Prevalence of antimicrobial resistance among Salmonella on midwest and northeast USA dairy farms

K. A. Ray, L. D. Warnick, R. M. Mitchell, J. B. Kaneene, P. L. Ruegg, S. J. Wells, C. P. Fossler, L. W. Halbert, K. May

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35 Scopus citations


The objective of this study was to determine the prevalence of antimicrobial resistance among Salmonella isolated from dairy herds in New York, Minnesota, Michigan, and Wisconsin, USA. Serogroup and antimicrobial susceptibility characteristics were determined for Salmonella from cattle and environmental samples collected during August 2000-October 2001 as part of a longitudinal study where 129 herds were visited at 2-month intervals. Salmonella isolates were tested (using a broth microdilution method) for susceptibility to amoxicillin/clavulanic acid, ampicillin, ceftiofur, ceftriaxone, cephalothin, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, nalidixic acid, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim/sulfamethoxazole. Of the 1506 isolates tested for minimum inhibitory concentrations to these 14 antimicrobial agents, 81.2% were pan-susceptible and for most herds (81.6%) the predominant antimicrobial resistance pattern was pan-susceptible. At least 1 Salmonella isolate resistant to 5 or more antimicrobial agents was found on 23.6% of herds. This resistance phenotype was most common among serogroups B and E1 and among samples from calves and farmer-designated sick cows. Resistant samples most frequently exhibited resistance to tetracycline, streptomycin, and/or ampicillin. No samples were resistant to ceftriaxone (though 13 were in the intermediate range), and very few samples were resistant to ciprofloxacin (n = 1), nalidixic acid (n = 5), or trimethoprim/sulfamethoxazole (n = 7).

Original languageEnglish (US)
Pages (from-to)204-223
Number of pages20
JournalPreventive Veterinary Medicine
Issue number2-4
StatePublished - May 16 2007

Bibliographical note

Funding Information:
This work was supported by National Research Initiative Competitive (Epidemiological Approaches to Food Safety) Grant 99-35212-8563 and NYC-478862 from the USDA Cooperative State Research, Education, and Extension Service. We thank the participating dairy farmers in the four states for their work on this study, and Amy Campbell and RoseAnn Miller for their technical support.

Copyright 2008 Elsevier B.V., All rights reserved.


  • Antimicrobial resistance
  • Dairy cattle
  • Salmonella
  • Serogroup


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