TABLE 2.

Measurements of L. monocytogenes phagosomal escape and cell-to-cell spread

Strain	% Phagosomal escapea ± SD	Plaque sizeb (%) ± SD
Lmdd	65 ± 9	100
HG-L2001	47 ± 9*	91 ± 3.4†
HG-L2002	37 ± 10†‡	61 ± 4.6†
HG-L2003	39 ± 9†	0
HG-L2004	28 ± 10†	0
HG-L2005	36 ± 13†	0

^aThat is, the percentage of total intracellular bacteria staining with Alexa Fluor 568 phalloidin at 90 min after infection of J774 cells. Two-tailed P values of unpaired t tests are indicated as follows: *, P < 0.05; †, P < 0.001 compared to values obtained with the Lmdd strain; ‡, P < 0.05 compared to values obtained with-HG-L2001. At least 200 bacterium-associated macrophages were counted for each of three experiments.

^bThat is, the plaque size relative to that of strain Lmdd. A minimum of 10 plaques per strain per experiment were measured. Values are means of three independent experiments. Two-tailed P values of unpaired t tests are classified as follows: †, P < 0.001 compared to values obtained with the Lmdd strain.