Evaluation of methods for detection and identification of Mycobacterium species in patients suspected of having pulmonary tuberculosis

Tuberculosis control is a priority for the Ministry of Health policies in Brazil. In the present work, the detection of Mycobacterium tuberculosis by the Polymerase Chain Reaction (PCR) was standardized, and the laboratory diagnosis of pulmonary tuberculosis was evaluated comparing baciloscopy, culture and PCR tests. The study was carried out with 117 sputum samples from different patients suspected of having pulmonary tuberculosis, for whom physicians had ordered a baciloscopy test. Baciloscopy was performed using the Ziehl-Neelsen method, and culture was performed by incubation of treated samples in Lowenstein-Jensen's medium at 37°C for eight weeks. For PCR, DNA was amplified with a specific pair of primers to the M. tuberculosis complex, with a resulting product of 123 bp from the insertion element IS6110. Three (2.56%) samples presented a positive baciloscopy result and a positive PCR result (100% agreement), and nine (7.69%) presented Mycobacterium sp. growth in culture (P= 0.1384). Among six samples with positive results in culture, one was identified by PCR-RFLP as belonging to the M. tuberculosis complex and one was identified as a non-tuberculosis mycobacteria. Sensitivity and specificity of PCR compared to culture were 33.3% and 100%, respectively.