Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2003
Publication Date: 3/29/2004
Citation: BISCHOFF, K.M., EDRINGTON, T.S., CALLAWAY, T.R., GENOVESE, K.J., NISBET, D.J. CHARACTERIZATION OF ANTIMICROBIAL RESISTANT SALMONELLA KINSHASA FROM DAIRY CALVES IN TEXAS. LETTERS IN APPLIED MICROBIOLOGY. 2004. V. 38. P. 140-145. Interpretive Summary: Dairy calves are susceptible to infection with Salmonella, disease-causing bacteria that cause severe diarrhea and can kill infected animals. Fifty samples from animals on a dairy calf farm in the southwestern United States were analyzed for Salmonella. Thirty-five of the samples (70%) contained Salmonella. Sixty-six percent of the Salmonella isolates were identified as a rare type called Salmonella Kinshasa. Most of the Salmonella isolates were resistant to antibiotic drugs that are usually used to treat diarrhea in dairy calves. Growth of the Salmonella isolates was inhibited by a chemical called sodium chlorate. This study emphasizes the possibility of using alternative strategies to antibiotics for treating infected animals.
Technical Abstract: Fifty fecal samples were collected from a dairy-calf farm in the southwestern United States that was experiencing high mortality rates due to severe diarrhea, and were characterized for the presence of antimicrobial resistant Salmonella. Thirty-five samples (70%) tested positive for Salmonella. The most prevalent serotype was Salmonella Kinshasa (23/35), followed by S. Agona (4/35), S. Infantis (2/35), S. Newport (2/35), S. Montevideo (2/35), S. Lille (1/35), and S. Newington (1/35). One hundred five isolates were characterized for susceptibility to 26 antimicrobial agents of human and veterinary therapeutic significance. The Salmonella isolates exhibited high rates of resistance to the following drugs that are commonly used for treatment of colibacillosis in livestock: 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, but ceftriaxone and ceftiofur resistance did not. An experimental antimicrobial, sodium chlorate, was found to inhibit the growth of the Salmonella isolates in vitro. The high prevalence of multi-drug resistant Salmonella in dairy calves emphasizes the need for alternative intervention strategies, such as administration of chlorate, for effective control of enteric disease in livestock.