Effects of low concentrations of ampicillin in feed on the intestinal Escherichia coli of chicks.
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 micrograms 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.
al-Sam
S
S
Department of Microbiology, University of Bristol, School of Medical Sciences UK.
Linton
A H
AH
Bennett
P M
PM
Hinton
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M
D000667:Ampicillin / Q000032:analysis / Q000494:pharmacology*; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002645:Chickens; D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects*; D007422:Intestines / Q000382:microbiology*
D000667:Ampicillin