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Detection of Mycobacterium tuberculosis and resistance mutations in different sample types using FluoroType MTBDR v2. A study from Germany and Denmark.

E Svensson(1) H Ketelsen(2) D Hillemann(2)

1:International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen; 2:National and WHO Supranational Reference Laboratory for Mycobacteria, Research Centre Borstel, Borstel

Objective: The FluoroType MTBDR version 2 (FTv2) is a qualitative real-time PCR for simultaneous detection of Mycobacterium tuberculosis complex (MTBC) DNA and mutations conferring resistance to rifampicin (RIF) and isoniazid (INH). We evaluated the performance of the FTv2 assay to detect MTBC in respiratory and extrapulmonary samples in a low tuberculosis prevalence setting. In addition, we investigated the performance of the FTv2 assay to detect resistance to RIF or INH in primary samples.

Methods: 1815 fresh samples from Denmark and 445 frozen samples from Germany were tested by the FTv2 assay and compared to culture. Results were compared to phenotypic antimicrobial susceptibility testing and a composite reference DNA (CRD) comprising the HAIN MTBDR line probe assay and sequencing or whole genome sequencing. In addition, to the ability of the FTv2 assay to detect RIF and INH resistance mutations, 110 frozen samples from Sierra Leone were analysed.

Results: In detecting MTBC in sputum, the sensitivity for German samples was 0.90 (CI 0.86-0.94), and specificity was 1.00 (0.89-1.00). The corresponding values were 0.86 for Denmark (0.71-0.94) and 0.98 (0.97-0.99). As for detecting resistance mutations, the sensitivity was 0.99 (0.95-1.00) for RIF and specificity 0.96 (0.97-1.00), while for INH mutations, they were 1.00 (0.96-1.00) and 0.98 (0.95-0.99).

Conclusion: FTv2 is a reliable tool for detecting MTBC DNA in pulmonary and extrapulmonary samples and detecting high-confidence mutations for INH and RIF resistance in inhA promoter, katG, and rpoB.

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