FIG 4.

S. aureus lacking all four Msr enzymes is attenuated for dissemination to the spleen in a murine model of intraperitoneal infection. Female 8-week-old BALB/cJ mice were infected intraperitoneally with USA300 wild-type or Δmsr strains. After 4 days of monitoring, the heart, kidneys, liver (A), lungs (B), and spleen (C) were harvested, homogenized, and dilution plated on solid medium to enumerate viable bacteria. No viable bacteria were detected in the heart or kidneys. Gray symbols indicate bacterial burdens below the limit of detection, and so the limit of detection was used for statistical analyses. Data are means ± standard deviations, and P values were calculated by Mann-Whitney test.