Figure 1.

Colonization of mouse organs by a S. typhimurium Dam⁻ mutant. Groups of 8-wk-old BALB/c mice were infected orally with 8.8 × 10⁸ colony-forming units (cfu) of the strain SV1610 (Dam⁻) [black histograms] or 7.5 × 10⁵ cfu of strain SL1344 (wild type) [white histograms]. Another group of mice were infected intraperitoneally with 1.5 × 10⁵ cfu of SV1610 (Dam⁻) [grey histograms]. At the times indicated, lymph nodes (A), liver (B), and spleen (C) were removed from two infected mice, and viable bacteria were determined by plating. At 8 days after infection, all the wild-type infected mice showed clear evidence of disease.