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Title: ANTIMICROBIAL SUSCEPTIBILITY PATTERNS OF SALMONELLA SPP ISOLATES FROM CATTLE IN FEEDLOTS

Author
item DARGATZ, D - USDA-APHIS
item Cray, Paula
item Ladely, Scott
item FERRIS, K - USDA-APHIS
item GREEN, A - USDA-APHIS
item HEADRICK, MARCIA - FDA-CVM

Submitted to: Journal of the American Veterinary Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2002
Publication Date: 7/15/2002
Citation: Dargatz, D.A., Cray, P.J., Ladely, S.R., Ferris, K.E., Green, A.I. 2002. Antimicrobial susceptibility patterns of salmonella spp isolates from cattle in feedlots. Journal of the American Veterinary Medical Association. Vo. 221. No. 2. P. 268-272.

Interpretive Summary: Antimicrobial resistance has become a global concern and impacts both veterinary medicine and public health through the potential for therapeutic failures. Antimicrobial resistance among bacterial isolates from animals is also of concern due to the potential for these organisms to be food borne. The objective of this study was to evaluate the susceptibility patterns of Salmonella isolates from cattle in feedlots throughout the U.S. Fecal samples were collected from the floor of 2 pens in each of 100 feedlots. 280 Salmonella isolates were recovered after bacteriologic culture from 38 pens from 37 feedlots in 13 states. Of these, 263 isolates were available for antimicrobial susceptibility testing. Less than five percent of the isolates were resistant to any single antimicrobial tested with the exception of tetracycline (23.2% resistant) and sulfamethoxazole (5.7% resistant). Most (74.9%) of the isolates were sensitive to all antimicrobials tested. Antimicrobial resistance was not related to the presence or absence of antimicrobials in the current ration being fed at the time of sample collection. This information is important for the industry and veterinarians as they are required to treat animals that may be ill. It is important for the regulatory agencies as they design new drug use guidelines. The determination of current susceptibility patterns will be critical for the identification of trends in antimicrobial resistance among Salmonella isolates in the future.

Technical Abstract: We conducted a cross-sectional study to evaluate the antimicrobial suseptibility patterns of Salmonella isolates from feedlot cattle. Fecal samples were collected from the floor of 2 pens in each of 100 feedlots. 280 Salmonella isolates were recovered after bacteriologic culture from 38 pens from 37 feedlots in 13 states. Of these, 263 isolates were available for antimicrobial susceptibility testing to 16 antimicrobials using micro-broth dilution breakpoint plates. Less than five percent of the isolates were resistant to any single antimicrobial tested with the exception of tetracycline (23.2% resistant, n=61) and sulfamethoxazole (5.7% resistant, n=15). Most (74.9%, n=197) of the isolates were sensitive to all antimicrobials tested. The proportion of isolates resistant to any antimicrobials varied by serotype. None of the Salmonella Typhimurium (including var. Copenhagen) isolates resistant to ampicillin, chloramphenicol, sulfamethoxazole, streptomycin, and tetracycline were Salmonella Typhimurium DT 104. Antimicrobial resistance was not related to the presence or absence of antimicrobials in the current ration being fed at the time of sample collection.