Day zero quantitative mRNA analysis as a prognostic marker in pulmonary tuberculosis category II patients on treatment

Mycobacterium tuberculosis m-RNA quantitation in sputum of pulmonary tuberculosis patients before starting supervised treatment was evaluated as a surrogate for response. Sputum specimens were collected from 50 patients (DOTS category II treatment; 303 specimens, day 0 to fourth month) and 16 controls (non-tubercular lung disorders). Microscopy, reverse-transcriptase PCR and DNA-PCR were compared with culture using the BACTEC 460 system. TaqMan real-time RT-PCR quantitated the mRNA levels. RT-PCR (sensitivity, 10 organisms/mL) and culture results were concordant. mRNA declined with time and correlated with culture clearance. Thirty-nine (78%) patients were smear, culture and RT-PCR negative at 2 months of treatment. Day 0 mRNA levels had statistically significant correlation with time to culture conversion and drug resistance (p 0.041). Of seven patients with sensitive isolates but high m-RNA levels, four presented with re-infection/mixed infection later, while three presented with relapse (ninth to twentieth month). The control group specimens were negative for the above tests. M. tuberculosis mRNA in the sputum is a useful prognostic marker and its quantitation an early and reliable indicator for monitoring response, prediction of culture conversion, drug resistance, re-infection and relapse. mRNA quantitation may prove to be of great value for evaluating the response to new drugs under trial.