The World Health Organization recommends drug-susceptibility testing of Mycobacterium tuberculosis complex for all patients with tuberculosis to guide treatment decisions and improve outcomes. Advances in whole-genome sequencing (WGS) have made it feasible to consider how this technology can aid in the assessment of drug susceptibility. Genotypic predictions of the susceptibility of M. tuberculosis to first-line drugs has been found to correlate with phenotypic susceptibility to these drugs.

The National Mycobacterium Reference Service (NMRS) performs whole genome sequencing of M. tuberculosis isolates for England. Genotypic susceptibility prediction is replacing some phenotypic testing, supported by evidence of high negative predictive value for resistance with high sensitivity and specificity prediction of pan-susceptibility to first-line drugs. Consequently, phenotypic drug susceptibility testing (pDST) is not required for approximately 70% of referred isolates. A pre-determined algorithm based on published data and local analysis is utilised at the NMRS to perform pDSTs on drug-resistant isolates and those with uncertain interpretation based on sequencing.

With the advent of new microtiter plate-based pDST for minimum inhibitory concentrations determination and WGS pipeline updates, the investigations for M. tuberculosis resistance are multifaceted and thus may seem complex.

In this session, we will discuss the common M. tuberculosis mutations, the role of genotypic and phenotypic susceptibility testing for M. tuberculosis, their essential need in infection prevention & control practices and it’s utility in public health surveillance.