SENSITIVITY OF PORPHYROMONAS AND PREVOTELLA SPECIES IN LIQUID-MEDIA TO ARGON-LASER

The phototoxicity of argon laser irradiation was studied in aqueous su spensions of Porphyromonas endodontalis (American Type Culture Collect ion [ATCC] 35406), Porphyromonas gingivalis (ATCC 33277), Prevotella d enticola (ATCC 33184) and two strains of Prevotella intermedia (ATCC 1 5033 and 49046), all ''black-pigmented bacteria,'' BPB, that accumulat e cellular porphyrins. Several of these species have been implicated i n the etiology of periodontal disease. Non-black-pigmented bacteria we re also studied to test the specificity of irradiation as a potential photodynamic treatment for periodontal infections. Cell suspensions we re irradiated with an argon laser at fluences of 20-200 J/cm(2). When cultured in hemin-supplemented media, ATCC 15033 was the most sensitiv e to irradiation. However, a second strain of the same species (ATCC 4 9046) was resistant. The photosensitivity of other species ranked ATCC 33277 > 35406 = 33184 = 35496. When hemin was replaced in media by he moglobin, ATCC 33277 became resistant to irradiation. Protoporphyrin I X content in BPB cells was shown not to be a major factor determining photosensitivity. Oxygen was required during irradiation for BPB speci es to be affected. Non-black-pigmented bacteria were much less sensiti ve to irradiation than BPB.