TABLE 2.

Entry of IH11128 bacteria into Caco-2/TC7 cells as a function of the day in culture^a

Day in culture	Levels of bacteria in CFU/ml ± SEM		Expression ofb:		Cell developmentc
	Cell associated	Intracellular	SI	CD55
2	1.20 × 102 ± 0.26 × 102	7.64 × 102 ± 2.89 × 102 (0.64)	0	1.05	Isolated cells
4	4.25 × 106 ± 0.43 × 106	1.02 × 104 ± 0.46 × 104 (0.24)	0	1.18	Clusters of cells
6	2.10 × 107 ± 0.34 × 107	3.23 × 104 ± 0.55 × 104 (0.15)	0.80	1.15	Confluency
15	2.55 × 107 ± 0.66 × 107	9.45 × 102 ± 0.67 × 102 (0.0037)*	2.65	1.41	Postconfluency

^aAt each day in culture, cells were infected with IH11128 bacteria for 3 h at a multiplicity of infection of 100, and the level of cell-associated bacteria was determined. The level of intracellular bacteria was determined by gentamicin assay. The values in parentheses are the percentages of cell-associated bacteria that were also intracellular. An asterisk represents a P value of <0.01 compared with intracellular bacteria at days 4 and 6 in culture, respectively (Student's t test). 

^bThe relative immunofluorescence intensities (arbitrary units) of the differentiation marker SI and the GPI-anchored protein CD55 were measured by conventional epifluorescence microscopy coupled with an image analyzer. 

^cThe cells were examined by light microscopy to determine the evolution of the cells in culture from cells organized in clusters to cells in monolayer. Days 2 and 4, cells proliferate; day 6, cell differentiation commences; day 15, cell differentiation is achieved and the cells are fully differentiated.