FIG 7 .

Virulence of ΔzntA ΔzitB mutant S. Typhimurium is attenuated in NO·-producing mice. Solid lines represent the median competitive index (CI) for each organ. The dotted line represents the expected CI if neither strain has a competitive advantage. (A) In wild-type C3H/HeOuJ mice, a ΔzntA ΔzitB mutant has a significant competitive disadvantage compared to wild type (P = 0.002 by Wilcoxon signed-rank test to a hypothetical median of 1 for both spleen and liver). (B) In C3H/HeOuJ mice that cannot produce NO· due to treatment with 500 µg ml⁻¹ l-N₆-(1-iminoethyl)lysine dihydrochloride (l-NIL), the mutant no longer has a statistically significant disadvantage compared to wild type, and the CIs are significantly different (*, P = 0.007 for spleen and P < 0.001 for liver by Mann-Whitney test) from the CI in untreated mice. A total of 10 animals were tested for each condition. Data points at a CI of 0.01 were at the limit of detection for the assay.