Fig 6.

Invasion and intracellular growth of S. Enteritidis strain E40 control cells and filaments in Caco-2 cells. (Top) Differentiated Caco-2 cells were incubated with E40 control cells (7.49 log₁₀ CFU) or filaments (7.43 log₁₀ CFU for filaments and 6.55 log₁₀ for filaments at 1:10) at 37°C for 1.5 h to allow invasion, followed by incubation with gentamicin (50 μg/ml) for 2.5 h to kill any extracellular Salmonella. Some of the wells were assayed for Caco-2 cell invasion; the others were incubated for 12 h in fresh tissue culture medium with gentamicin (5 μg/ml) and assayed for intracellular growth. Letter above right-most bar: a, intracellular growth was significantly different from control and filaments (P < 0.05). (Bottom) Differentiated Caco-2 cells were incubated with E40 control cells (42 μg [wet weight]) or filaments (42 μg or 420/840 μg [wet weight]) and assayed for invasion and intracellular growth as described above. For the greater mass of filaments, data were averaged from two separate trials in which 420 μg of E40 was used in one trial and 840 μg in the second. Letter above middle bar: a, invasion and intracellular growth was significantly different from control and filaments (420/840 μg [wet weight]) (P < 0.05).