Critical roles for stx2, eae, and tir in enterohemorrhagic Escherichia coli-induced diarrhea and intestinal inflammation in infant rabbits.
Enterohemorrhagic Escherichia coli (EHEC) is a group of food-borne pathogens that can cause diarrhea, colitis, and the hemolytic uremic syndrome (HUS). The importance of several of the proposed EHEC virulence factors lacks experimental verification in animal models. The limitations of current animal models led us to reexamine the infant rabbit model for the study of EHEC pathogenicity. Here, we report that intragastric inoculation of a Shiga toxin 2 (Stx2)-producing E. coli O157:H7 clinical isolate into infant rabbits led to severe diarrhea and intestinal inflammation but no signs of HUS. We constructed a set of isogenic derivatives of this isolate with deletions in several putative virulence genes, including stx(2), eae, tir, and ehxA, to investigate the contribution of individual virulence factors to EHEC pathogenicity. stx(2) increased the severity and duration of EHEC-induced diarrhea. Furthermore, although stx(2) had no role in EHEC intestinal colonization nor was it required for EHEC-induced inflammation, stx(2) altered how the host responded to EHEC infection by promoting heterophilic infiltration of the colonic epithelium and lamina propria. Intragastric inoculation of purified Stx2 also induced inflammation and diarrhea in this model. Diarrhea and intestinal inflammation were also dependent on EHEC colonization, as EHEC derivatives with deletions in eae and tir did not colonize, form attaching and effacing lesions, or develop clinical signs of disease. Our studies indicate that infant rabbits are a useful model for investigation of the intestinal stage of EHEC pathogenesis and suggest that Shiga toxin may play a critical role in causing diarrhea and inflammation in patients infected with EHEC.
Ritchie
Jennifer M
JM
Division of Geographic Medicine and Infectious Diseases, Tufts-New England Medical Center, and Howard Hughes Medical Institute, Boston, Massachusetts 02111, USA.
Thorpe
Cheleste M
CM
Rogers
Arlin B
AB
Waldor
Matthew K
MK
D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D003967:Diarrhea / Q000276:immunology / Q000382:microbiology / Q000503:physiopathology*; D004195:Disease Models, Animal; D004927:Escherichia coli Infections / Q000276:immunology / Q000382:microbiology / Q000503:physiopathology; D019453:Escherichia coli O157 / Q000276:immunology / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000382:microbiology / Q000503:physiopathology*; D007422:Intestines / Q000382:microbiology; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D022641:Shiga Toxin 2 / Q000235:genetics / Q000378:metabolism; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
D018829:Adhesins, Bacterial; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D011956:Receptors, Cell Surface; D022641:Shiga Toxin 2; C109287:Tir protein, E coli; D037521:Virulence Factors; C073819:eaeA protein, E coli