Pathogenesis of renal disease due to enterohemorrhagic Escherichia coli in germ-free mice

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 that were 3 days to 12 weeks old were orally inoculated with 1 of 10 EHEC strains or derivatives of two of these strains with Stx2 deleted. All inoculated mice became infected regardless of the inoculum dose. All bacterial strains colonized the intestines, reaching levels of 10(9) to 10(12) CFU/g of feces by 4 days after inoculation. Seven of the 10 wild-type strains caused disease. However, the two Stx2 deletion mutants, unlike the Stx(2+) parental strains, did not cause disease. The clinical signs of disease in mice included lethargy, dehydration, polyuria, polydypsia, and death. Postmortem 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 in the colon. Other lesions included progressive renal tubular necrosis, glomerular fibrin thrombosis, and red blood cell sludging. The severity of disease varied according to the bacterial strain and age, but not sex, of the 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. The disease in mice was Stx2 and bacterial strain dependent. This animal model should be a useful tool for studying the pathogenesis of renal disease secondary to EHEC infection.