While both E. coli and P. mirabilis required TCA cycle reactions for fitness in vivo, sdhB was required for fitness only during cystitis (bladder CFU) in E. coli (Fig. 4A) and only during pyelonephritis (kidney CFU) in P. mirabilis (Fig. 4B) (P>0.050). This evidence concerns the gene SDHB and cystitis.