Buruli ulcer caused by Mycobacterium ulcerans subsp shinshuense: a rare case of familial concurrent occurrence and detection of insertion sequence 2404 in Japan.

Importance: Buruli ulcer, a severe skin infectious disease caused by Mycobacterium ulcerans, is prevalent in tropical and subtropical areas. Recently, cases of Buruli ulcer have been increasing in Japan. All cases have been sporadic, and to date the pathogenic organism has not been detected in materials from the environment.
Observations: Three members of the same family were seen with large indurated plaques on their face and extremities in the winter of 2010. Skin biopsy specimens of their lesions showed extensive necrosis of deep dermis and subcutaneous fat. Acid-fast bacilli were detected in each biopsy specimen by Ziehl-Neelsen stain, and bacteriological analysis of cultured microorganisms revealed the strains to be M ulcerans subsp shinshuense. The patients were treated with a combination of antibiotics and surgical debridement. Insertion sequence 2404 was detected from a crayfish captured in a stagnant water channel in the backyard of the family's house.
Conclusions and Relevance: We report a rare instance of familial occurrence of Buruli ulcer in Japan. Detection of insertion sequence 2404 from a crayfish suggests that the pathogenic organism may reside in an aquatic environment in Japan, as in other endemic areas. To prevent this serious infectious disease, further investigation is needed to clarify the transmission pathway.