FIG. 3.

The effect of oral bacterial treatment on the total number of fecal STEC bacteria. The number of STEC CFU/g feces was determined by colony hybridization and PCR. Four experimental groups are shown that were treated with biweekly oral doses of 5 × 10¹⁰ CFU bacteria/animal. Two groups received STEC starting 2 weeks before BLV challenge (pre & post BLV STEC group) (A) or starting 24 h post-BLV challenge (post BLV STEC group) (B) and continuing for 16 weeks post-BLV challenge. Two groups received E. coli K-12 starting at week −2. The infection control group received BLV (BLV no STEC) (C), and the healthy control group was not challenged with BLV (no BLV) (D). Within each group, two subgroups of three (solid circles) or two (empty circles) animals were identified that had similar STEC counts (animal identifiers in key). The samples that were STEC positive by PCR but had no hybridization counts were assigned a value of 10 CFU/g feces. A solid arrow indicates commencement of biweekly STEC treatment, and a stippled arrow indicates the single injection of sheep with BLV. A horizontal solid line at log 4 separates CFU counts considered high (above log 4) and those considered low (below log 4).