Colonization of 8-week-old conventionally reared goats by Escherichia coli O157 : H7 after oral inoculation

Abstract

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...

Role of Intimin-Tir Interactions and the Tir-Cytoskeleton Coupling Protein in the Colonization of Calves and Lambs by Escherichia coli O157:H7

“…The 85-170 Nal r ⌬tir and 85-170 Nal r ⌬eae ⌬tir mutant strains were constructed by Stevens et al (46) and Vlisidou et al (49), respectively. Studies of lambs were performed with the stx-negative strain NCTC12900 Nal r , an isogenic NCTC12900 Nal r eae::Cam r mutant (31), and with NCTC12900 Nal r tir::Str r . The tir mutant of NCTC12900 Nal r was made by the insertion of a nonpolar streptomycin resistance cassette into tir followed by allelic exchange using a positive-selection suicide vector.…”

Colonization, Persistence, and Tissue Tropism ofEscherichia coliO26 in Conventionally Reared Weaned Lambs

“…The numbers of organisms of each of the four E. coli O26 strains tested and control strain NCTC12900 recovered from each tissue sample were similar (Table 3), the differences were not significant (P ϭ 0.259), and AE lesions were observed in IHC-stained sections of loops that were inoculated with two of the O26 strains (Table 3). No AE lesions were detected in loops inoculated with the control strain NCTC12900, although lesions have been previously observed in this model with this strain (60) and after oral inoculation in the cecum, colon, rectum, and RAJ of 5-week-old lambs (34); in the distal colon, rectum, and RAJ of 8-week-old goats (32); and in the ileum of 6-day-old goats (62).…”

“…Although sheep were demonstrated to be free from E. coli O157 and O26, it is possible that previous exposure to another AEEC strain may have induced cross-protective immunity. The induction of AE lesions by NCTC12900 has been observed on the intestinal mucosa of 6-week-old lambs and the gastrointestines of 6-day-and 8-week-old goats after oral inoculation (32,62).…”

“…Other than strain EC335/98, which is naturally resistant (Ͼ250 g/ml) to streptomycin (Str r ) only, all strains were fully sensitive to the antibiotics (n ϭ 16) tested (VLA reference laboratory procedure). The E. coli O157:H7 NCTC12900 Nal r strain lacks the stx 1 and stx 2 toxin genes, possesses the ␥-intimin gene, and has been fully characterized previously (16,32).…”

“…Light and electron microscopy and immunohistochemistry were performed essentially as described previously (32,33,63). Briefly, tissues were fixed in 10% neutral buffered Formalin, processed to wax, and sectioned at 4 m. Sections were rehydrated prior to assembly into a Shandon Sequenza staining apparatus.…”