Abstract
The minimum lethal concentration of didecyldimethyl ammonium chloride (DDAC), a quaternary ammonium disinfectant, was 32 μg/ml against Staphylococcus aureus, but the presence of 0.7% polysorbate 80 raised it to 250 μg/ml. Viable cells were recovered from the treatment mixture at 32 μg/ml for up to 1 min when polysorbate was added, although no survivors were detected even at 20 s without polysorbate. The non-ionic surfactant depressed all the phenomena arising from the DDAC treatment including the uptake of DDAC by the cell, leakage of intracellular components, i.e. K+, 260 nm absorbing materials, and phospholipid. From these results, it is deduced that polysorbate interferes with the uptake of DDAC and also can remove the disinfectant in micelles from the cell surface, resulting in prevention of the DDAC damage to the structure and function of cell membrane.
