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Review of past and current research on Verocytotoxin producing Escherichia coli (VTEC) in relation to public health protection

Project Code: B11010

31/08/2006

Campden BRI
Baylis, C ;
HPA Colindale
Smith, H;
HPA Manchester
Bolton, E;
University of Manchester
O'Brien, S

Escherichia coli is a common bacterium found in the intestines of many animals including man. Most strains of E. coli are harmless although some strains are capable of causing diarrhoeal disease in humans and some can be responsible for more severe infections and clinical complications. One group of pathogenic E. coli is the Verocytotoxin-producing Escherichia coli (VTEC), which comprises a large group of E. coli serotypes capable of producing Vero cytotoxins (VT), of which there are 2 main types, VT1 and VT2, but also a number of VT2 variants. These toxins are encoded by vtx genes carried by bacteriophages which facilitate their transfer between bacteria and also regulate vtx expression and toxin production. The most notable VTEC serotype is O157:H7, which was first recognised as a foodborne pathogen in 1982 following hamburger associated outbreaks involving cases of bloody diarrhoea in the USA. Since then over 400 serotypes of VTEC have been recognised, although the clinical significance of many remains unknown. In humans VTEC are responsible for a wide range of clinical manifestations. These include asymptomatic carriage, uncomplicated or mild diarrhoea, haemorrahagic colitis (bloody diarrhoea) and severe complications including haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic pupura (TTP). One feature of HUS is the damage caused to the kidneys which can result in renal failure. The predominant serotype associated with HUS and severe human disease is VTEC O157:H7, although more than 150 non-O157 serotypes have been associated with human disease. These bacteria have emerged to become the most extensively studied group of bacteria of recent times. Our knowledge of these bacteria, their physiology, underlying genetics, the regulation and structure of the phage borne vtx genes and the carriage and regulation of virulence associated genes has advanced at an impressive rate. The lack of harmonised research has resulted in similar information being generated which cannot be directly compared. Failure to standardise methods and surveillance systems has also prevented comparison of information from different studies and countries. This review provides a comprehensive account of VTEC research worldwide. It covers every aspect of VTEC research from studies with these bacteria, the characteristics of VTEC, including known virulence associated genes, methodology, clinical aspects of VTEC infection, epidemiology in humans, reservoirs for VTEC in the food chain and prevention and control of VTEC contamination. Through an international network of VTEC researchers and opinion leaders, this review has identified gaps in knowledge and aspects of VTEC research where there is currently insufficient information or a lack of understanding of these bacteria. This review gives a recent account of the published research and the major discoveries relating to VTEC.

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