Subsequent to infection, approximately 10% of internalized bacteria are in the cytosol as early as 10 minutes post infection while approximately 80% of the bacteria are in the cytosol after 90 minutes [9] . Once in the cytosol, L. monocytogenes express the bacterial protein ActA to facilitate bacterial motility and ultimately cell-to-cell spread [10] [11] [12] . Intercellular spread begins between 3 and 5 hours post infection [13] [14] [15] . Following cell-to-cell spread, bacteria are contained within double-membrane vacuoles in a newly infected cell. The bacteria utilize two bacterial phospholipases (PI-PLC and PC-PLC) as well as LLO to escape from spreading vacuoles [1] .