A rabbit model of diarrhea due to invasive Escherichia coli

A nonpiliated strain of invasive Escherichia coli of human origin (HInvEC) was given to rabbits (weight, 0.7-1.1 kg) in doses ranging from 1.5 X 10(8) to 2.5 X 10(10) bacteria. E. coli strain HInvEC colonized the ileum, cecum, and colon in large numbers for one to three days and produced diarrhea in 91 ((58%) of the 156 rabbits. A dose of 2.5 X 10(10) bacteria reliably and repeatedly elicited diarrheal disease in 80% of the animals. The acute pathohistology as determined by light microscopy, transmission electron microscopy, and immune fluorescent microscopy was manifest in the distal ileum, cecum, and colon. Prominent findings included mucosal ulcers, bacterial invasion of the lamina propria, and a polymorphonuclear infiltrate in the lamina propria. Diarrhea due to strain HInvEC was followed by a rise in the titer of serum antibody to O antigen of E. coli.