Abscess induction in mice. Abscess formation was induced when 0.5 ml of bacterial cell suspension (3 × 107 CFU/ml) of strain 17 was injected into the inguinal area of a mouse (left panels). In contrast, the subcutaneous injection of strain 17-2 (0.5 ml at a concentration of 107 and 108 CFU/ml) failed to induce an abscess in mice (right panels). Relatively small abscesses were induced when a higher cell concentration of strain 17-2 (109 CFU/ml) was injected (right bottom panel). The data are from one of three independent experiments.