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LiquidArray® technology for the detection of extended drug resistance mutations

V Szel(1) A Orosz(1) G Papp-Bernath(1) I Man(1) Z S Gyimesi(1) D Gulyas(1) L Lorinczi(1)

1:National Reference Laboratory for Mycobacteriology, Hungary

Since 2022, the 6 month BPaL(M) regimen is endorsed by WHO for treating MDR-TB. The global uptake of the regimen has been slow due to drug availability, however the spectrum of the available susceptibility tests is expanding. Up until recently, reliable genotypic drug susceptibility testing (gDST) of new and repurposed drugs, including those used in BPaL(M), was available through sequencing. However, in most EU/EEA countries, sequencing is only available in national laboratories. The LiquidArray® MTB-XDR kit was launched in October, 2023. It is the first moderate complexity assay offering reliable reporting of resistances to linezolid (LZD) amongst other second-line drugs. The aim was to compare the performance of LiquidArray® MTB-XDR with the Xpert MTB/XDR®, the GenoType MTBDRsl ver 2.0 and the reference standard phenotypic DST (pDST) using the MGIT system. The analysis involved 31 TB isolates from the collection of the National Reference Laboratory for Mycobacteriology, Hungary. Regarding fluoroquinolone (FLQ) resistance, GenoType found 8 (25.8%), Xpert detected 7 (22.6%), and the LiquidArray® MTB-XDR showed 6 (19.4%) isolates as FLQ resistant (2 had indeterminate result). With pDST, 7 isolates were reported as FLQ resistant. Regarding amikacin (AMK) resistance, GenoType found 3 (9.7%), Xpert detected 6 (19.4%), and the LiquidArray® MTB-XDR  showed 3 (9.7%) isolates as AMK resistant. Phenotipically, 4 (12.9%) isolates were identified as AMK resistant. With regards to LZD, a total of 3 (9.7%) isolates were resistant both pheno- and genotipically. The LiquidArray® technology reliably detects a range of relevant SL drug-resistance mutations.

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