An improved method for the species-specific assessment of mycobacteria in routinely formalin-fixed and paraffin-embedded tissues.

A polymerase chain reaction (PCR) assay for the rapid and species-specific diagnosis of mycobacterial infections in paraffin-embedded clinical specimens was developed using oligonucleotide primers to amplify a fragment of the DNA coding for the ribosomal 16S RNA of mycobacteria. The oligonucleotide primers amplified DNA from all 14 species of mycobacteria tested. By means of a reamplification protocol, as few as one to two mycobacteria could be detected in the presence of human DNA. The method of DNA isolation and amplification was applied on sections of routinely formalin-fixed and paraffin-embedded tissues. PCR for the beta-actin gene served as a control for successful DNA isolation. Mycobacterial DNA could be detected in cases of mycobacterial infections. The mycobacterial species was determined by additional sequencing of the PCR fragment. This PCR method may be a powerful tool for the diagnosis of mycobacterial infections from histopathological material and for the assessment of those mycobacteria that cannot readily be cultured, such as Mycobacterium leprae.