Antibiotic- and hormonally induced alterations inStaphylococcus aureus

The ability of penicillin to induce permeability changes inStaphylococcus aureus was markedly enhanced by selected gonadal steroids. Subinhibitory concentrations of penicillin and subinhibitory physiological concentrations of progesterone also acted in concert to reduce the incorporation of¹⁴C-alanine into staphylococcal mucopeptides by 18 to 21%. The minimal concentration of the antibiotic which significantly interfered with the incorporation of alanine into the staphylococcal mucopeptide was 3.30 units/ml. When progesterone was added to the system, the minimal concentration was lowered to 0.50 units/ml. The 17α-hydroxy-progesterone interfered with mucopeptide synthesis only when used in conjunction with penicillin. On the contrary, progesterone, dehydroepiandrosterone and β-estradiol exerted an additive effect in decreasing the incorporation of alanine into the staphylococcal mucopeptide. These results extend our previous studies and suggest an extracellular site of hormonal action located on the cell envelope.