Targeted Next Generation Sequencing (tNGS) for detection of drug-resistant tuberculous meningitis: Is this sequencing technology ready for prime time?

Purpose: Tuberculous meningitis (TBM) is the most severe form of tuberculosis (TB). Difficulty in diagnosing the condition along with other factors, increases its potential for high morbidity and mortality. Targeted Next Generation Sequencing (tNGS) generates high quality sequence read depths, enabling the identification of lowfrequency alleles linked to Drug resistance (DR). The paucibacillary nature of tuberculous meningitis is a challenge for making a definitive diagnosis. Methods: tNGS was performed on 20 cerebrospinal fluid (CSF) samples where, MGIT has shown Positive MTB Cultures. We simultaneously performed pyrosequencing (PSQ) and phenotypic Drug susceptibility testing (pDST) for these 20 samples. Results: Sequencing results (from tNGS and PSQ) were compared with reference standards i.e. pDST. tNGS detected MTB in 7/20 (35%) CSF samples whereas, PSQ detected MTB in 17/20 (85%). Conclusion: Although tNGS has ability to detect minority variants along with detection of additional targets than PSQ, PSQ remains the diagnostic choice in our tertiary lab.