Evaluation of E. coli O157:H7 tropisms to lymphoid (A) and non-lymphoid (B) regions of the GIT in young lambs orally inoculated with approximately 1 × 10¹⁰ CFU, as determined by bacterial enumeration after necropsy. All data points on or above the dotted line were obtained after direct plating. All data points below the dotted line were obtained after enrichment of faecal samples negative for growth after direct plating. These enrichment data points are only nominal and could represent any value between 1 and 99 CFU/g faeces⁻¹. Samples where no E. coli O157:H7 growth was detected after enrichment are not shown. N.B.: Non-lymphoid ileum was actually sampled from a part of the ileum where less dense lymphoid tissue reside, as the majority of ovine ileum exhibits lymphoid rich sites.