Fig 6.

Colonization of BALB/c mice by wild-type STEC O5:NM strain 88-0643 and its isogenic Δure gene cluster deletion mutant in competition experiments. Mice were inoculated intragastrically with 10¹⁰ CFU of a 1:1 mixture of the wild-type and Δure mutant strains, and feces samples were collected daily for 7 days postinfection. The colonization levels of the wild-type strain and Δure mutant were determined by selective plating of the feces. (A) The results are plotted as means and standard errors of the mean for 17 mice. The level of colonization by the wild-type strain was significantly higher than that by the Δure mutant strain for each of the 7 days following inoculation, as determined using the Wilcoxon signed-rank test (P = 0.015 for day 2 and P < 0.0006 for all other days). (B) The competitive index was calculated as the level of colonization of the wild-type strain divided by the level of colonization of the Δure mutant strain for each mouse. Mice for which colonization by the Δure mutant could no longer be detected are not included in this analysis. The competitive index is plotted for each of the 7 days following inoculation on day zero, and the horizontal bars represent the median values. For each day postinfection, the median was significantly different from a value of 1, with P values calculated using the Wilcoxon signed-rank test and reported in Table 3.