Enterohaemorrhagic Escherichia coli O157 : H7 infections of man have been associated with consumption of unpasteurized goat's milk and direct contact with kid goats on petting farms, yet little is known about colonization of goats with this organism. To assess the contribution of flagella and intimin of E. coli O157 : H7 in colonization of the goat, 8-week-old conventionally reared goats were inoculated orally in separate experiments with 1310 10 c.f.u. of a non-verotoxigenic strain of E. coli O157 : H7 (strain NCTC 12900 Nal r ), an aflagellate derivative (DMB1) and an intimin-deficient derivative (DMB2). At 24 h after inoculation, the three E. coli O157 : H7 strains were shed at approximately 5310 4 c.f.u. (g faeces) À1 from all animals. Significantly fewer intimin-deficient bacteria were shed only on days 2 (P ¼ 0 . 003) and 4 (P ¼ 0 . 014), whereas from day 7 to 29 there were no differences. Tissues from three animals inoculated with wild-type E. coli O157 : H7 strain NCTC 12900 Nal r were sampled at 24, 48 and 96 h after inoculation and the organism was cultured from the large intestine of all three animals and from the duodenum and ileum of the animal examined at 96 h. Tissues were examined histologically but attaching-effacing (AE) lesions were not observed at any intestinal site of the animals examined at 24 or 48 h. However, the animal examined at 96 h, which had uniquely shed approximately 1310 7 E. coli O157 : H7 (g faeces) À1 for the preceding 3 days, showed a heavy, diffuse infection with cryptosporidia and abundant, multifocal AE lesions in the distal colon, rectum and at the recto-anal junction. These AE lesions were confirmed by immunohistochemistry to be associated with E. coli O157 : H7.
INTRODUCTIONEscherichia coli serotype O157 : H7 infection was first recognized in the early 1980s to be associated with haemorrhagic colitis, haemolytic-uraemic syndrome and thrombocytopaenic purpura in man (Karmali et al., 1983;Riley et al., 1983). Human infection and the sequelae of infection have been well documented subsequently (Smith & Scotland, 1993;Boyce et al., 1995;Swinbanks, 1996) and E. coli O157 : H7, classified as belonging to the recently defined enterohaemorrhagic E. coli pathotype, is regarded worldwide as the leading cause of both haemorrhagic colitis and haemolytic-uraemic syndrome.Transmission of E. coli O157 : H7 is faecal-oral (Pepin et al., 1997;Locking et al., 2001), with cattle considered as the primary reservoir (Griffin & Tauxe, 1991) and sheep also recognized as a significant reservoir (Chapman et al., 1997;Heuvelink et al., 1998;Meng et al., 1998;Fegan & Desmarchelier, 1999). Other potential sources of these organisms have been described, including rabbits and seagulls amongst other species (Griffin & Tauxe, 1991;Pritchard et al., 2001).Several recent reports cite goats as potential sources of E. coli O157 : H7 infection. Shukla et al. (1995) reported four human cases of bloody diarrhoea affecting one adult and three children aged 2-4 years, which were traced to a farm visitor cent...
