Action of diethylstilbestrol on staphylococci: further observations on the effect of resting cells.

Diethylstilbestrol (DS) has been shown to be active against staphylococci and other gram-positive bacteria but not against gram-negative microorganisms. The present study extends these findings. Standardized suspensions of (14)C-labeled Staphylococcus aureus serotypes III and IV and Shigella flexneri were prepared and exposed to pharmacological concentrations of DS (1 to 20 mug/ml) under diverse environmental conditions; the cells were removed by membrane filtration and the presence of radioactive substances in release to the supernatant fraction was followed by standard radioisotopic techniques. Controls were exposed similarly to the hormone vehicle alone (buffer containing 2% ethyl alcohol). DS at bactericidal concentrations above 6 mug/ml caused significant leakage of cellular radioactivity of S. aureus labeled with (14)C-glucose and (14)C-glutamic acid within 1 to 4 hr after exposure to DS. Maximum leakage of radioactivity occurred under anaerobic conditions at 37 C. Absorption studies of (14)C-labeled DS indicated that the affinity of S. flexneri for DS is markedly less than that of S. aureus. This might be one reason for the resistance of gram-negative bacteria to DS.