Innate resistance of mice to Salmonella typhi infection.

The basis for the natural resistance of mice to Salmonella typhi was examined. In contrast to Salmonella typhimurium, the virulence of S. typhi for mice was independent of the mouse strain and was not affected by inactivation of murine macrophages with silica. However, mice were more susceptible to S. typhi when given iron alone or iron and an iron chelator. The results suggest that the failure of S. typhi to undergo net growth in murine tissues reflects an inability of the bacterium to multiply rather than rapid killing by resident macrophages.