E.coli O157:H7

The serious nature of the symptoms of haemorrhagic colitis and HUS and the apparent low infectious dose (<100 cells) of E.coli O157:H7 places this food borne pathogen a most serious of known food borne pathogens. Persuasive evidence suggests that healthy cattle are a reservoir of O157 and they can enter the food chain to provide a source of exposure for humans. A possible route of transmission of O157 VTEC may involve infections initially in calves that shed their organism into faecal slurry that may be used on grazing grass. This provides potential for infection of other animals from which the organism may contaminate milk or carcasses at slaughter. Possible sources of VTEC in healthy animals other E.coli O157:H7 than cattle and a wider range of foodstuffs require further investigation. Many features of E.coli O157:H7 strains remain poorly understood. It includes: (i) Role of virulent genes in the animal, (ii) Mechanism of evolution of the organism, (iii) The progress of individual cases of E.coli O157:H7 infection, and (iv) The difference in incidence of infection in different geographical areas. [Veterinary World 2008; 1(3.000): 83-87]