[Evaluations of MTD and Amplicor Mycobacterium for direct detection of Mycobacteria from clinical specimens]

MTD (GEN-PROBE AMPLIFIED MYCOBACTERIUM TUBERCULOSIS DIRECT TEST) for Mycobacterium tuberculosis, and Amplicor Mycobacterium for Mycobacteria (AMP-M. tb for M. tuberculosis, AMP-M. av for M. avium and AMP-M. in for M. intracellulare) were used for the detection of relevant Mycobacterium. Their sensitivity and specificity were evaluated. Total 244 clinical specimens including 164 sputa were examined by the above two tests. The results were compared with those obtained by the conventional methods. Of 244 samples, number of the M. tuberculosis positive samples by microscopy, cultural test, MTD and AMP-M. tb were 32, 33, 38 and 35, respectively. Among 33 culture positive samples, 25 were MTD positive and 26 were AMP-M. tb positive. Therefore, sensitivity of MTD and AMP-M. tb were 75.8% and 78.8%, and their specificity were 93.8% and 95.7%, respectively. When only sputa were used for the tests as the clinical specimens, both sensitivity of MTD and AMP-M. tb were increased to 94.4%. For MAC, positive samples of M. avium complex by culture, M. avium by AMP-M. av and M. intracellulare by AMP-M. in were 13, 16, and 8, respectively. Sensitivity and specificity of AMP-M. av/M. in were 100% and 95.2%, respectively. Clinical findings of the patients whose MTD tests were positive but negative by culture were reexamined. Three of 9 specimens were also positive in AMP-M. tb. From the records of the isolations of tubercle bacilli or other important pathogens from the other kind of clinical specimens, smear tests and patients' response to tuberculosis chemotherapy, four of 9 specimens were confirmed as true positive, three were suspected as positive, and two other specimens were false positive which might be caused by contamination. From these observations, it could be concluded that MTD and AMP-M. tb are more sensitive than conventional culture method, and MTD is more sensitive than AMP-M. tb but needs more careful treatment to avoid the contamination.