Performance of a real-time PCR assay for the rapid identification of Mycobacterium species

Mycobacteria cause a variety of illnesses that differ in severity and public health implications. The differentiation of Mycobacterium tuberculosis (MTB) from nontuberculous mycobacteria (NTM) is of primary importance for infection control and choice of antimicrobial therapy. The diagnosis of diseases caused by NTM is difficult because NTM species are prevalent in the environment and because they have fastidious properties. In the present study, we evaluated 279 clinical isolates grown in liquid culture provided by The Catholic University of Korea, St. Vincent's Hospital using real-time PCR based on mycobacterial rpoB gene sequences. The positive rate of real-time PCR assay accurately discriminated 100% (195/195) and 100% (84/84) between MTB and NTM species. Comparison of isolates identified using the MolecuTech REBA Myco-ID(®) and Real Myco-ID® were completely concordant except for two samples. Two cases that were identified as mixed infection (M. intracellulare-M. massiliense and M. avium-M. massiliense co-infection) by PCRREBA assay were only detected using M. abscessus-specific probes by Real Myco-ID(®). Among a total of 84 cases, the most frequently identified NTM species were M. intracellulare (n=38, 45.2%), M. avium (n=18, 23.7%), M. massiliense (n=10, 13.2%), M. fortuitum (n=5, 6%), M. abscessus (n=3, 3.9%), M. gordonae (n=3, 3.9%), M. kansasii (n=2, 2.4%), M. mucogenicum (n=2, 2.4%), and M. chelonae (n= 1, 1.2%). Real Myco-ID(®) is an efficient tool for the rapid detection of NTM species as well as MTB and sensitive and specific and comparable to conventional methods.