Exogenous coproporphyrin III production by Corynebacterium aurimucosum and Microbacterium oxydans in erythrasma lesions

Erythrasma is a superficial skin disease caused by Gram-positive Corynebacterium species. Coral-red fluorescence under Wood's light, strongly suggestive of erythrasma, can be attributed to the presence of porphyrins. Fractionated porphyrin analysis in erythrasma lesions is yet to be reported. We attempted to investigate erythrasma lesions by isolating the responsible bacteria and determining their exogenous porphyrin production by HPLC analysis. We observed a 78-year-old woman with erythrasma who had a well-demarcated slightly scaling patch on her left foot, between the fourth and fifth toes. Two kinds of colonies on 5% sheep blood agar were obtained from this lesion. Analysis of the 16S rRNA sequence revealed the colonies to be Corynebacterium aurimucosum and Microbacterium oxydans. HPLC analysis demonstrated that coproporphyrin III (Copro III) levels were clearly elevated, although the amounts of protoporphyrin were diminished. These results indicate that the fluorescent substance was Copro III. This study supports the view that excess Copro III synthesis by C. aurimucosum and M. oxydans leads to accumulation of porphyrin in cutaneous tissue, which emits a coral-red fluorescence when exposed to Wood's light.