Growth of Listeria monocytogenes on a RTE-meat matrix enhances cell invasiveness to mouse J774A.1 macrophages

It remains unclear whether the growth of Listeria monocytogenes on a ready-to-eat (RTE) meat matrix has an impact on the bacteriumʹs pathogenic abilities. In this study, we investigated the impact of environments on virulence by growing L. monocytogenes (F2365 strain) on brain heart infusion agar (BHI), tryptic soy agar (TSA), and RTE turkey meat matrices. Bacteria cultured from these media were harvested and used to infect mouse macrophage cell line J774A.1 with different MOIs to examine their invasion ability. At MOI = 10 and 50, the numbers of bacteria recovered from cells infected with turkey-meat-grown Listeria were significantly higher than those from the two nutrient-rich growth media. Additionally, MOI played a role in determining L. monocytogenes recovery rates, since significant differences were found amongst all three groups at low MOI, while no significant differences were found between BHI and TSA groups at high MOI. These results indicate that environmental changes affect the ability of L. monocytogenes to invade and survive intracellularly while grown on RTE-meat matrix.