Verotoxin-producing Escherichia coli (VTEC), enteropathogenic E. coli (EPEC) and necrotoxigenic E. coli (NTEC) isolated from healthy cattle in Spain J.A. Orden, D. Cid, J.A. Ruiz-Santa-Quiteria, S. Garcı ´a, S. Martı ´nez and R. de la Fuente Departamento de Patologı´a Animal I, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain 2001/326: received 19 October 2001, revised 28 January 2002 and accepted 27 February 2002 J.A. ORDEN, D. CID, J.A. RUIZ-SANTA-QUITERIA, S. GARCI ´ A, S. MARTI ´ NEZ AND R. DE LA FUENTE. 2002. Aims: To determine the prevalence and characteristics of verotoxigenic Escherichia coli (VTEC), enteropathogenic E. coli (EPEC) and necrotoxigenic E. coli (NTEC) in healthy cattle. Methods and Results: Faecal samples from 412 healthy cattle were screened for the presence of VTEC, EPEC and NTEC. Four isolates from each sample were studied. VTEC, EPEC and NTEC were isolated in 8Æ7%, 8Æ2% and 9Æ9% of the animals, respectively. VTEC and NTEC were isolated more frequently from calves and heifers than from adults. Seventy (4Æ2%), 69 (4Æ2%) and 74 (4Æ5%) of the 1648 E. coli isolates were VTEC, EPEC and NTEC, respectively. Seventeen (24Æ3%) of the VTEC strains were eae-positive. Thirty-six (51Æ4%) of VTEC strains belonged to E. coli serogroups associated with haemorrhagic colitis and haemolytic uraemic syndrome in humans. The serogroups most prevalent among the EPEC strains were O10, O26, O71, O145 and O156. Conclusions: Healthy cattle are a reservoir of VTEC, EPEC and NTEC. Significance and Impact of the Study: Although most of the VTEC strains were eae-negative, a high percentage of VTEC strains belonged to serogroups associated with severe disease in humans. INTRODUCTION Verotoxin-producing Escherichia coli (VTEC) strains may produce two types of verotoxins (VT1 and VT2). VT1 is functionally and structurally related to Shiga toxin synthes- ized by Shigella dysenteriae type 1. VT1 and VT2 are also termed Shiga-like toxins (SLT-I and SLT-II) (Levine 1987; Karmali 1989; Griffin and Tauxe 1991). VTEC may cause severe disease in humans, such as haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS) (Karmali 1989; Griffin and Tauxe 1991). Those VTEC strains which are able to induce HC and HUS are called enterohaemorrhagic E. coli (EHEC) (Levine 1987). Consumption of beef or raw milk has been suspected or confirmed as the most likely source of infection in diverse outbreaks which have occurred mainly in Canada, the USA and the UK during the last decade (Blanco et al. 1996a). The predominant EHEC serotype associated with human infection and death is O157:H7 (Levine 1987; Karmali 1989; Griffin and Tauxe 1991). In addition, outbreaks of disease have been traced to non-O157 VTEC serotypes, especially in Europe, Australia and Asia (Kudva et al. 1997). It is not known whether all variants of VTEC are equally pathogenic for humans, and it is possible that VT produc- tion alone may not be sufficient for VTEC to cause disease (Beutin et al. 1995). A factor that may affect virulence of VTEC is the ability to cause the attaching and effacing (AE) lesion in the intestinal mucosa (Jerse et al. 1990; Beutin et al. 1995). In cattle, the role in disease of VTEC is controversial, but strains that produce VT1 only and possess the eae gene have been associated with diarrhoea in calves (Orden et al. 1998). Some non-VTEC strains have the ability to cause the AE lesion in the small intestine of humans and are denominated Correspondence to: Dr R. de la Fuente, Departamento de Patologı´a Animal I, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain (e-mail: rifuente@vet.ucm.es). ª 2002 The Society for Applied Microbiology Journal of Applied Microbiology 2002, 93, 29–35