FIG. 1.

Representative examples of the gross pathology of Peyer’s patch and mucosa of the terminal ileum of calves inoculated orally with 10¹⁰ CFU of different S. typhimurium strains. (A) Severe acute fibrinopurulent necrotizing enteritis with segmental or continuous pseudomembrane formation of calves inoculated with wild type (IR715), strain STN272 (spvR), or strain SVM255 (sigD). (B) Moderate to marked subacute fibrinopurulent enteritis often confined to Peyer’s patches of calves inoculated with STN119 (spiB) or STN166 (rfaJ). (C) Normal Peyer’s patch and ileal mucosa of calves inoculated with STN61 (hilA), STN162 (prgH), or CL1509 (aroA) or of uninoculated controls. Bar = 1 cm.