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A group of nitrogen-containing steroids closely related in structure was screened for antibacterial activity, by use of Bacillus subtilisand Sarcina luteaas 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. subtiliscontaining 5 × 107cells per milliliter was inhibited by 1 μg/ml (1.7 × 10−6m) 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. luteagrown in C14-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. subtiliscells. Inactive azasteroids were bound poorly. C14-cholestanone was also bound, whereas C14-methyltestosterone and C14-progesterone were not bound in significant amounts. At least 50% of the bound C14-cholestanone was associated with the membrane fraction.

Smith, RodneyF. (University of Maryland, Baltimore), Donald E. Shay, and Norman J. Doorenbos. Antimicrobial action of nitrogen-containing steroids. J. Bacteriol. 85:1295–1299. 1963.—A new group of 16 synthetic nitrogen-containing steroids have been tested against a variety of microorganisms for antimicrobial properties. The gradient plate screening method, serial dilution, and dry weight techniques were used in the studies. The organisms tested consisted of 14 gram-negative bacteria, 10 gram-positive bacteria, 2 actinomycetes, 7 yeasts, and 8 molds. Inhibitory properties were found to be specific and potent in four compounds, with inhibitory concentrations as low as 0.37 μg/ml. Three of the active steroids are 4-aza cholestanes and one is a 4-nor-3,5-secocholestane amide. Sensitivity to the compounds was greatest in the gram-positive bacteria, followed by the yeasts and molds. The gram-negative bacteria were not inhibited. All 16 steroids interfered to some extent with pigmentation in Serratia marcescensbut not with pigment production in Pseudomonas aeruginosa. In a few instances, some of the molds were stimulated by the steroids at a concentration of 250 μg/ml.