P053

1:University Clinic Golnik

In Slovenia between 2020 and 2021, 145 patients were newly diagnosed with pulmonary or extra-pulmonary tuberculosis. For all Mycobacterium tuberculosis (MT) isolates, WGS was performed using Illumina (San Diego, CA, USA) technology. Furthermore, for all of them drug susceptibility (pDST) results to at least first line drugs were available. pDST was performed using BACTEC MGIT 960 System (Becton Dickinson, NJ, USA).

Eight (8/145; 5.5 %) MT isolates were phenotypically resistant to at least one antibiotic. Major resistance pattern (3/8; 37.5 %) was resistance to ethionamide (ETH) and low-level resistance to isoniazid (INH) and could be explained by the presence of -15C>T mutation in fabG1 in all three cases. One case of pre-XDR tuberculosis was detected using both pDST and WGS. Majority of phenotypic resistance was confirmed with WGS. Only in one case, we observed discrepancy between pDST and WGS; MT isolate was phenotypically sensitive to INH, while using WGS -796C>T mutation in inhA was observed. In that particular case, pDST was performed with lower critical concentration (0.05 µl/ml) and isolate was tested as INH resistant. Large proportion of MT isolates (139/145; 95.86 %) belonged to lineage 4. Other lineages detected were lineage 1 (2/145; 1.38 %), lineage 2 (3/145; 2.07 %) and lineage 3 (1/145; 0.69 %).

WGS proved to be rapid and accurate tool for detecting drug resistance in clinical MT isolates.