GENUS LEVEL IDENTIFICATION OF MYCOBACTERIA FROM CLINICAL SPECIMENS BYUSING AN EASY-TO-HANDLE MYCOBACTERIUM-SPECIFIC PCR ASSAY

An easy-to-handle Mycobacterium-specific PCR assay for detection of th e presence of a wide range of mycobacterial species in clinical sample s was evaluated. The performance of the genus probe was compared with the performance of probes specific for Mycobacterium tuberculosis and Mycobacterium avium and with that of standard culture. In addition, th e utility of an internal control in monitoring amplification inhibitor s was studied. Of 545 respiratory and 325 nonrespiratory specimens (a total of 870 specimens), 58 (6.7%) showed the presence of amplificatio n inhibitors, as determined by a negative result for the internal cont rol. Of these 58 specimens, 31 (53%) were stool specimens; other mater ial, even citrate blood after lysis of erythrocytes, did not pose a pr oblem with regard to inhibition of PCR amplification. Eighty-one of th e remaining 812 specimens had a positive Mycobacterium culture result. Of these culture-positive specimens, 58 (71.6%) showed a positive res ult with the Mycobacterium genus-specific probe. Seventy-two samples h ad a positive result with the Mycobacterium-specific probe but a negat ive culture result. Of these 72 samples, 26 samples,were regarded as t rue positive, either because the M. tuberculosis-or M. avium-specific probe was also positive at the same time or because other specimens fr om the same patient taken at the same time were culture positive. The sensitivity of the Mycobacterium-specific probe was 78.5% and the spec ificity was 93.5%. This study showed that pretesting of clinical speci mens for mycobacteria to the genus level with a Mycobacterium-specific probe offers the routine clinical laboratory the possibility of detec ting tuberculous and nontuberculous mycobacteria with one test. Furthe rmore, specimens testing positive with the genus-specific probe can be immediately identified with species-specific probes.