Mycobacterial DNA not detected in liver sections from patients with primary biliary cirrhosis

Recent studies in primary biliary cirrhosis have reported the detection of serum antibodies against Mycobacterium gordonae and of mycobacterial DNA in liver sections. The aim of this study was to investigate whether mycobacterial DNA is present in liver biopsy material in primary biliary cirrhosis.

Archival liver biopsy specimens from 11 patients with primary biliary cirrhosis (10 female, mean age 52 years) and 11 patients with autoimmune hepatitis (10 female, mean age 53 years) were identified. Positive control tissue comprised five archival lymph node specimens from patients with tuberculous lymphadenopathy, three of which had stained positive on ZN staining, and also a liver biopsy specimen from a patient with tuberculous hepatitis (ZN positive). Fixed sections were deparaffinised and DNA was extracted by mechanical disruption with glass beads. DNA was purified by use of diatoms and lysis in guanidinium thiocyanate in a technique previously validated for archival DNA. Primers were directed to amplify a partial 16S ribosomal RNA gene yielding the species-specific character for mycobacteria, and also to amplify the constitutively-expressed human gene GAPDH.

The polymerase chain reaction was shown to be capable of detecting 1 fg of M. gordonae DNA in 'spiked' samples, equivalent to 1-5 bacterial cells. No mycobacterial DNA was detected in liver biopsy samples from either the primary biliary cirrhosis or autoimmune hepatitis groups. Of the tuberculous control sections, mycobacterial DNA was detected in four of five lymph nodes and the liver biopsy specimen. GAPDH amplification was detected in all tested samples from liver disease and tuberculous control samples.

These data do not support a role for mycobacteria in the aetiology of primary biliary cirrhosis.