Interaction of <i>S</i>. Typhimurium ST19 and ST313 with macrophage cell lines.

<p><b>(A)</b> J774 murine macrophages were infected with four strains of <i>S</i>. Typhimurium ST19 (I77, I41, S52 and I89), five strains of ST313 (D65, Q55, S11, S12 and A13), <i>S</i>. Typhimurium SL1344 (ST19), <i>S</i>. Typhi Ty2 and <i>S</i>. Paratyphi A ATCC9150. The ability of these strains to be phagocytosed by J774 macrophage cells was determined 30 min p.i. <b>(B)</b> U937 human macrophages were infected with four strains of <i>S</i>. Typhimurium ST19 (I77, I41, S52 and I89), five strains of ST313 (D65, Q55, S11, S12 and A13), <i>S</i>. Typhimurium SL1344 (ST19), <i>S</i>. Typhi Ty2 and <i>S</i>. Paratyphi A ATCC9150 in a gentamicin protection assay. Percent survival was expressed as the number of intracellular bacteria at 24 h p.i. divided by the number of intracellular bacteria at 0 h p.i. times 100. <b>(C)</b><i>S</i>. Typhimurium I77 (ST19) and D65 (ST313) were used to infect human THP-1 cells. <i>S</i>. Typhimurium SL1344 (ST19) and <i>S</i>. Typhimurium D23580 (ST313) were used as controls for the assay. Percent survival was expressed as the number of intracellular bacteria at 24 h p.i. divided by the number of intracellular bacteria at 0 h p.i. times 100. Results are expressed as mean ± SD from at least 3 independent experiments. ** represents P <0.01.