Blue light promotes bactericidal action of plasma-activated water against Staphylococcus aureus on stainless steel surfaces

Abstract

The effects of blue light on the promotion of the bactericidal action of plasma-activated water (PAW) against Staphylococcus aureus by inducing the photolysis of staphyloxanthin (STX) were examined. A light-emitting diode (466 nm) and atmospheric-pressure plasma were applied. The degradation of STX pigments extracted through pure methanol was facilitated by increased dosage of blue light (30, 60, 90, and 150 J/cm2). After combined treatment with blue light (150 J/cm2) and PAW (10 min), the surviving population of S. aureus in liquid decreased by 2.70 log CFU/mL, which was about 40 times greater than that of single PAW treatment. Blue light (150 J/cm2) treatment induced leakage of intracellular substances, indicating potential damage to the cell membrane, which was also confirmed as an increase in the SYTOXTM green fluorescence signal. The synergistic bactericidal effect of blue light and PAW was also observed for S. aureus attached to the surface of stainless steel.