Effects of low concentrations of ampicillin in feed on the intestinal Escherichia coli of chicks |
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Authors: | Selwa Al-Sam A.H. Linton P.M. Bennett M. Hinton |
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Affiliation: | Department of Microbiology, University of Bristol, School of Medical Sciences, Bristol;Department of Veterinary Medicine, University of Bristol, Langford, Avon, UK |
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Abstract: | Ampicillin in low concentrations (1.7 and 5 g t-1) was incorporated in the feed given to 1-d-old chicks for 2 weeks. This was sufficient to select, in the intestinal contents, resistant Escherichia coli strains for which the minimum inhibitory concentration of ampicillin was > 100 μg ml-1. Different clones of E. coli were identified by their biotype, pattern of resistance to antibacterial agents and plasmid profile (designated P-P types). The experiment was repeated twice and the average proportion of ampicillin-resistant P-P types among 72 isolates of E. coli from chicks given feed containing 0, 1.7 and 5 g ampicillin t-1 were 10%, 31% and 46% respectively. |
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