FIG. 3.

Histopathological signs of arthritis in mice 14 days after inoculation with 3 × 10⁶ to 4 × 10⁶ CFU of S. aureus wild-type strain 8325-4 (rsbU mutant), SH1000 (rsbU⁺), or MJH502 (sigB mutant). Data from two experiments are pooled (n = 20, 1,8, and 19, respectively). A scoring system based on the degree of synovial hypertrophy and degradation of cartilage and/or bone was used: 1, mild synovial hypertrophy and joint damage; 2, moderate damage; 3, severe damage. Data are medians (bold line) and IQRs for each group of mice. Comparisons with strain SH1000 were made by using the Mann-Whitney U test.