Effect of a High-Intensity Laser on Colony Count.

This study assessed the effect of a high-intensity laser on colony count. This , experimental study was conducted on standard-strain (ATCC18804). Seventy-two samples with two different concentrations of (10 cells/mL and 10 cells/mL) were randomly assigned to three groups of control, laser and nystatin. Each group included 12 samples from each concentration. In the nystatin group, 10 cc of nystatin suspension was added to the samples and mixed for 30-60 seconds. In the laser group, the Ga-Al-Ar diode laser with a 940-nm wavelength and 2-W power was irradiated to the samples with 0.4 mm tip diameter in non-contact mode (1-mm distance) at a speed of 1 mm/s. The suspensions in the three groups were cultured on the Sabouraud dextrose agar culture medium and incubated at 37°C for 24 hours. The number of colonies was then counted and reported. The three groups were compared by ANOVA and Tukey's test (alpha=0.05). In both concentrations, the mean colony count in the nystatin group was significantly lower than that in the control (<0.05) and laser (<0.05) groups. The mean colony count in the laser group was significantly lower than that in the control group (<0.05). The high-intensity laser with a 940-nm wavelength and 2-W power in non-contact mode can significantly decrease the colony count in vitro, but its effect is lower than that of nystatin.