FIG. 1.

Course of fecal excretion of E. coli O157:H7 eae and tir mutants in 14-day-old calves (A) and six-week-old lambs (B). The level of colonization is indicated by the mean log-transformed viable count (CFU/g) of E. coli O157:H7 in fecal samples taken twice daily for 12 days (A) or at intervals for 27 days (B). The data for the 85-170 Nal^r Δtir single mutant have been described previously (16) and are shown for the purpose of comparison. The error bars indicate the standard errors of the means.