The persistence of R-plasmid-carrying E. coli in a married couple, one of whom was receiving antibiotics.

The aerobic Gram-negative intestinal flora of two individuals, husband and wife, has been followed for about 20 months. The wife was receiving prolonged tetracycline treatment for acne during the first year of the study and was found to carry a large proportion of tetracycline resistant E. coli in her faecal flora even after the tetracycline treatment had ended. A brief therapeutic course of ampicillin during the period when no tetracycline was being taken resulted in the temporary disappearance of the tetracycline resistant flora, but this returned, even though no tetracycline was being taken, as soon as the ampicillin ended. The husband took no antibiotics during the period under study but was frequently found to excrete the same resistant E. coli as his wife. Moreover, the plasmids carried by the tetracycline resistant strains in the wife and the husband were often indistinguishable. This suggests that R-plasmids may spread from people under treatment to close relatives who have not been treated.