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

Abstract

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.

Drug resistance of Mycobacterium tuberculosis strains in southern Brazil

“…Furthermore, as has already been demonstrated, in our population, samples from patients suspicious of having TB with a positive result by culture may actually be infected by non-M. tuberculosis species 7 . The genetic diversity among the Mycobacterium species sequences may prevent the studied genes from being amplified in PCR-SSCP.…”

“…The treated samples were then used for culture and PCR. DNA was extracted and purified as described elsewhere 7 .…”

An interdisciplinary parallel methodological approach for the diagnosis of tuberculosis in the Central state of India

“…Different methods gave different percentage of positive results (Table 1). AFB smear method with ZN staining is limited by rather poor sensitivity and a need for 5000-10000 mycobacteria per mL of sample for the results to be positive [22] -our results were no different with about 51.2% samples found positive. This method is also limited by its recognition of both M. tuberculosis and NTMs.…”

Vantagens e usos do teste rápido molecular para tuberculose: uma revisão integrativa

“…Em seguida, esta região é examinada com o objetivo de identificar mutações associadas à resistência à Rifampicina. 12,15,23 Porém, o estudo esclarece que apesar de sua capacidade de identificar mutações associadas à resistência à rifampicina, o fato de o bacilo ter a mutação não significa que ele, de fato, será resistente ao medicamento. Ademais, nem todas as cepas resistentes à Rifampicina possuem mutações na região alvo do teste.…”

“…Por isso, o uso de testes moleculares na triagem rápida de M. tuberculosis resistente não dispensa a confirmação por testes de sensibilidade. 12,23 Em estudo americano, 15 três amostras foram falso-positivas para resistência à rifampicina. Similares resultados falso-positivos também foram relatados a partir de estudos na África do Sul, incluindo o estudo de implementação FIND.…”