Oral and Rectal Administration of Bacteriophages for Control of Escherichia coli O157:H7 in Feedlot Cattle
Abstract:This study compared oral and rectal administration of O157-specific bacteriophages for mitigating the fecal shedding of Escherichia coli O157 by experimentally inoculated steers. Fecal shedding of nalidixic acid–resistant (NalR) E. coli O157:H7 was monitored over 83 days after oral (ORL; 3.3 × 1011 PFU), rectal (REC; 1.5 × 1011 PFU), both oral and rectal (O+R; 4.8 × 1011 PFU), or no (CON; control) treatment with a four-strain O157-specific bacteriophage cocktail in multiple doses. Bacteriophages were enumerated by plaque assay, and NalR E. coli O157:H7 by direct plating on sorbitol MacConkey agar supplemented with cefixime, potassium tellurite, and nalidixic acid. Orally treated steers produced the fewest NalR E. coli O157:H7 culture-positive samples (P < 0.06) compared with REC and O+R steers, but this number was only nominally lower (P = 0.26) than that for the CON steers. The overall mean shedding level (log CFU per gram of feces) was higher for REC steers (P < 0.10) than for steers of the other treatment groups. Despite the shedding of higher mean bacteriophage levels (log PFU per gram of feces) by ORL and O+R than by CON and REC steers, there was no difference (P > 0.05) in the number of E. coli O157–positive samples among treatments. Bacteriophage was isolated from CON steers, indicating that these steers acquired the bacteriophage from the environment and shed the phage at a level similar to that of REC steers (P = 0.39). Continuous bacteriophage therapy may be an efficacious method for mitigating shedding of E. coli O157:H7 in cattle, providing that the host bacterium does not develop resistance. This therapy may be especially advantageous if nontreated cattle can acquire this biocontrol agent from the feedlot environment.
Document Type: Research Article
Affiliations: 1: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5; Alberta Agriculture and Rural Development, Agriculture Centre, Lethbridge, Alberta, Canada T1J 4V6; Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada T1J 4B1 2: Alberta Agriculture and Rural Development, Agriculture Centre, Lethbridge, Alberta, Canada T1J 4V6 3: Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland, British Columbia, Canada V0H 1Z0 4: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5 5: Public Health Agency of Canada, Laboratory for Foodborne Zoonoses, Guelph, Ontario, Canada N1G 3W4 6: Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada T1J 4B1
Publication date: February 1, 2009
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