Effect of Oral Tetracycline on the Occurrence of Tetracycline-Resistant Strains of Escherichia coli in the Intestinal Tract of Humans

Abstract
Serial samples of feces from normal human subjects were analyzed for tetracycline-resistant strains of Escherichia coli. Subjects were found to be excreting tetracycline-resistant strains in amounts fluctuating with time. Ingestion of tetracycline increased both the number of individuals excreting tetracycline-resistant strains of E. coli and the proportion of the total E. coli isolates resistant to the antibiotic.