The development and evaluation of a polymerase chain reaction assay for the diagnosis of mycobacterium tuberculosis infections
The diagnosis of Mycobacterium tuberculosis by conventional techniques is associated with a number of problems which include lack of sensitivity (microscopy) and prolonged incubation periods (laboratory culture) . For these reasons various "rapid detection" methods have been developed but none of these meet all the requirements of sensitivity, specificity and rapidity. DNA probes, although rapid, only have a sensitivity similar to that of Ziehl-Neelsen stain. The polymerase chain reaction (PCR) has been shown to exhibit extreme sensitivity and specificity for a wide variety of infectious agents including virus, bacteria and protozoans. There have also been a few promising reports of PCR assays for M.tuberculosis and M.leprae. This thesis deals with the development of a PCR assay in which a repetitive 336 bp fragment is amplified from M.tuberculosis DNA. The assay is extremely sensitive (less than 10 organisms) and is entirely specific for M.tuberculosis. The assay was assessed in a comprehensive trial in which PCR was compared with conventional detection techniques in pleural fluids from 84 patients. The results of this trial demonstrate that PCR is more sensitive than laboratory culture and indicate that PCR can be used for the routine diagnosis for M.tuberculosis infections.
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