Inoculation strategy affects successful colonization of C57BL/6 mice.

<p>(A) Prior to inoculation, mice were treated as indicated on the X axis (S-1 mg/ml streptomycin in water; F-restriction of food overnight; A-anesthesia with ketamine-xylazine intraperitoneally at time of inoculation; B-intragastric delivery of sodium bicarbonate, and L-inoculation of bacteria in the logarithmic phase of growth. Control mice (+all) were infected using all five parameters. Mice were then inoculated with 1−5×10⁷ CFU <i>V. cholerae</i> El Tor O1 strain P27459 and colonization of the small intestine assessed after 20 hr. Data are pooled from 3 experiments so the input variation between experiments was normalized by dividing the recovered CFU by the input CFU and data are thereby plotted as a log colonization index with dashed line at 0 indicating that CFU recovered was identical to the input CFU (<i>i</i>). Markers above the dashed line are indicative of growth in the small intestine while markers below indicate clearance. Values below the solid line (<i>d.l.</i>) were below the detection limit of 500 CFU in the small intestine. The number of mice that cleared <i>V. cholerae</i> from the small intestine (<i>n</i>) over the total of mice in the group (<i>n</i>°) is also indicated. The experiment in panel B was performed as above except an additional parameter of anesthesia with inhaled isoflurane (+I) was added and data are pooled from two experiments. Significant and borderline P values are shown compared to control for survival (calculated by a χ2 test) and for colonization (calculated by a Mann-Whitney non-parametric t-test comparing medians).