Photosensitization of Bacteria by Furocoumarins and Related Compounds

Abstract

IT has been known for many years that exposure to the simultaneous presence of various dyes and visible light results in the death of bacterial cells. This effect has been found to vary with different organisms, but in general, Gram-positive bacteria appear to be more sensitive^1,2. Recently, Stainer and Cohen-Bazire³, and Dworkin and Stanier⁴ have reported that a mutant of Rhodopseudomonas spheroides devoid of carotenoid is killed on exposure to visible light, due to the photosensitizing action of endogenous chlorophyll. Photosensitization of human skin by topical application of another group of compounds, the furocoumarins, has been shown by Musajo et al. ⁵ to result in erythema, œdema, and vesicle formation on irradiation with long wave-length ultra-violet light. Fitzpatrick et al. ⁶ have demonstrated the same responses, as well as increased pigmentation, upon ingestion of the furocoumarin 8-methoxypsoralen. Photosensitization of bacteria by psoralen and related compounds is described in this communication.