Free Access
Vet. Res.
Volume 36, Number 3, May-June 2005
Emerging or re-emerging bacterial zoonoses
Page(s) 289 - 311
How to cite this article Vet. Res. (2005) 289-311
Vet. Res. 36 (2005) 289-311
DOI: 10.1051/vetres:2005002

Enterohaemorrhagic Escherichia coli: emerging issues on virulence and modes of transmission

Alfredo Capriolia, Stefano Morabitoa, Hubert Brugèreb and Eric Oswaldb

a  Dipartimento di Sanità Alimentare e Animale, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
b  UMR1225 INRA "Interactions Hôtes-Agents Pathogènes", École Nationale Vétérinaire de Toulouse, 23 chemin des Capelles, 31076 Toulouse Cedex, France

(Received 13 May 2004; accepted 3 August 2004)

Abstract - Enterohaemorrhagic Escherichia coli (EHEC) constitute a subset of serotypes (E. coli O157 and some other serogroups) of Shiga toxin (Stx)-producing E. coli (STEC) firmly associated with severe human illnesses like bloody diarrhoea and haemolytic uraemic syndrome. Stx production is essential but not sufficient for EHEC virulence. Most strains are capable of colonising the intestinal mucosa of the host with the "attaching and effacing" mechanism, genetically governed by a large pathogenicity island (PAI) defined as the Locus of Enterocyte Effacement. Other virulence factors carried by mobile genetic elements like PAI and plasmids have been recently described, and their role in the pathogenic process has not been fully elucidated. EHEC are zoonotic pathogens. They rarely cause disease in animals, and ruminants are recognised as their main natural reservoir. Cattle are considered to be the most important source of human infections with EHEC O157, and the ecology of the organism in cattle farming has been extensively studied. The organism has also been reported in sheep, goats, water buffalos, and deer. Pigs and poultry are not considered to be a source of EHEC and the sporadic reports may derive from accidental exposure to ruminant dejections. The epidemiology of EHEC infections has remarkably changed during the past ten years and an increasing number of unusual food vehicles have been associated with human infections. New routes of transmission have emerged, like contact with animals during farm visits and a wide variety of environment-related exposures. As for other zoonotic agents, having animals and raw products that are free from EHEC is not possible in practice. However, their occurrence can be minimised by applying high standards of hygiene in all the steps of the food production chain.

Key words: enterohemorrhagic E. coli / E. coli O157 / Shiga toxins / foodborne zoonoses

Corresponding author: Alfredo Caprioli

© INRA, EDP Sciences 2005