Effect of bambermycins on Escherichia coli and antibiotic resistance in calves

Dealy, J.; Moeller, M.W.

Journal of Animal Science 45(6): 1239-1242


ISSN/ISBN: 0021-8812
PMID: 342477
DOI: 10.2527/jas1977.4561239x
Accession: 005222357

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Fourteen 8-wk-old calves, infected with Salmonella typhimurium, were used to study the effect of bambermycins in feed on the quantity and antibiotic susceptibility of fecal E. coli. Calves were divided into 2 treatment groups. The control group consisting of 7 animals received nonmedicated feed and had no exposure to antibiotics during the trial. The test group of 7 calves was fed 10 mg/head per day bambermycins in feed for 61 days. Special precautions were taken to eliminate cross-contamination between animals in both treatment groups. Homogenized fecal samples were monitored to enumerate E. coli before and after medication. Five colonies of E. coli from each fecal specimen were isolated and tested for susceptibility to 10 antibiotics. Bambermycins supplemented feed did not significantly increase the number of intestinal E. coli in calves. Bambermycins fed calves showed a significant decrease in the percent of E. coli resistant to streptomycin and oxytetracycline but an increase in the percent resistant to bambermycins. Feeding bambermycins diets significantly reduced the percent of E. coli multiply resistant to 2 and 3 antibiotics.