COMPARISON OF THE ABI-7700 SYSTEM (TAQMAN) AND COMPETITIVE PCR FOR QUANTIFICATION OF IS6110 DNA IN SPUTUM DURING TREATMENT OF TUBERCULOSIS

Mycobacterium tuberculosis can persist in sputum for long periods of t ime after the initiation of antituberculosis chemotherapy, The purpose of this study was to determine whether quantitative estimates of M. t uberculosis DNA in sputum correlate with the numbers of viable bacilli and thus measure the therapeutic response of patients during treatmen t. Two methods of M. tuberculosis DNA quantification were examined by using DNA isolated from sputum specimens serially collected during the course of chemotherapy. A competitive PCR assay was compared to an au tomated system of real-time quantification with the ABI Prism 7700 Seq uence Detection System (TaqMan), The ABI 7700 system uses standard PCR in conjunction with a fluorogenic probe in which the intensity of flu orescence is proportional to the amount of target DNA present. The res ults showed that both PCR systems are reproducible and accurate. The a mounts of M. tuberculosis DNA quantified in sputum corresponded well w ith the numbers of acid-fast bacilli (AFB) counted by microscopy, Befo re initiation of antituberculosis therapy, measures of AFB, M. tubercu losis DNA, and cultivable bacilli were similar, suggesting that quanti fication of DNA is a good method for measuring the initial bacillary l oad. However, the rate of disappearance of both AFB and M. tuberculosi s DNA did not correlate with the decline in cultivable bacilli in the specimen; therefore, these tests are not appropriate for monitoring tr eatment efficacy.