FIG 1.

Flagellin protects against intestinal infection (but not systemic infection) by Y. pseudotuberculosis. Female BALB/c mice were treated intraperitoneally with flagellin (5 μg) or LPS (5 μg) in phosphate-buffered saline (PBS) or with PBS alone. The animals were challenged 30 min later with an intragastric inoculation of 5 × 10⁸ CFU of Y. pseudotuberculosis (A, C, and D) or an intravenous injection of 10³ CFU of Y. pseudotuberculosis (B). (A) The survival of mice (n = 9) after an oral challenge was monitored for 14 days. One of three representative survival experiments is shown here. Statistical significance was determined using a log rank test compared to the untreated mice (***, P < 0.001). (B) The survival of mice (n = 10) after an intravenous challenge was monitored for 7 days. Bacterial counts in the stools (C) and the spleen (D) were determined 72 h after the oral challenge. CFU counts for individual mice (n = 7 to 14) are shown. The solid line corresponds to the median value, and the dashed line represents the detection threshold. Data from flagellin-treated and untreated mice were compared in a Mann-Whitney test (*, P < 0.05; ***, P < 0.001).