Submitted to: National Foundation for Infectious Disease
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2003
Publication Date: June 23, 2003
Citation: Bischoff, K.M., Edrington, T.S., Callaway, T.R., Genovese, K.J., Beier, R.C., Nisbet, D.J. 2003. Antimicrobial resistance in Salmonella isolated from dairy calves in Texas [abstract]. National Foundation for Infectious Disease. p. 44. Technical Abstract: The intestinal tracts of food animals represent a major reservoir for Salmonella, one of the most common agents of human food-borne illness. Since dairy cattle are often used for beef production, this study was performed to characterize the diversity of serotypes and the antimicrobial susceptibility phenotypes of Salmonella isolated from dairy calves. Fifty fecal samples were collected from a dairy-calf farm in Texas that was experiencing severe losses due to scours. Thirty-five samples (70%) tested positive for Salmonella. The most prevalent Salmonella serotype was Kinshasha (23/35), followed by Agona (4/35), Infantis (2/35), Newport (2/35), Montevideo (2/35), Lille (1/35), and Newington (1/35). One-hundred-five isolates were characterized for susceptibility to 26 antimicrobial agents of human and veterinary therapeutic significance. High rates of resistance to the following drugs that are commonly used for treatment of colibacillosis in livestock were observed: ampicillin (88%), apramycin (83%), neomycin (86%), spectinomycin (91%), chlortetracycline (91%), and oxytetracycline (90%). Multiple drug resistance was frequently observed, with 86% of the Salmonella isolates resistant to 22 or more antimicrobials. In bacterial conjugation experiments, ampicillin resistance was transferred from Salmonella Kinshasa to an Escherichia coli recipient. Chloramphenicol, streptomycin, sulphamethoxazole, tetracycline, cephalothin, and cefoxitin resistance all co-transferred with ampicillin resistance. An experimental antimicrobial, sodium chlorate, was found to inhibit the growth of the Salmonella isolates. The prevalence of multi-drug resistant Salmonella in dairy calves emphasizes the need for alternative pathogen control strategies to help the producer maintain animal health and consequently, produce a safer food product.