Abstract:

Objective To investigate the inhibition/killing effect of 1064-nm long pulse Nd:YAG laser on Trichophyton rubrum in vitro-the most common pathogen causing onychomycosis-and the role of oxidative stress mediated by reactive oxygen species (ROS). Methods Colonies of Trichophyton rubrum were irradiated by using 1064-nm long pulse Nd:YAG laser with various pulse numbers (7 pulses, 9 pulses, 11 pulses and 13 pulses) and other parameters were fixed. Colony areas were photographed to draw growth curves before treatment and 1, 3, 5 and 7 days after treatment and assess the minimum number of pulses with the effect of growth inhibition. The colony and spore suspension of Trichophyton rubrum were irradiated with this pulse number to compare the changes of colony morphological structure, the relative activity of the spore suspension by WST-8, and the expression level of ROS after different treatments by using DCFH-DA probe. Results Nine pulses were the minimum numbers to induce the inhibitory effect. With the increase of energy, the inhibition/killing effect of laser on Trichophyton rubrum was enhanced, while the relative vitality decreased with the increase of time, showing the laser intervention had energy and time dependence. After laser intervention, mycelia lost their normal morphological structure, and the fluorescence intensity and ROS content of the spore suspension were higher than those of the unirradiated, P=0.0157 <0.05. Conclusion The 1064-nm long pulse Nd:YAG laser could inhibit/kill Trichophyton rubrum. The oxidative stress mediated by ROS may play an important role in the treatment of onychomycosis inducing by Trichophyton rubrum with 1064-nm long pulse Nd:YAG laser.

Key words: Trichophyton rubrum, the 1064-nm long pulse Nd: YAG laser, growth curve, in vitro, ROS