Changes in Tetracycline Susceptibility of Enteric Bacteria following Switching to Nonmedicated Milk Replacer for Dairy Calves
A randomized intervention study was conducted to determine if discontinuing use of calf milk replacer medicated with oxytetracycline results in increased tetracycline susceptibility in Salmonella and Campylobacter spp. and Escherichia coli in dairy calves over a 12-month period. Dairy herds with ent...
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Published in | Journal of Clinical Microbiology Vol. 46; no. 6; pp. 1968 - 1977 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
American Society for Microbiology
01.06.2008
American Society for Microbiology (ASM) |
Subjects | |
Online Access | Get full text |
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Summary: | A randomized intervention study was conducted to determine if discontinuing use of calf milk replacer medicated with oxytetracycline results in increased tetracycline susceptibility in Salmonella and Campylobacter spp. and Escherichia coli in dairy calves over a 12-month period. Dairy herds with enteric bacteria with known low tetracycline susceptibility were enrolled for the study. Fecal samples from preweaned calves and environmental samples were collected from eight dairy herds in Michigan and New York State. Samples were collected monthly for 3 months prior to and 12 months after four of the eight herds discontinued medicated milk replacer feeding. Salmonella and Campylobacter spp. and E. coli were isolated, and antimicrobial susceptibility testing was conducted using automated broth microdilution. A total of 804 intervention and 1,026 control calf fecal samples and 122 intervention and 136 control environmental samples were collected for testing. No differences in owner-reported morbidity and mortality between treatment groups were seen. The intervention was significantly associated with increasing tetracycline susceptibility in E. coli and SALMONELLA: Tetracycline susceptibility increased in intervention herds for the first 3 months after switching to nonmedicated milk replacer but declined in subsequent months. Discontinuing the practice of feeding medicated milk replacers to calves increased tetracycline susceptibility in E. coli and Salmonella on dairy farms, without increasing cattle disease, but declines in effectiveness after 3 months suggest that other factors contribute to decreasing susceptibility on the farm. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Corresponding author. Mailing address: A-109 Veterinary Medical Center, Michigan State University, East Lansing, MI 48824-1314. Phone: (517) 353-5941. Fax: (517) 432-0976. E-mail: kaneene@cvm.msu.edu |
ISSN: | 0095-1137 1098-660X 1098-5530 |
DOI: | 10.1128/JCM.00169-08 |