ESCHERICHIA-COLI O157-H7

Escherichia coli O157 was first identified as a human pathogen in 1982 . One of several Shiga toxin-producing serotypes known to cause human illness, the organism probably evolved through horizontal acquisition of genes for Shiga toxins and other virulence factors. E coli O157 is found regularly in the faeces of healthy cattle, and is transmitted to humans through contaminated food, water, and direct contact with infe cted people or animals. Human infection is associated with a wide rang e of clinical illness, including asymptomatic shedding, non-bloody dia rrhoea, haemorrhagic colitis, haemolytic uraemic syndrome, and death. Since laboratory practices vary, physicians need to know whether labor atories in their area routinely test for E coli O157 in stool specimen s. Treatment with antimicrobial agents remains controversial: some stu dies suggest that treatment may precipitate haemolytic uraemic syndrom e, and other studies suggest no effect or even a protective effect. Ph ysicians can help to prevent E coli O157 infections by counselling pat ients about the hazards of consuming undercooked ground meat or unpast eurised milk products and juices, and about the importance of handwash ing to prevent the spread of diarrhoeal illness, and by informing publ ic health authorities when they see unusual numbers of cases of bloody diarrhoea or haemolytic uraemic syndrome.