FIG. 4.

Early association with and invasion of HBMEC by L. monocytogenes EGD (WT), L. monocytogenes ΔinlB (ΔinlB), and L. innocua (L.i.). HBMEC were infected (multiplicity of infection = 20), and associated bacteria were counted at 35 min postinfection (left three bars). In parallel, the infected cells were washed and treated further with gentamicin for 1 h, the intracellular bacteria were enumerated (right three bars), and the number of recovered bacteria (as a percentage of the inoculum) is shown. The mean and standard deviations (error bars) of the results of one representative experiment are given. The differences in association with the HBMEC between the three strains are not significant (P > 0.05). The differences in invasion of HBMEC between L. monocytogenes and the two strains L. innocua and L. monocytogenes ΔinlB are highly significant (P < 0.001).