioxidant and antibacterial activities. Furthermore, RNA-seq analysis was employed to elucidate the global transcriptomic responses of L. monocytogenes during coculture with three selected bifidobacteria strains. The results revealed that the tested bifidobacteria strains possess significant in vitro antioxidant and antibacterial activities. Notably, three infant-type bifidobacteria strains exhibited particularly potent growth inhibition against L. monocytogenes. Co-incubation with these strains significantly reduced the survival of L. monocytogenes and modulated the expression of key genes. A substantial proportion of differentially expressed genes (DEGs) were enriched in pathways related to anion binding, ABC transporters, quorum sensing, peptidoglycan biosynthesis, and glutathione metabolism, suggesting common mechanisms underlying the inhibitory effects of infant-type bifidobacteria strains. Furthermore, several virulence-associated DEGs, including ahpC, clpC, clpX, recN, arlR, rpoD, tlyA, and hlyIII, were identified as shared antagonistic targets. Strain-specific DEGs, such as msrB, amiE, clpE, and clpL, were also identified, reflecting variations in virulence inhibition and stress-response mechanisms. These findings advance our understanding of probiotics-pathogen interactions and provide a foundation for developing targeted strategies to combat L. monocytogenes.