Fig 2. In vitro virulence potential of L. monocytogenes strains.

(A)Invasion efficiency and (B) intracellular growth (IGC) of L. monocytogenes strains PL25-Rif^R, C5-Str^R, ScottA(Str^R/Rif^R) and 6179-Rif^R were determined using Caco2 cells. Bacteria were incubated for 1 day at 10°C in TSB-Y. Caco2 cells were infected for 1h with bacteria (multiplicity of infection of 25), incubated for 45 min (invasion) and 4h (intracellular growth) with gentamycin. IGC was calculated as the number of intracellular bacteria after 4h minus the number of bacteria after 45 min divided by the number of bacteria after 45min. Data, represented as % of invasion and IGC, are mean values ± standard deviation of three biological replicates performed in triplicate. Different letters indicate statistically significant differences between the strains (P<0.05). p-values are shown in S2 Table.