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Genotype, Serotype, and Antibiotic Resistance of Sorbitol-Negative Escherichia coli Isolates from Feedlot Cattle

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Rectal fecal samples from 80 steers receiving Rumensin, Revalor-S, and Liquamycin alone or in combination for growth promotion and disease prevention were examined for the presence of non-O157:H7 Shiga toxin–producing Escherichia coli. All isolates were identified with the API 20E test, virulence genes were detected with a PCR assay, and antibiotic susceptibilities were determined with the Sensititre system. Of the 153 E. coli isolates recovered 126 (82.3%) were sorbitol negative. Isolates were classified into 14 biochemical E. coli groups; 51.6% were negative for arginine dihydrolase, ornithine decarboxylase, sorbitol, and saccharose reactions but positive for lysine decarboxylase, indole production, and rhamnose reactions. Twenty-one O:H serotypes were detected in the 153 E. coli isolates. The most frequent serotypes were O2:H42 (49.7% of isolates), O49:NM (13.7%), O?:H25 (9.2%), and O10:NM (7.2%). One isolate of E. coli O172:H25 and one of E. coli O157: H39 were found. The stx 1 gene was found in the two E. coli O98:H25 isolates. The eaeA and e-hlyA genes were detected in 21, 14, and 10 isolates of serotypes O49:NM, O?:H25, and O10:NM, respectively, and in each isolate of serotype O156:H25 and O172:H25. Four E. coli O132:H18 isolates were multiresistant to ampicillin, chloramphenicol, kanamycin, streptomycin, and sulfisoxazole. Tetracycline resistance due to the tet(B) gene was observed in 74 of the 76 E. coli O2:H42 isolates. Except for one isolate, all tetracycline-resistant isolates were negative for the virulence genes eaeA and e-hlyA or stx 1. Pulsed-field gel electrophoresis typing revealed that the tetracycline-resistant serotypes were genetically diverse. Our data illustrate that cattle are a potential source of some atypical antibiotic-resistant E. coli isolates that harbor virulence genes.

Document Type: Research Article

Affiliations: 1: Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, P.O. Box 1000, 6947 Highway 7, Agassiz, British Columbia, Canada V0M 1A0 2: Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, P.O. Box 90, 2000 College Street, STN Lennoxville, Quebec, Canada J1M 1Z3 3: Centre de Valorisation de la Diversité Microbienne, Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1K 2R1 4: Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, P.O. Box 5000, 4200 Highway 97, Summerland, British Columbia, Canada V0H 1Z0 5: Lacombe Research Centre, Agriculture and Agri-Food Canada, 6000 C & E Trail, Lacombe, Alberta, Canada T4L 1W1 6: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, 110 Stone Road West, Guelph, Ontario, Canada N1G 3W4

Publication date: 2009-01-01

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