[The application of molecular biology to the diagnosis of mycobacteriosis].

The application of molecular biology techniques to the diagnosis of mycobacteriosis was evaluated. The hybridization protection assay (HPA) was found to be accurate and rapid in the identification of mycobacteria. The nested polymerase chain reaction (PCR) targeting the Pab gene was specific and sensitive enough for the rapid detection of Mycobacterium tuberculosis in clinical specimens. The overall sensitivity and specificity of the nested PCR were excellent, 97% and 92%, respectively. In addition, a novel method combining the PCR and the HPA for the rapid detection of MAC and M. tuberculosis was developed. This method was as useful as the nested PCR for M. tuberculosis above mentioned. The clinical usefulness of two commercially available mycobacteria detection kits, the MTD and the Amplicor, was evaluated and compared with that of the conventional smear and culture methods. The MTD showed the highest sensitivity, while the Amplicor showed the highest specificity. The HPA was also applied to drug susceptibility tests, which require 3 to 4 weeks by conventional methods. By this method, the results of resistance to isoniazid or rifampicin could be obtained after three days incubation. Another method for determining the drug resistance of mycobacteria is the detection of gene alterations related to the drug resistance. The deletion of the catalase-peroxidase gene related to isoniazid resistance was observed in 15% of isoniazid-resistant strains. On the other hand, point mutations in the RNA polymerase beta subunit (rpoB) gene relating to rifampicin resistance were detected in 31% of rifampicin-resistant strains by the non-radioisotope PCR-SSCP analysis.(ABSTRACT TRUNCATED AT 250 WORDS)