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

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 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 Stx2 ؉ 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.Enterohemorrhagic Escherichia coli (EHEC), a food-borne bacterial pathogen of humans, is a normal inhabitant of the ruminant intestine. This organism is most often transmitted to humans in undercooked meat, but it has also caused outbreaks associated with contaminated vegetables (5, 28), fruit juices (6), and drinking water (41). The disease manifestations include watery or bloody diarrhea and can be severe enough to cause hospitalization and even death (18). In addition, some affected children (and rarely adults) develop hemolytic-uremic syndrome (HUS), a rapidly progressive, often fatal form of renal failure that is attributed to expression of Shiga toxins (Stx) by pathogenic bacteria (2, 18). HUS is defined by a triad of symptoms that includes hemolysis, uremia, and thrombocytopenia. It is a rare complication of disease due to EHEC, but its importance is amplified by its severity, tendency to affect young children, and the absence of any specific treatment or preventative measure. Thus, the significance of disease due to EHEC is derived from its food-borne nature and its potentially severe consequences.Both HUS and hemorrhagic colitis caused by EHEC have been attributed to the production of Stx by pathogenic bacteria (2, 50) referred to as Stx-producing E. coli (STEC). The Stxs are macromolecular cytotoxins that are phage encode...

Safety and Biocompatibility of Carbohydrate-Functionalized Polyanhydride Nanoparticles

“…The levels of BUN, urine creatinine, and total protein/creatinine ratio in mice receiving the particle treatments were not significantly different from the levels in animals receiving the saline. Even though BUN content level was lower than the reference values provided, the values were consistent with previously reported data in Swiss Webster mice (43). Creatinine and total protein-tocreatinine ratio levels in mice administered with the particles were no different than in animals receiving the saline control and consistent with the amounts reported in urine from mice of this lineage (35,41).…”

“…Even though BUN levels were slightly lower than the reference values, there were no significant differences between the saline and particle groups. Variations in normal BUN levels have been previously reported to be mouse strain-dependent (34,35,43).…”

Shiga Toxin Subtypes Display Dramatic Differences in Potency

“…The role of apoptosis in Stx-mediated disease is also unclear. Several studies utilizing mouse models have observed apoptosis in renal cells following treatment with Stx (23,42,47), while other studies have observed necrosis (10,29,37,46,58,60).…”

In Vitro and In Vivo Model Systems for Studying Enteropathogenic Escherichia coli Infections

“…Bioluminescent strains of EPEC and EHEC show tight association of the bacteria with cecal and colonic tissues of streptomycintreated mice accompanied by mild inflammation Rhee et al 2011) and, in the case of EHEC, microvilli effacement . Germ-free mice have been used to study toxin suppression and production of other virulence factors by EHEC as well as the use of probiotics for protection against colonization and EHEC-mediated disease (Takahashi et al 2004;Eaton et al 2008Eaton et al , 2011. Alternatively, human xenografts of the small and large intestine in severe combined immunodeficiency mice have recently been proposed as a model to evaluate T3S effector function in native tissue and to investigate tissue tropism (Golan et al 2011).…”