Use of a Whole Genome Sequencing-based approach for Mycobacterium tuberculosis surveillance in Europe in 2017-2019: an ECDC pilot study.

Whole genome sequencing (WGS) can be used for molecular typing and characterisation of complex (MTBC) strains. We evaluated the systematic use of a WGS-based approach for MTBC surveillance involving all European Union/European Economic Area (EU/EEA) countries and highlight the challenges and lessons learned to be considered for the future development of a WGS-based surveillance system.WGS and epidemiological data of patients with rifampicin (RR) and multi-drug resistant (MDR)-tuberculosis (TB) were collected from EU/EEA countries between January 2017 and December 2019. WGS-based genetic relatedness analysis was performed using a standardised approach including both core genome multilocus sequence typing (cgMLST), and single nucleotide polymorphism (SNP)-based calculation of distances on all WGS data that fulfilled minimum quality criteria to ensure data comparability.From 25 countries, 2218 RR/MDR-MTBC isolates were collected. Fifty-six cross-border clusters with increased likelihood of recent transmission (≤5 SNPs distance) comprising a total of 316 RR/MDR-MTBC isolates were identified. The cross-border clusters included between two and thirty resistant isolates from two to six countries unravelling different RR/MDR-TB transmission patterns in Western and Eastern EU.This pilot study shows that a WGS-based surveillance system is not only feasible but can efficiently elucidate the dynamics of in-country and cross-border RR/MDR-TB transmission across EU/EEA countries. Lessons learned from this study highlight how the establishment of an EU/EEA centralised WGS-based surveillance system for TB will require strengthening of national integrated systems performing prospective WGS surveillance and the development of clear procedures to facilitate international collaboration for the investigation of cross-border&nbsp;clusters.</p

The 2021 WHO catalogue of Mycobacterium tuberculosis complex mutations associated with drug resistance: A genotypic analysis.

BACKGROUND: Molecular diagnostics are considered the most promising route to achieving rapid, universal drug susceptibility testing for Mycobacterium tuberculosiscomplex (MTBC). We aimed to generate a WHO endorsed catalogue of mutations to serve as a global standard for interpreting molecular information for drug resistance prediction. METHODS: A candidate gene approach was used to identify mutations as associated with resistance, or consistent with susceptibility, for 13 WHO endorsed anti-tuberculosis drugs. 38,215 MTBC isolates with paired whole-genome sequencing and phenotypic drug susceptibility testing data were amassed from 45 countries. For each mutation, a contingency table of binary phenotypes and presence or absence of the mutation computed positive predictive value, and Fisher's exact tests generated odds ratios and Benjamini-Hochberg corrected p-values. Mutations were graded as Associated with Resistance if present in at least 5 isolates, if the odds ratio was >1 with a statistically significant corrected p-value, and if the lower bound of the 95% confidence interval on the positive predictive value for phenotypic resistance was >25%. A series of expert rules were applied for final confidence grading of each mutation. FINDINGS: 15,667 associations were computed for 13,211 unique mutations linked to one or more drugs. 1,149/15,667 (7·3%) mutations were classified as associated with phenotypic resistance and 107/15,667 (0·7%) were deemed consistent with susceptibility. For rifampicin, isoniazid, ethambutol, fluoroquinolones, and streptomycin, the mutations' pooled sensitivity was >80%. Specificity was over 95% for all drugs except ethionamide (91·4%), moxifloxacin (91·6%) and ethambutol (93·3%). Only two resistance mutations were classified for bedaquiline, delamanid, clofazimine, and linezolid as prevalence of phenotypic resistance was low for these drugs. INTERPRETATION: This first WHO endorsed catalogue of molecular targets for MTBC drug susceptibility testing provides a global standard for resistance interpretation. Its existence should encourage the implementation of molecular diagnostics by National Tuberculosis Programmes. FUNDING: UNITAID, Wellcome, MRC, BMGF