FIG 6.

YdgH deletion results in conserved phenotypes in Escherichia coli O157:H7 EDL933 and Enterobacter cloacae ATCC 13047. (A) The YdgH phylogeny was constructed based on amino acid substitutions by using the maximum-likelihood method and the JTT matrix-based model in MEGA X. The relevant higher-order families are indicated. (B) All 3 mutants have decreased susceptibility to ceftriaxone (E. cloacae has high intrinsic resistance to cefoxitin, so ceftriaxone was chosen), as well as increased susceptibility to benzethonium chloride. Growth of the E. cloacae ΔydgH mutant was decreased in SDS, although growth of E. coli O157:H7 was not. Due to inherent differences in Wt susceptibility, drug concentrations differed considerably between isolates and were as follows: ceftriaxone, 4 μg/ml for E. cloacae, 0.04 μg/ml for E. coli O157:H7, and 0.06 μg/ml for S. marcescens; benzethonium chloride (BTC), 10 μg/ml for E. cloacae, 18 μg/ml for E. coli O157:H7, and 52 μg/ml for S. marcescens); SDS, 0.8% for E. cloacae, 0.13% for E. coli O157:H7, and 5% for S. marcescens. *, P ≤ 0.05; **, P ≤ 0.01; unpaired two-tailed t test, unadjusted.