Fig. 3.

Virulence of S. aureus lgt and lsp mutants. Six-week-old C57BL/6 mice were infected i.v. with 5 × 10⁶ cfu for each strain. (A) Mice were monitored for the development of acute, lethal disease for 5 days upon infection of wild-type (WT) Newman, the lgt mutant strain, or lgt mutant carrying empty vector or complementing plasmid pLgt. (B) Kidneys were harvested from mice infected for 4 days with mutant strain lgt carrying the empty vector or infected for 5 days with WT Newman or complemented mutant strain lgt/pLgt. The kidneys were photographed to visualize the formation of abscesses. (C) In a separate experiment, animals infected with either WT or lgt mutant staphylococci and still alive 2 days after infection were killed. Kidneys and liver were removed and homogenized. Viable bacteria were counted after dilution and colony formation on tryptic soy agar. Statistical significance was examined with Student’s t test, and P values were recorded. The limit of detection (dashed line) was determined to be 100 cfu (10²). (D) Dissemination to organs of WT or lsp mutant staphylococci 4 days after infection.