Figure 10. l-serine catabolism provides a greater fitness advantage to P. mirabilis within the catheterized urinary tract than d-serine catabolism.

Wild-type P. mirabilis, the l-serine catabolism mutant (ΔsdaAB) and the triple mutant (ΔsdaABΔdsdA) were cultured in LB broth overnight, washed once in PBS, and adjusted to 2×10⁶ CFU/ml. (A) Female CBA/J mice were transurethrally inoculated with 50 μl containing 1×10⁵ CFU of either WT (n=12), ΔsdaAB (n=11), or ΔsdaABΔdsdA (n=10), and a 4 mm segment of silicone catheter tubing was advanced into the bladder during inoculation. Mice were euthanized 96 hours post-inoculation (hpi), and bacterial burden was determined in the urine, bladder, kidneys, and spleen. Each symbol represents the Log₁₀ CFU per milliliter of urine or gram of tissue from an individual mouse, gray bars represent the median, and the dashed line indicates the limit of detection. ***P<0.01 by nonparametric Mann-Whitney test. (B-D) CBA/J mice were inoculated as above with the following 50:50 mixtures and euthanized at the indicated time points: (B) WT and ΔsdaAB (n=10, 96 hpi); (C) WT and ΔsdaABΔdsdA (n=10, 48 hpi); and (D) ΔdsdA and ΔsdaAB (n=10, 96 hpi). Each symbol represents the Log₁₀ CFU per milliliter of urine or gram of tissue from an individual mouse, with CFUs of each strain recovered from an individual mouse connected by a black line. A competitive index was also calculated for each co-challenge, in which each symbol represents the Log₁₀ CI for an individual mouse, error bars represent the median, and the dashed line indicates Log₁₀ CI=0 (the expected value if the ratio of the indicated strains is 1:1). *P<0.05, **P<0.01 by Wilcoxon signed-rank test.