The Effect of Tetracycline upon Establishment of <i>Escherichia coli</i> of Bovine Origin in the Enteric Tract of Man

Abstract

S ummary . Human volunteers were given orally 0, 50 or 1000 mg of tetracycline/day for the 4 days preceding and the 5 days following ingestion of 1–2 x 10 6 cells of tetracycline resistant Escherichia coli strain x‐314 of bovine origin. Of those receiving 0, 50 or 1000 mg of tetracycline/day, 9/13, 5/9 and 12/13, respectively, excreted the organism at least once during the 25‐day sampling period. Significant differences were not observed between subjects receiving 0 or 50 mg of tetracycline/day with respect to the length of time the coliform was recovered from faeces, or the maximum proportion of the total coliforms found to be E. coli x‐314. Those receiving 1000 mg of tetracycline/day shed E. coli x‐314 for longer periods and the latter's contribution to the coliform population was greater than in those subjects receiving 0 or 50 mg of tetracycline/day. It was concluded that 1000, but not 50 mg, of tetracycline/day taken orally potentiates the establishment of a tetracycline resistant E. coli in the enteric tract of man.