Development of a 23S rRNA-based PCR assay for the detection of mycobacteria

The partial nucleotide sequence of a recombinant plasmid containing the 23S rRNA gene of Mycobacterium tuberculosis was determined and an assay was developed for amplifying 23S rRNA gene sequences of mycobacteria. The PCR-based non-radioactive test enabled us to distinguish Mycobacterium from other closely related genera and was sensitive enough to detect 2 bacterial genome equivalents. The assay was extended to the detection of mycobacterial DNA in uncultured clinical specimens; 23S rRNA sequences were detected in thirty four of forty eight (70.8%) sputum and cerebrospinal fluid (CSF) specimens by the PCR assay, whereas direct smear examination and culture methods demonstrated a positivity rate of 29.2% and 16.7% respectively for the same specimens. A RNA-based PCR assay with a detection limit of 1 genome equivalent was also developed. These PCR assays should prove useful for the early and rapid detection of mycobacterial infection in uncultured clinical specimens.