Figure 7. Hfq is required for virulence of Y. enterocolitica in Balb/c mice.

Balb/c mice (n = 9 per group) were infected intraperitoneally with 4 × 10³ CFUs of Y. enterocolitica. (a) Mice body weight during infection with parent strain WA-314 (white bars) and hfq-negative strain SOR4 (grey bars). Median weight is indicated by a horizontal line, the boxes show the 25^th and 75^th percentile and the whiskers show the range. Significance was calculated with Student’s unpaired t-test between day 0 and the subsequent time points (*P < 0.05, ***P < 0.001). (b) Number of CFUs recovered from liver and spleen after four days of infection with parent (black circles) and hfq mutant (black squares). The limit of detection is indicated by a dashed line, and symbols below represent mice that did not have detectable numbers of bacteria. A solid line represents the mean of CFUs recovered. Significance was calculated using the unpaired t test with Welch’s correction (**P < 0.005, ***P < 0.0005).