Molecular epidemiology of verotoxigenic Escherichia coli O157:H7

Verotoxigenic E. coli (VTEC) O157:H7 is a zoonotic disease agent with asymptomatic ruminants such as cattle and sheep as reservoir hosts. Infection in humans can cause bloody diarrhoea with occasionally fatal complications such as haemolytic-uraemic syndrome (HUS), particularly in children. In this thesis, the genetic variation among representative sets of O157:H7 isolates from Swedish cattle, sheep and human clinical cases is studied to find markers to predict the relative pathogenicity of different genotypes, and to improve methods for tracing spread of the bacteria. The results show that the same types occur in cattle, sheep and human patients infected within the country. However, certain types are common among ruminants while extremely rare among patient isolates, while others are overrepresented among patients. Better molecular tracing tools together with interventions targeted against highly pathogenic types of O157:H7 will allow more efficient and cost-effective efforts to reduce the burden of disease caused by VTEC O157:H7