ARS | Publication request: EFFECT OF THE ANTI-MICROBIAL FEED ADDITIVES MONENSIN, LAIDLOMYCIN PROPIONATE, AND BAMBERMYCIN ON FECAL SHEDDING AND ANTI-MICROBIAL SUSCEPTIBILITY OF E. COLI 0157:H7 AND SALMONELLA TYPHIMURIUM

Submitted to: Abstracts World Buiatrics Congress
Publication Type: Abstract Only
Publication Acceptance Date: August 21, 2001
Publication Date: N/A

Technical Abstract: Escherichia coli 0157:H7 and Salmonella are widely recognized as important agents of food-borne disease. The use of ionophores in feeding ruminants is widespread in the United States and has attracted recent interest due to the apparent temporal relationship between ionophore use and the increase in E. coli 0157:H7 cases. Two experiments were conducted to evaluate the effects of short-term feeding of ionophores on fecal shedding, intestinal concentrations, and antimicrobial susceptibility of E. coli 0157:H7 and Salmonella Typhimurium in growing lambs. Sixteen lambs were used in each experiment, four lambs per treatment group: monensin (MON), laidlomycin propionate (LP), bambermycin (BBM) and a control treatment). Lambs were fed their respective ionophore for 24 days. After 12 days on ionophores, lambs were experimentally infected with a non-toxigenic strain of E. coli 0157:H7 or Salmonella Typhimurium and fecal shedding was monitored daily. On day 24, lambs were humanely euthanized and tissues and contents sampled from the rumen, ileum, cecum, and rectum. No differences (P > 0.05) in fecal shedding of Salmonella or E. coli were found, although E. coli concentration appeared to decrease more quickly in control animals compared with ionophore treated animals. Gut contents and tissue samples for Salmonella or E. coli incidence were not different (P > 0.05) among treatments. These initial studies found minimal effects of short-term ionophore feeding on E. coli and Salmonella shedding or on anti-microbial susceptibility, but indicate that detailed, longer term studies are needed.