Aim: Study the effect of laser emission in the red spectrum on growth of methicillin- sensitive. and methicillin-resistant strains of Staphylococcus aureus, as well as photodynamic effect of photosensitizer photoditazin.
Materials and methods: Effect of light of semiconduc- tor red laser (X 660 nm, 100 mW/cm2) at 30,'60, 90 and 180 J/cm2 on growth of S. aureus colonies was determined. Time of exposure 5; 10, 15 and 30 minutes. In certain series of experiments bacterial cells were sensitized in advance by a Water. solution of photoditazin at a concentration of5xl0-6 M.
Results: Red laser emission was established to cause a pronounced suppression of bacterial growth. This effect on standard S. aureus strain only took place dur- ing use of relatively high exposure doses (180 J/cm2). Photosensitivity of methicillin-resistant strain turned out to be significantly higher: bacteriostatic effect of red light was noted already at the dose of 60 J/cm2. Treatment of bacterial cells with photoditazin in advance signifi- cantly enhanced growth-inhibiting effect of laser light.