In vitro photodynamic inactivation of Candida spp. by different doses of low power laser light

SummaryThis study evaluated the efficacy of PDT in photoinactivation of Candida species using methylene blue (MB) and irradiation with a diode laser (660 nm, 40 mW). Suspensions of Candida species were obtained containing 106 cfu/ml, transferred to 96-holes plates and exposed to 03 doses of laser light (60 J/cm2, 120 J/cm2, 180 J/cm2) in the presence of MB. Additional suspensions were treated with only the MB, the laser light or with 0.85% saline (control groups). After the treatments, 1 μl aliquot of the suspensions was plated in duplicate on SDA. The plates were incubated at 37 °C for 24–48 h and after this period there was the counting of colonies (cfu/ml). The three evaluated doses determined meaningful inactivation of Candida spp. (p < 0.05). The 180 J/cm2 dose was the most effective, inactivating 78% of cfu/ml. At a dose of 180 J/cm2C. albicans was the most susceptible specie. PDT has demonstrated effectiveness in the inactivation of Candida spp.