DIFFERENT PHOTOINACTIVATION MECHANISMS IN Propionibacterium acnes FOR NEAR‐ULTRAVIOLET and VISIBLE LIGHT

Abstract

The light sensitivity of Propionibacteriurn acnes was investigated when the cells were exposed to anoxia, sodium azide, D,O or superoxide dismutase in combination with visible light (broad band red light and 415 nm) and near-ultraviolet irradiation (360 and 320 nm). During anoxia the cells became less sensitive when the irradiation wavelength increased. Oxygen increased the photodamage to a greater extent in the case of visible light than of near-UV light. The photosensitization effects were, however, more or less oxygen dependent at all wavelengths used. An effect of azide and D,O on the light sensitivity was observed for visible light, while superoxide dismutase was effective only at 320 nm.The results support the hypothesis that inactivation of P. acnes with near-UV and visible light is based on different mechanisms. Porphyrin photosensitization, accomplished by singlet oxygen, is the most important mechanism when visible light is used. At shorter wavelengths (320 and 360 nm) singlet oxygen is not involved and for 320 nm the destruction might occur via superoxide anion formation.

Light Therapy in the Treatment of Acne Vulgaris

“…Research has shown in vitro that the viability of P. acnes relates inversely to light intensity. According to an action spectrum for the inactivation of P. acnes , the sensitivity of P. acnes is highest for shorter wavelengths and decreases with increasing wavelength 25 . Interestingly, the effect of UV light on lymphocytes was found to be dose dependent: When using high density, UV light is lymphocytotoxic and can diminish inflammation; in contrast, using low‐density UV can encourage inflammatory reactions 26,27 .…”

The Response of Human Skin Commensal Bacteria as a Reflection of UV Radiation: UV-B Decreases Porphyrin Production

“…The endogenous porphyrins in P. acnes absorb light in the near UV (150–400 nm) and the visible (580–650 nm) regions [19], [20]. It has been reported that irradiation of P. acnes with blue light (400–420 nm) leads to photo-excitation of bacterial porphyrins, singlet oxygen production and eventually bacterial destruction [21].…”

Efficacy of adjunct (laser) therapy to topical agents among Southern Nigerian acne vulgaris patients

“…The effect of light on acne is very common in the literature: photosensitization of p. acne [10] anti-inflammatory effect [26] and photoinactivation of pilosebaceous gland [14,27] are few examples. On the contrary, some subjects reported that sun aggravates their pimples.…”