Effect of enrofloxacin administration on excretion ofSalmonella ententidisby experimentally infected chickens and on quinolone resistance of theirEscherichia coliflora

Chickens which had been experimentally-infected with a strain of Salmonella ententidis and treated by administration of enrofloxacin at commercially recommended concentrations in the drinking water, virtually eliminated this organism from the alimentary tract. However, an initially quinolone-sensitive Escherichia coli flora present in the birds' faeces was rapidly replaced by a quinolone-resistant flora which persisted after withdrawal of the medication. Resistance to quinolone in the form of nalidixic acid was transducible from a strain of S. typhimurium to S. enterinais with bacteriophage P22.