Photodynamic-induced inactivation of Propionibacterium acnes

Karsten Koenig; M. Teschke; Stephen G. Eick; W. Pfister; Herbert Meyer; Karl-Juergen Halbhuber

doi:10.1117/12.308137

19 May 1998 Photodynamic-induced inactivation of Propionibacterium acnes

Karsten Koenig, M. Teschke, Stephen G. Eick, W. Pfister, Herbert Meyer, Karl-Juergen Halbhuber

Proceedings Volume 3247, Optical Methods for Tumor Treatment and Detections: Mechanisms and Techniques in Photodynamic Therapy VII; (1998) https://doi.org/10.1117/12.308137
Event: BiOS '98 International Biomedical Optics Symposium, 1998, San Jose, CA, United States

Abstract

We report on photodynamically induced inactivation of the skin bacterium Propionibacterium acnes (P. acnes) using endogenous as well as exogenous photosensitizers and red light sources. P. acnes is involved in the pathogenesis of the skin disease acne vulgaris. The skin bacterium is able to synthesize the metal-free fluorescent porphyrins protoporphyrin IX (PP) and coproporphyrin (CP) as shown by in situ spectrally-resolved detection of natural autofluorescence of human skin and bacteria colonies. These naturally occurring intracellular porphyrins act as efficient endogenous photosensitizers. Inactivation of P. acnes suspensions was achieved by irradiation with He-Ne laser light in the red spectral region (632.8 nm). We monitored the photodynamically-induced death of single bacteria using a fluorescent viability kit in combination with confocal laser scanning microscopy. In addition, the photo-induced inactivation was calculated by CFU (colony forming units) determination. We found 633 nm-induced inactivation (60 mW, 0.12 cm² exposure area, 1 hour irradiation) of 72% in the case of non-incubated bacteria based on the destructive effect of singlet oxygen produced by red light excited endogenous porphyrins and subsequent energy transfer to molecular oxygen. In order to achieve a nearly complete inactivation within one exposure procedure, the exogenous photosensitizer Methylene Blue (Mb) was added. Far red exposure of Mb-labeled bacteria using a krypton ion laser at 647 nm and 676 nm resulted in 99% inactivation.

Citation Download Citation

Karsten Koenig, M. Teschke, Stephen G. Eick, W. Pfister, Herbert Meyer, and Karl-Juergen Halbhuber "Photodynamic-induced inactivation of Propionibacterium acnes", Proc. SPIE 3247, Optical Methods for Tumor Treatment and Detections: Mechanisms and Techniques in Photodynamic Therapy VII, (19 May 1998); https://doi.org/10.1117/12.308137

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