Fig 7.
Effect of regR on virulence of REPEC strain E22. Six infant rabbits were inoculated with 5 × 105 CFU of wild-type E22 or 8 × 105 CFU of its isogenic regR mutant (E22 ΔregR). When some rabbits in a group were euthanized, due to loss of body weight of greater than 15% or the presence of severe diarrhea, the surviving numbers of rabbits are shown adjacent to the data points. (A) Colonization of rabbits by REPEC strain E22 and the regR mutant as measured by quantitative culture of rectal swabs. Data are the geometric mean CFU per swab (***, P < 0.0005; **, P < 0.005; and *, P < 0.05). The detection limit of the culture method is indicated by the horizontal line. (B) Body weight of rabbits. Values are the mean (± SD) for each group expressed as a percentage of the weight on the day of infection (day zero).