Evaluating the effectiveness of anti-tuberculosis treatment by detecting Mycobacterium tuberculosis 85B messenger RNA expression in sputum.

BACKGROUND: The antigen 85 complex (85B) is secreted in large quantities from growing mycobacteria and the presence of bacterial mRNA is an indicator of cell viability. The quantitative detection of 85B mRNA expression levels can be used to assess the success of anti-tuberculosis treatment outcomes to detect viable mycobacteria cells. Therefore, we evaluated the levels of 85B mRNA of Mycobacterium tuberculosis strains in patients with pulmonary tuberculosis. METHODS: Thirty patients with primary tuberculosis were included in this study. The sputum specimens of patients were collected on days 0, 15, and 30 days and were cultured and evaluated by 85B mRNA-based RT-qPCR. RESULTS: Overall, 23 of the studied tuberculosis strains were susceptible to the primary anti-tuberculosis antibiotics used in this study, 7 were resistant. By the 30th day of treatment, 85B mRNA was detected in only one of the susceptible strains, but in all 7 of the resistant strains, though the relative gene expression varied between the strains. This difference between the susceptible and resistant strains at day 30 was statistically significant (p < 0.05). CONCLUSION: 85B mRNA expression levels could be used to follow up on primary tuberculosis cases. 85B mRNA seems to be a good diagnostic marker for monitoring anti-tuberculosis treatment outcomes.

Diagnostic performance of the RT-qPCR method targeting 85B mRNA in the diagnosis of pulmonary Mycobacterium tuberculosis infection.

BACKGROUND: Several nucleic acid amplification techniques (IS6110, 16S rRNA, and 85B mRNA) were developed for the rapid, direct detection of Mycobacterium tuberculosis. We aimed to assess the diagnostic performance of 85B mRNA-based RT-qPCR by comparing with the real-time PCR COBAS TaqMan MTB Kit while using the BACTEC MGIT 960 method as the gold standard. METHODS: 60 patients with confirmed pulmonary TB and 60 individuals without TB were included as the study and control groups, respectively. Sputum specimens were cultured using LJ and BACTEC MGIT 960 systems. Extracted DNA was used for COBAS PCR in a CONAS TaqMan 48 analyzer. 85B mRNA detection was performed by RT-qPCR. RESULTS: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of COBAS TaqMan MTB Test were detected as 93.3%, 83.3%, 84.8%, 92.6%, and 88.3%, respectively. The same diagnostic parameters of RT-qPCR were: 98.3%, 95.0%, 95.2%, 98.3%, and 96.7%, respectively. According to the binary logistic regression analysis, RT-qPCR (OR: 19,924, p<0.001) was identified as the more optimal test. CONCLUSION: RT-qPCR targeting the 85B gene of M. tuberculosis seems to be a more useful and rapid technique than DNA-based methods for detecting live M. tuberculosis bacilli from sputum specimens.