Action of a Quaternary Ammonium Disinfectant on Cell Membrane of Staphylococcus aureus

Treatment of Staphylococcus aureus cells with a quaternary ammonium disinfectant, didecyldimethyl ammonium chloride (DDAC), induced increase in turbidity of the cell suspension and inhibited the cell respiration. Addition of DDAC also increased turbidity of the suspension of protoplasts, the membrane and cytoplasm fraction, and even the liposome prepared from the cell phospholipid and soybean lecithin. In addition, it enhanced membrane fluidity of the liposome prepared from the cell phospholipid. It is proposed from findings in this and previous papers that the cationic surfactant first causes damage to the structure of the cell membrane which results in irreversible inactivation of all membrane functions.