Quantitative Analysis of Mycobacterial and Propionibacterial DNA in Lymph Nodes of Japanese and European Patients with Sarcoidosis

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Abstract
The cause(s) of sarcoidosis is unknown.Mycobacteriumspp. are suspected in Europe andPropionibacteriumspp. are suspected in Japan. The present international collaboration evaluated the possible etiological links between sarcoidosis and the suspected bacterial species. Formalin-fixed and paraffin-embedded sections of biopsy samples of lymph nodes, one from each of 108 patients with sarcoidosis and 65 patients with tuberculosis, together with 86 control samples, were collected from two institutes in Japan and three institutes in Italy, Germany, and England. Genomes ofPropionibacterium acnes,Propionibacterium granulosum,Mycobacterium tuberculosis,Mycobacterium aviumsubsp.paratuberculosis, andEscherichia coli(as the control) were counted by quantitative real-time PCR. EitherP. acnesorP. granulosumwas found in all but two of the sarcoid samples.M. aviumsubsp.paratuberculosiswas found in no sarcoid sample.M. tuberculosiswas found in 0 to 9% of the sarcoid samples but in 65 to 100% of the tuberculosis samples. In sarcoid lymph nodes, the total numbers of genomes ofP. acnesorP. granulosumwere far more than those ofM. tuberculosis. P. acnesorP. granulosumwas found in 0 to 60% of the tuberculosis and control samples, but the total numbers of genomes ofP. acnesorP. granulosumin such samples were less than those in sarcoid samples.Propionibacteriumspp. are more likely thanMycobacteriaspp. to be involved in the etiology of sarcoidosis, not only in Japanese but also in European patients with sarcoidosis.