LETHAL PHOTOSENSITIZATION OF BACTERIA WITH 8-METHOXYPSORALEN TO LONG WAVE LENGTH ULTRAVIOLET RADIATION

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Abstract
Photosensitization by the furocoumarin 8-methoxypsoralen (8-MOP) of Staphylococcus aureus and Escherichia coli strains B and B/r results in markedly increased lethal action of long wave length UV radiation. The shape of the survival curves suggests a multiple event process. 8-MOP photosensitization is characterized by lack of stimulation by molecular oxygen, relation insensitivity to environmental pH, and temperature coefficients of less than 1.0 over the range 10[degree] to 45[degree]C (QlO of E. coli B = 0.67, of E. coli B/r = 0.44). These characteristics are markedly different from those of methylene blue photodynamic action with visible light. The lethality of 8-MOP photosensitization varies with the age of the bacterial culture, and with the media used prior and subsequent to exposure. Action spectrum studies have not clearly implicated 8-MOP as the primary chromogen in this system, nor has direct evidence been obtained of a cell constituent: 8-MOP complex with an absorption maximum in the long wave length UV region.