The etiopathogenesis of
primary biliary cirrhosis (PBC) remains speculative. Epithelioid
granulomas are often found in the vicinity of damaged interlobular bile ducts in PBC, raising the possibility of a reaction to microbial materials. In this study, we tried to detect and identify
bacterial DNA within granulomatous lesions in PBC. Using liver sections from 9 patients with PBC and 13 control livers,
granuloma in portal tracts, portal tracts without
granuloma, and adjacent hepatic parenchyma were selectively microdissected from sections, and then
DNA was extracted from them. First, part of the bacterial
16S ribosomal RNA (rRNA) gene was amplified from
DNA samples extracted from 5 PBC and 6 control livers, and their amplicons were sequenced for the identification of bacterial species. Several indigenous bacteria were identified. Among them, Propionibacterium acnes (P. acnes) was detected as a major clone in 20% to 50% of sequenced clones from
granuloma of PBC, but the detection rate of P. acnes was 0% to 20% in those cloned from adjacent hepatic parenchyma of PBC. Then, a P. acnes-specific PCR was performed using all microdissected samples. Distinct PCR products were identified in epithelioid
granuloma in all 9 PBC cases. The result that P. acnes
DNA is present as a major clone in
granulomas of PBC, suggest that P. acnes is involved in the pathogenesis of
granuloma in PBC.