FIG 3.

The role of type III secretion in abscess formation. C57BL/6J mice were infected in the subcutaneous space with either PA99 or PA99null. (A) The abscess size was measured daily over a 2-week period. Data are the mean abscess sizes for 5 mice per group, and error bars represent standard errors of the means. (B) Abscess tissues were harvested at 24 h postinfection, and cross sections of the abscesses were stained with H&E. Arrows, the abscess formed under the skin. (C) Abscess tissues were harvested by punch biopsy, and bacterial loads were determined by plating serial dilutions of tissue homogenates. Each symbol represents the abscess from a single mouse. Data are means plus standard deviations and were analyzed using an unpaired t test. Experiments used four mice per group and were performed at least three times. *, P < 0.05. (D) Abscess tissues were harvested at 24 h postinfection and homogenized. IL-1β levels were determined by ELISA. Data are means plus standard errors of the means and were analyzed using unpaired t tests. *, P < 0.05; **, P < 0.01. Experiments were done on three mice per group and were performed at least twice. D.P.I., days postinfection.