Sensitivity of Escherichia coli to Atabrine Conferred by R Factor and Its Potential Clinical Significance

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Abstract
A comparative study of the inhibitory effect of Atabrine on R − and R + strains of Escherichia coli showed that R + cells were killed when grown in the presence of Atabrine, whereas R − cells were not. It would appear, therefore, that R factor confers sensitivity to Atabrine on the host cells. The “curing” of R factor from R + cells by the ultraviolet light-acridine orange method rendered the “cured” cells more resistant than even the parent R − cells. The “cured” cells reinfected by R factor were more sensitive than the “cured” cells but less sensitive than the original R + cells. After growth once in Atabrine, and even after subcultures in drug-free medium, the growth of R + cells in the presence of Atabrine was more rapid than that of the R − cells. R − cells made resistant by growing them repeatedly in streptomycin, chloramphenicol, tetracycline, and sulfathiazole in succession also showed a higher degree of sensitivity to Atabrine than the original R − cells. When mixtures of R − and R + cells were grown in 120 μg/ml of Atabrine, R + cells were killed and the culture consisted predominantly of R − cells. A mixture of R − and R + cells (1:10,000) inoculated into the Atabrine-containing medium and treated 24 hr later with chloramphenicol was completely killed.