ABSTRACT
Group of Organisms................................................................................... 31 2.2 EHEC-Mediated Hemorrhagic Colitis..................................................... 33 2.3 Role of Shiga Toxins in EHEC Pathogenesis ......................................... 35 2.4 Stx2 Binding to Human Serum Amyloid P Component...................... 36 2.5 Gb3-Independent Stx1 and Stx2 Binding to Human Neutrophils ..... 39 2.6 Effects of Stx Binding on Neutrophil Function ..................................... 42 2.7 Treatment and Vaccination Strategies..................................................... 42 2.8 Concluding Remarks.................................................................................. 43 References ............................................................................................................. 44
The enterohemorrhagic Escherichia coli (E. coli) (EHEC) represent a subgroup of the enterovirulent bacteria known as Shiga toxin-producing E. coli or STEC.1 What distinguishes the EHEC from other STEC is their etiologic association with two clinical conditions: hemorrhagic colitis (HC), and, occasionally, hemolytic uremic syndrome (HUS), in humans.1,2 Although E. coli serotype O157:H7 causes the majority of cases of HC and HUS in North America and other parts of the developed World, numerous other less prevalent EHEC serotypes have been isolated from subjects afflicted by these pathogens.3-5
The clinical symptoms of HC include diarrhea, often but not always bloody, and abdominal pain. Fever is usually absent, or if present, is typically of a low grade. HUS, when it occurs, comprises a triad of clinical features, including hemolytic anemia, thrombocytopenia, and acute renal failure. The illness is associated with consuming EHEC-contaminated ground beef (hence its popular name, ‘‘hamburger disease’’) which has not been thoroughly cooked, or with ingesting untreated well water, unpasteurized milk, products produced from the same, or fruits and vegetables which have been washed in EHEC-contaminated water.6-12
Cattle represent a significant reservoir for these organisms13-16 and the primary risk groups include young children and elderly individuals.17-22
Additional risk factors include the proximity of one’s dwelling to intensive agricultural operations involving cattle.23,24,25 Because of the low infectious dose, person-to-person spread has also been documented in both sporadic and outbreak situations.26
