EVALUATION OF A POLYMERASE CHAIN REACTION-BASED UNIVERSAL HETERODUPLEX GENERATOR ASSAY FOR DIRECT-DETECTION OF RIFAMPIN SUSCEPTIBILITY OF MYCOBACTERIUM-TUBERCULOSIS FROM SPUTUM SPECIMENS

In a double-blind study, 655 sputum specimens were obtained from indiv iduals suspected of having tuberculosis and were analyzed for the pres ence of Mycobacterium tuberculosis and rifampin susceptibility with us e of a polymerase chain reaction (PCR)-based universal heteroduplex ge nerator assay (PCR/UHG-Rif). Of the specimens containing viable M. tub erculosis, 100% of the smear-positive (n = 41) and 50% of the smear-ne gative (n = 6) specimens tested positive for the organism by PCR/UHG-R if. Nineteen of 537 culture-negative specimens tested positive for M. tuberculosis by PCR/UHG-Rif and were from patients with confirmed tube rculosis who were receiving antituberculosis therapy at the time of sp ecimen collection. Thirty-five specimens contained nontuberculous myco bacteria and were negative by PCR/UHG-Rif. Genotypic evidence of rifam pin resistance in five of six culture-confirmed, rifampin-resistant is olates was obtained by PCR/UHG-Rif, yielding a sensitivity and specifi city for the assay of 83% and 98.2%, respectively. These results demon strate the feasibility of using a PCR-based assay directly on sputum s pecimens for simultaneous detection of hi. tuberculosis and rifampin s usceptibility, and they suggest that patients with smear-positive, unt reated tuberculosis and those presenting with suspected drug-resistant tuberculosis are the most appropriate groups for testing by PCR/UHG-R if.