Fig. 2.

OI-51 contributes to ruminant colonization. Six animals were orally dosed with both wild-type (WT) (TUV93-0) and ΔOI-51 EHEC O157:H7 strains as described in Experimental procedures. A. Levels of both strains were determined daily from faecal samples. ‘PosE’ are samples that were positive for the strain following broth enrichment; ‘NegE’ samples were negative following broth enrichment. B. The cumulative shedding levels for each animal and strain were estimated for colonized animals from day 5 onwards to avoid inoculum effects. One animal was excluded from the analysis that was not properly colonized by either strain (< 20 cfu per gram of faeces). The different symbols represent individual animals and allow direct comparison of the two strains in each animal. The right-hand panel of the graph shows the percentage mean decrease of the mutant strain by comparison with the WT. The difference in cumulative shedding levels in the five colonized animals was assessed by a one-sample t-test compared to a null hypothesis of 0 change. The data were log10 transformed data to normalize the values, and the difference was statistically significant (P = 0.006).