Comparison of smear microscopy, culture, and real-time PCR for quantitative detection of Mycobacterium tuberculosis in clinical respiratory specimens

AbstractBackground: As a rapid diagnostic technique, the real-time polymerase chain reaction (PCR) can detect Mycobacterium tuberculosis with a high sensitivity and specificity. However, further studies are needed to confirm it as a standard method. In this study, we evaluated the cyp141 gene for the detection and quantification of M. tuberculosis in respiratory specimens and compared the results with direct microscopy and culture. Methods: Sputum samples (n = 247) were collected from patients of the different provinces of Iran. DNA was extracted from clinical specimens and H37Rv strain. After measuring the standard strain DNA concentration by NanoDrop and using the Avogadro number, the DNA was diluted 6 times in order to obtain 1 × 106 to 10 template copies. A Taqman probe was designed for detection of the target in a real-time PCR using the specific primers. Results: Of 247 samples, 135 (55%) were culture-negative. Of 112 (45%) culture-positive samples, 88 were positive by both smear and culture and 24 ...