FIG 3.

Bacterial burden and pathology scoring in female C3H/HeJ mice infected with hypovirulent mutants of C. rodentium. Susceptible mice were orally gavaged with 2 × 10⁸ to 3 × 10⁸ CFU of C. rodentium wild type or a TCS deletion strain, and fecal burden of C. rodentium was assessed at days 3 (A), 6 (B), and 9 (C) postinfection by plating on MacConkey agar and counting CFU. At day 9, due to significant illness manifestation, in the absence of fecal matter, colon was homogenized and plated. By day 9 postinfection, several of the mice infected with the wild type and the less attenuated TCS deletion strains had succumbed to infection, leading to fewer samples analyzed at this time point in those groups. Dotted lines indicate the limit of detection of the assay. The data are pooled from two experiments with 4 to 5 mice per group per experiment. A Mann-Whitney test was used to determine statistical significance (***, P < 0.001; **, P < 0.01; *, P < 0.05). (D) The last 0.5 cm of the colon of infected mice was stained by hematoxylin and eosin, and histological scoring was performed in a blinded fashion by a board-certified veterinary pathologist, as described in reference 55. An unpaired t test was used to determine statistical significance between each TCS deletion strain and the wild-type strain (*, P < 0.05).