FIG. 3.

Shedding levels over time of E. coli O157:H7 wild-type (□) and GadC⁻ (▪) (A) or wild-type (□) and AdiA⁻ (▪) strains (B). Calves were inoculated with 10¹⁰ total CFU containing equal numbers of wild-type and mutant strains on day 0. Fecal samples were cultured daily beginning 1 day postinoculation. Colony counts are displayed as the means for four calves. Bars indicate standard deviation of mean log₁₀ CFU/gram values. Asterisks indicate significant difference in shedding between wild-type and mutant strains at P < 0.05 using repeated measures of analysis of variance. Specimens containing <10³ CFU/g of feces were below the level needed for accurate enumeration.