DIRECT-DETECTION OF MYCOBACTERIUM-TUBERCULOSIS IN RESPIRATORY SPECIMENS USING AN AUTOMATED DNA AMPLIFICATION ASSAY AND A SINGLE TUBE NESTEDPOLYMERASE-CHAIN-REACTION (PCR)

The performance of an automated DNA amplification assay (Roche Cobas(R ) Amplicor(TM) Mycobacterium Tuberculosis Test (aPCR) was compared wit h an in-house single tube nested polymerase chain reaction (nPCR) for the direct detection of Mycobacterium tuberculosis in respiratory spec imens. Among 385 specimens, 56 were culture positive for mycobacteria (44 positive for Mycobacterium tuberculosis and 12 positive for non-tu berculosis mycobacteria). The diagnostic sensitivities of aPCR and nPC R were 86 % and 91 % whereas a 100 % diagnostic specificity of both as says was attained. By aPCR, inhibitors were detected in 6 % of the cli nical samples. For nPCR, the usage of a new thermostable DNA polymeras e facilitated pre-PCR decontamination using uracil-N-glycosylase and ' 'hot start'' in single step procedure. The results of the study indica ted that DNA amplification assays, either manual or automated, were ra pid and specific tools for diagnosing pulmonary tuberculosis.