Bactericidal effect of pulsed 1,064 nm Nd:YAG laser light on Staphylococcus epidermidis is of photothermal origin: an in vitro study

Background and objective: The aim was to investigate the bactericidal effect of the 1,064 nm Nd:YAG laser on Staphylococcus epidermidis.

Material and methods: S. epidermidis was inoculated on agar plates and then exposed to pulsed laser light in three different modes: with an uninterrupted train of pulses, or with two different repeated cycles of fractionated trains of pulses. The agar temperature was measured directly after uninterrupted radiation.

Results: A bacterial growth inhibition area of 0.3 cm(2) and maximum temperature of approximately 80 degrees C was observed after uninterrupted radiation at 2,000 J cm(-2). The corresponding figures after an exposure of 5,000 J cm(-2) were 0.9 cm(2) and 100 degrees C, respectively. No bacterial inhibition was observed after exposure to repeated cycles of 20 seconds of radiation followed by 60 seconds of rest.

Conclusion: The antimicrobial effect of the 1,064 nm Nd:YAG laser light is caused by a photothermal rather than a photochemical effect.