Bacteriostatic actions of some tetracyclines

Abstract

Abstract 6-Demethyl-6-deoxytetracycline, 6-methyleneoxytetracycline, 7-chlortetracycline and 7-chlor-6-demethyltetracycline inhibit Aerobacter aerogenes in glucose-mineral salt media, by two modes of action, I and II, shown by tetracycline and oxytetracycline (Jones & Morrison, 1962; 1963): Mode II by 6-demethyl-6-deoxytetracycline is not detected by inhibition of growth of the organism but by inhibition of the anaerobic consumption of pyruvate which is also a consequence of Mode II. The chlorine-containing tetracyclines also inhibit the growth of the organism by a third mode of action (III) which is probably an interference with the provision of d-glutamate during aerobic growth. The inhibitions produced by a tetracycline are linearly related to the amount of the antibiotic in the molecular form present in the cultures. All three modes of action so far described are probably interferences with hydrogen transfer reactions. The bacteriostatic activities of six tetracyclines are compared.