We compared methylene blue (MB)-mediated photobactericidal efficacies against Pseudomonas aeruginosa when using
nanosecond pulsed light and CW light. In the intensity range of 10-200 mW/cm2, there was no significant difference
between two cases, while photobactericidal efficacy with nanosecond pulsed light was significantly lower than that with
CW light at an intensity of 250 mW/cm2. This is attributable to the saturated absorption of MB molecules due to high
peak intensity of nanosecond pulsed light. On the basis of these results, we estimated the depth dependence of bacterial
killing, showing that in the skin tissue region deeper than 1.5 mm, photobactericidal efficacy with nanosecond pulsed
light was higher than that with CW light. This suggests that the advantage of using high-peak-intensity pulsed light for
deep tissue treatment.