The Pathogenesis of Renal Disease Due to Enterohemorrhagic Escherichia coli in Germ Free Mice

Department of Laboratory Animal Medicine, University of Michigan, Ann Arbor MI 48109; Department of Microbiology and Immunology, University of Michigan, Ann Arbor MI 48109; National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824-131

	Abstract

Enterohemorrhagic Escherichia coli (EHEC) is a food-borne pathogen that causes hemorrhagic colitis and acute renal failure. We used a germ-free mouse model to investigate the role of host factors, Shiga Toxin 2 (Stx2), and bacterial strain in disease due to EHEC. Germ-free male and female Swiss-Webster mice, 3 days – 12 weeks of age, were orally inoculated with one of ten EHEC strains or derivatives of two of these strains with Stx2 deleted. All inoculated mice became infected regardless of inoculum dose. All bacterial strains colonized the intestines, reaching 10⁹ – 10¹² cfu/g of feces by 4 days after inoculation. Seven of the ten wild-type strains caused disease. However, the two Stx2 deletion mutants, unlike their Stx2+ parental strains, did not. Clinical signs of disease in mice included lethargy, dehydration, polyuria, polydypsia, and death. Post mortem examination of affected mice revealed dehydration and luminal cecal fluid accumulation. Histologic examination revealed close adherence of bacteria to the intestinal epithelium in the ileum and cecum but not the colon. Other lesions included progressive renal tubular necrosis, and glomerular fibrin thrombosis and red blood cell sludging. Severity of disease varied according to bacterial strain and age but not sex of host. This study demonstrated that EHEC colonizes germ free mice in large numbers, adheres to the intestinal epithelium, and causes luminal cecal fluid accumulation and progressive renal failure. Disease in mice was Stx2- and bacterial strain-dependent. This animal model will be a useful tool in studying the pathogenesis of renal disease secondary to EHEC infection.