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Verotoxin producing Escherichia coli (VTEC) have been associated with disease outbreaks of diarrhea hemorrhagic colitis and hemolytic-uremic syndrome in humans. Contamination occurs mainly by ingestion of beef and dairy products, but water and person to person transmission have also been described. Most of the clinical signs are due to the production of Stx1 and/or Stx2 Shiga toxins, also called verotoxins. Other virulence factors include enterohemolysin, and the product of the eae gene, intimin, involved in the attaching and effacing adherence phenotype. The predominant serotype is O157:H7, but VTEC strains of more than one hundred serotypes can cause human disease. In order to determine the prevalence of VTEC infections among children in the central part of France, stool samples from hospitalized children were examined for stx1 and stx2 genes by using a polymerase chain reaction (PCR) technique. From October 1997 to September 1998, 658 stool samples were analysed: among them 19 (3%) were stx-PCR positive. Only 8 children out of 19 had diarrhea, and for 5 of them, an enteric pathogen other than VTEC was isolated. VTEC strains were isolated from 10 samples: most of the isolates did not produce verotoxins at a high level, and they did not belong to serotypes associated with pathogenicity, which might explain the absence of relationship between VTEC isolation and pathogenicity in our study.

Escherichia coli O157:H7 is now recognised as an important human pathogen. Illness caused by E. coli O157:H7 infection can range from self limited, watery diarrhea to life-threatening manifestations such as hemorrhagic colitis, hemolytic uremic syndrome or thrombotic thrombocytopenic purpura. The mode of transmission is primarily through food (e.g. undercooked minced beef products, especially beef burgers, raw cows' milk and cheese, contaminated pasteurised milk and untreated water.). Studies to date indicate that cattle is an important reservoir of the organism. Public health measures to control VTEC infection are broadly similar to the measures needed to control other gastro-intestinal infections. Because of the potential low infection dose, laboratory diagnosis of O157 VTEC in food samples has developed over recent years with the use of liquid enrichment and the development of methods such as immunomagnetic separation. VTEC of other serogroups than O157 have no reliable biochemical, serological or morphological characteristics (other than VT production itself) to distinguish them from commensal E. coli. Thus to detect VTEC other than O157 and phenotypic variants of E. coli O157 in food, we have to use methods for detection of verocytotoxin production and VT genes.