Whole-genome sequencing-based surveillance system for Mycobacterium tuberculosis in Portugal

Pinto, Miguel; Macedo, Rita

http://hdl.handle.net/10400.18/10619

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Authors

Pinto, Miguel

Macedo, Rita

Abstract(s)

To improve TB surveillance and diagnosis, the Portuguese National Reference Laboratory (NRL) began implementing whole-genome sequencing (WGS) for all RR/MDR-TB cases in 2019. Since 2020, this approach has been expanded to indiscriminately include all received isolates. We describe the current WGS-based surveillance system in Portugal, framed in prospective and retrospective data (n = 1171), upgraded for antimicrobial resistance (AMR) prediction and epidemiological analysis. This system relies on three main steps: QC/QA and contamination assessment, with a novel data filtering step; genotyping and AMR prediction; and dynamic SNP-based approach, maximizing variable sites under analysis. While lineage 4 was the most prevalent (84.3 %) followed by lineage 2 (9.1 %), less common EU/EEA sub-lineages (e.g., lineages 3 and 6) showcased cross-border transmissions. Molecular clusters (n = 157) displayed distinct AMR profiles and diverse possible epidemiological contexts. Among the pipeline upgrades, we highlight: i) the novel filtering step that allowed the improvement of 123 out of 128 contaminated samples; ii) tolerating missing data per site more than doubled core variable site resolution; iii) automatic maximization of shared variable sites for in-depth cluster analysis, key for consolidating genetic links in epidemiological investigation. This study highlights the importance of sustained prospective genomic surveillance towards strengthening TB management and diagnosis in Portugal.

Keywords

Tuberculosis Mycobacterium Tuberculosis Complex Antimicrobial Resistance Whole-Genome Sequencing Surveillance Bioinformatics Resistência aos Antimicrobianos Portugal