Effect of azasteroids on gram-positive bacteria.

A group of nitrogen-containing steroids closely related in structure was screened for antibacterial activity, by use of Bacillus subtilis and Sarcina lutea as the test organisms. The most active compounds were cholesterol derivatives containing a tertiary or quaternary nitrogen in, or attached to, the A ring. Similar methyltestosterone or progesterone derivatives were inactive. All of the cholesterol derivatives that inhibited growth were surfactant, and, structurally, they would be classified as cationic detergents. Some of the inactive compounds were surfactant, but, structurally, they would be classified as nonionic detergents. Certain features of the antibacterial activity of one of the active steroids-ND 212 (4-dimethylaminoethyl-4-aza-5-cholesten-3-one methiodide)-were studied. Growth of a culture of B. subtilis containing 5 x 10(7) cells per milliliter was inhibited by 1 mug/ml (1.7 x 10(-6)m) of ND 212. The amount of growth inhibition was directly related to both cell and steroid concentration. Loss of viability was rapid and irreversible. With B. subtilis, cell lysis was observed. With S. lutea grown in C(14)-glucose, ND 212 caused release into the media of up to 25% of the cellular radioactivity. Extensive leakage occurred before loss of viability was observed. At bacteriostatic azasteroid concentrations, there was little leakage. ND 212 was readily bound in large amounts to B. subtilis cells. Inactive azasteroids were bound poorly. C(14)-cholestanone was also bound, whereas C(14)-methyltestosterone and C(14)-progesterone were not bound in significant amounts. At least 50% of the bound C(14)-cholestanone was associated with the membrane fraction.