Bacteriocinogenic Enterococcus faecium inhibits the virulence property of Listeria monocytogenes

This study investigated the effects of two meat-borne Enterococcus faecium strains, having different characteristics on virulence properties (the expression levels of six important virulence genes and the capacity to invade the Caco-2 cell) and on the survival of Listeria monocytogenes. The presence of real-time metabolic products of bacteriocinogenic E. faecium B1 played a key role in the lethal inhibition of L. monocytogenes. The expression of the six virulence genes (inlA, prfA, hlyA, bsh, actA, sigB genes) were already inhibited by E. faecium B1 to different extents at 0 h, and up-regulated between 0 h and 24 h. At 24 h, the expression of most virulence genes (except for sigB and hlyA genes) was decreased. Also, E. faecium B1 showed a stronger inhibition of the competitive adhesion of L. monocytogenes to Caco-2 cells. The direct contact between the cells was one of the key factors for inhibition of L. monocytogenes by non-bacteriocinogenic E. faecium B2, and its effect on the gene expressions of L. monocytogenes was lower than that of E. faecium B1. These results indicated that E. faecium B1 could potentially be used to reduce the virulence of this microorganism.