Effect of Butylated Hydroxyanisole on the Cytoplasmic Membrane of Staphylococcus aureus Wood 46

The antimicrobial mode of action of the phenolic antioxidant butylated hydroxyanisole (BHA) against Staphylococcus aureus Wood 46 was examined. The compound was taken up very rapidly by the cells and adsorption was completed within 15 min. Exposure of a growing suspension to 50 μg of BHA/ml was bactericidal, but this concentration had no significant effect on the viability of a non-growing suspension. However, concentrations over 100 μg/ml were lethal to the latter and this bactericidal activity was related to leakage of nucleotides. Protoplasts produced by lysostaphin treatment undergo lysis when exposed to concentrations as low as 25 μg/ml. A mutant resistant to 50 μg of BHA/ml adsorbed the same amount of BHA but protoplasts from this strain were less susceptible to lysis. It was concluded that BHA is a member-active agent.