FIG. 4.

Growth of L. monocytogenes in BeWo cells and J774 murine macrophages. BeWo cells (3 × 10⁴) and J774 cells (6 × 10⁴) were plated on glass coverslips and grown overnight, leading to formation of monolayers. The difference in the number of plated BeWo and J774 cells reflects the difference in size between these two cell types. Cells were infected with a 1:20,000 dilution of an overnight culture of wild-type L. monocytogenes, resulting in MOIs of 1:8 for BeWo cells and 1:15 for J774 cells. At the specified times after infection, cells were lysed, and the number of bacteria per coverslip was determined in triplicate. In each case, gentamicin (50 μg/ml) was added 1 h after infection. Each growth curve represents the means and standard deviations from three separate experiments.