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Applied and Environmental Microbiology, October 2007, p. 6566-6576, Vol. 73, No. 20
0099-2240/07/$08.00+0     doi:10.1128/AEM.01086-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Impact of Feed Supplementation with Antimicrobial Agents on Growth Performance of Broiler Chickens, Clostridium perfringens and Enterococcus Counts, and Antibiotic Resistance Phenotypes and Distribution of Antimicrobial Resistance Determinants in Escherichia coli Isolates{triangledown}

Moussa S. Diarra,1* Fred G. Silversides,1 Fatoumata Diarrassouba,1 Jane Pritchard,2 Luke Masson,3 Roland Brousseau,3 Claudie Bonnet,3 Pascal Delaquis,4 Susan Bach,4 Brent J. Skura,5 and Edward Topp6

Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Agassiz, British Columbia, Canada V0M 1A0,1 British Columbia Ministry of Agriculture and Lands, Abbotsford, British Columbia, Canada V3G 2M3,2 National Research Council of Canada, Biotechnology Research Institute, Montreal, Quebec, Canada H4P 2R2,3 Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada V0H 1Z0,4 University of British Columbia, Faculty of Land and Food Systems, Vancouver, British Columbia, Canada V6T 1Z4,5 Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada N5V 4T36

Received 15 May 2007/ Accepted 14 August 2007

The effects of feed supplementation with the approved antimicrobial agents bambermycin, penicillin, salinomycin, and bacitracin or a combination of salinomycin plus bacitracin were evaluated for the incidence and distribution of antibiotic resistance in 197 commensal Escherichia coli isolates from broiler chickens over 35 days. All isolates showed some degree of multiple antibiotic resistance. Resistance to tetracycline (68.5%), amoxicillin (61.4%), ceftiofur (51.3%), spectinomycin (47.2%), and sulfonamides (42%) was most frequent. The levels of resistance to streptomycin, chloramphenicol, and gentamicin were 33.5, 35.5, and 25.3%, respectively. The overall resistance levels decreased from day 7 to day 35 (P < 0.001). Comparing treatments, the levels of resistance to ceftiofur, spectinomycin, and gentamicin (except for resistance to bacitracin treatment) were significantly higher in isolates from chickens receiving feed supplemented with salinomycin than from the other feeds (P < 0.001). Using a DNA microarray analysis capable of detecting commonly found antimicrobial resistance genes, we characterized 104 tetracycline-resistant E. coli isolates from 7- to 28-day-old chickens fed different growth promoters. Results showed a decrease in the incidence of isolates harboring tet(B), blaTEM, sulI, and aadA and class 1 integron from days 7 to 35 (P < 0.01). Of the 84 tetracycline-ceftiofur-resistant E. coli isolates, 76 (90.5%) were positive for blaCMY-2. The proportions of isolates positive for sulI, aadA, and integron class 1 were significantly higher in salinomycin-treated chickens than in the control or other treatment groups (P < 0.05). These data demonstrate that multiantibiotic-resistant E. coli isolates can be found in broiler chickens regardless of the antimicrobial growth promoters used. However, the phenotype and the distribution of resistance determinants in E. coli can be modulated by feed supplementation with some of the antimicrobial agents used in broiler chicken production.

* Corresponding author. Mailing address: P.O. Box 1000, 6947 Highway 7, Agassiz, British Columbia, Canada V0M 1A0. Phone: (604) 796-2221. Fax: (604) 796-0359. E-mail: diarram{at}agr.gc.ca

{triangledown} Published ahead of print on 7 September 2007.

Applied and Environmental Microbiology, October 2007, p. 6566-6576, Vol. 73, No. 20
0099-2240/07/$08.00+0     doi:10.1128/AEM.01086-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Bonnet, C., Diarrassouba, F., Brousseau, R., Masson, L., Topp, E., Diarra, M. S. (2009). Pathotype and Antibiotic Resistance Gene Distributions of Escherichia coli Isolates from Broiler Chickens Raised on Antimicrobial-Supplemented Diets. Appl. Environ. Microbiol. 75: 6955-6962 [Abstract] [Full Text]  
  • Lefebvre, B., Gattuso, M., Moisan, H., Malouin, F., Diarra, M. S. (2009). Genotype comparison of sorbitol-negative Escherichia coli isolates from healthy broiler chickens from different commercial farms. Poult. Sci. 88: 1474-1484 [Abstract] [Full Text]  
  • Kozak, G. K., Boerlin, P., Janecko, N., Reid-Smith, R. J., Jardine, C. (2009). Antimicrobial Resistance in Escherichia coli Isolates from Swine and Wild Small Mammals in the Proximity of Swine Farms and in Natural Environments in Ontario, Canada. Appl. Environ. Microbiol. 75: 559-566 [Abstract] [Full Text]  


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