Contents Introduction History Characteristics Mechanism of action Factors influencing growth Toxins Symptoms Transmission Complications Epidemics Food association Diagnosis Disinfectants Therapies Vaccination  Preventions  References Enterohemorrhagic Escherichia coli Introduction E. coli is a gram-negative bacterium present in the form of rods (bacilli) in the Enterobacteriaceae. Mostly E.coli are normal commensals of the intestine, so it is necessary to isolate pathogenic strains based on virulence factors, such as toxins. The EHEC group produces Shiga-like toxins (stx), enterohemolysin, and intima adhesion factor (Intimin). Serotypes E.coli serotypes based on O (somatic polysaccharides), H (flagellar) and K (capsular) antigens. EHEC serotypes include E.coli O157:H7 and others O26, O103, O111, O145. Research studies show only a small no. of E.coli are enough to cause an infection equal to 10-100 microbes. History of EHEC In 1982, E.coli O157:H7 was first identified as a cause of bloody diarrhea from eating undercooked or contaminated raw hamburger. The infection was first recognized by the CDC separates two epidemics in Oregon and Michigan by eating hamburgers at national chain restaurants. Patients have experienced hemorrhagic colitis (inflammation and bleeding of the colon) due to E.coli O157:H7 called hamburger disease.Characteristics• E.coli O157:H7 is a major disease serotype associated with hemorrhagic colitis• Does not ferment sorbitol and has glucuronidase activity compared to other E.coli strains.• Grows rapidly at 30-42°C, poor growth at 44-45°C, and shows no growth at 10 °C.• Resists pH 4.5…… half paper……., and Ammar, MS1993. Survival and growth of Escherichia coli O157:H7 on salads. Appl. Environment. Microbiol.59:1999–2006.Ahmed, N.M., Conner, D.E. and Huffman, D.L. 1995.Heat resistance of Escherichia coliO157:H7 in meat and poultry influenced by product composition. J.Food Sci.60:606–610.Doyle, M.P., Escherichia coli 0157:H7 and its significance in foods, cadence. J. Food Microbiol., 12,289,1991. Donnenberg, MS and Whittarn, TS, Pathogenesis and evolution of virulence in enteropathogenic and enterohemorrhagic Escherichia coli, J. Clin. lnv., 107(5),539, 200l.Anonymous, FSIS background update on Escherichia coli: E. coli 0157:H7, Office of Media Relations, Food Service and Inspection Service, USDA, January 1993. MICROBIOLOGY FUNDAMENTAL FOOD FOURTH EDITION