A SPI-1 (<i>invA</i>) mutant of 14028s does not cause diarrhea despite being able to invade the colons of BALB/c.D2^Nramp1 congenic mice.

<p>A. Diarrhea scores (mean±1SEM) for mice infected with 14028s (WT) or the <i>invA</i> mutant, 8 or 9 days after infection. The numbers of mice in each group are shown above the bars. The difference in means (Mann Whitney U test) was significant (P<0.05). B. Mean water content of feces from uninfected (control), 14028a-infected (WT), and <i>invA</i>-infected mice 8 days after infection. There was no significant difference between the % of water in feces from <i>invA</i>-infected and from control mice. The % of water in feces from WT–infected mice was significantly greater than the % in the other two groups. C. CFU from feces and three segments of the colon 8 days after infection with either WT or <i>invA</i>- <i>Salmonella</i>. Each symbol represents one mouse and the horizontal bars show the geometric means. P values were calculated using the Mann-Whitney U test.