Effect of Bambermycins on Escherichia Coli and Antibiotic Resistance in Calves

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Abstract
Fourteen 8-week-old calves, infected with Salmonella typhimurium, were used to study the effect of bambermycins2 in feed on the quantity and antibiotic susceptibility of fecal Escherichia coli. Calves were divided into two treatment groups. The control group consisting of seven animals received nonmedicated feed and had no exposure to antibiotics during the trial. The test group of seven calves was fed 10 mg/head/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 oxytetra-cycline but an increase in the percent resistant to bambermycins. Furthermore, feeding bambermycins diets significantly reduced the percent of E. coli multiply resistant to two and three antibiotics. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.

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