Sensitivity of Escherichia coli O157:H7 strain 932 to selected anticoccidial drugs in broiler chicks.

ABSTRACT

The ability of selected anticoccidial drugs to inhibit the colonization of day-old male broiler chicks (Cornish Rocks) by Escherichia coli O157H7, strain 932 was examined. Chicks were challenged with 1.8 x 10(9) E. coli O157H7 on Day 1, and fed diets supplemented with three selected anticoccidial drugs; monensin, nicarbazin, or robenidine. The cecal and colon fecal contents of the chicks were removed on Day 7, 14, and 21 postinoculation and examined for the concentration of E. coli O157 H7 per gram of contents. Monensin effectively reduced cecal and colon colonization of the chicks by E. coli O157H7. By Day 7, there were significant reductions in the bacterial population of the cecal contents of chicks receiving the monensin-medicated feed, and by Day 21 no E. coli O157H7 was recovered from the cecal and colon contents. The bacterial counts in the colon contents of the nicarbazin- and robenidine-medicated and unmedicated chicks were significantly higher than the monensin-treated chicks. Bacterial populations in the colon contents were high only when there were high bacterial concentrations in the cecal contents.