This study was designed to compare microscopy, culture and 3 nested Polymerase Chain Reaction (PCR) based assays using as templates either of the followings: IS6110, mtp40 or 85B-RNA in the diagnosis and treatment follow up of pulmonary tuberculosis. Sputum specimens from 250 patients clinically diagnosed to have pulmonary tuberculosis were utilized. Samples were categorized into 4 groups. Group I: Samples from 120 patients with suspected TB infection; Group II: Samples from 70 patients relapsed after treatment, Group III: Samples from 30 patients not responding to treatment and Group IV: Samples from 30 patients subjected to follow up every two months during the treatment. The results of this study revealed that PCR is equally sensitive in all groups studied. TB DNA detection by PCR is more sensitive than ZN staining when taking culture plus clinical investigations as a gold standard method. In those patients with negative ZN, negative culture but have clinical and/or radiological evidence for the disease, PCR and RT-PCR methods were able to detect TB DNA and TB RNA at sensitivities of 96 and 100%, respectively. False positives were observed in TB DNA by IS6110 PCR at the end of successful treatment (probably due to detection of DNA from dead bacilli). On the contrary, RT-PCR of 85B-RNA is more specific and sensitive method for detection of viable mycobacteria. Present data altogether indicate that amplification of mtp40 and 85B-RNA are fast, sensitive and specific methods for diagnosis and follow-up of TB infection with slightly more specificity of 85B-RNA than mtp40 DNA.
Maha A. El Demellawy , Abeer Abdel Wahab , Essam M. Emad , Kamal M. Kandeel , Ashraf A. Tabll and Mostafa K. El Awady , 2006. Sensitivity of IS6110, mtp40 and 85B-RNA Based Amplification Assays in the Diagnosis and Treatment Follow up of Pulmonary Mycobacterium tuberculosis. Journal of Biological Sciences, 6: 121-126.