Abscess induction by S. aureus. (A) Rats were challenged with live or formalin-killed S. aureus Reynolds cells. (B) Dose titration curves for serotype 5 strain Reynolds, the acapsular mutant JL243, and serotype 8 strain PS80. The calculated AD50 values for three strains were 60, 1.2 × 103, and 51 cfu, respectively.