Performance of the GenoType MTBDRplus assay (v2.0) and a new extended GenoType MTBDRsl assay (v2.0) for the molecular detection of multi- and extensively drug-resistant Mycobacterium tuberculosis on isolates primarily from Lithuania

- Performance of an extended novel mutation assay to detect second-line drug resistance.
- New extended mutation assay is a useful in determining the presence of XDR-TB.
- Molecular kanamycin resistance detection was immensely improved.

The emergence of extensively drug-resistant tuberculosis (XDR-TB) hampers infection control. To assess the performance of an extended rapid novel molecular analysis for the detection of resistance conferring mutations to fluoroquinolones (gyrA, gyrB genes) and aminoglycosides/cyclic peptides (16S rRNA rrs gene, eis promotor region) compared to phenotypic susceptibility and sequencing, 43 multidrug-resistant (MDR) and 10 susceptible clinical isolates were analyzed. Results were compared to a previous version. Molecular rifampin (rpoB gene) and isoniazid (katG gene, inhA promotor region) resistance was also analyzed. XDR-TB was confirmed in 13 (30%) MDR isolates. Molecular resistance was detected in 91% ofloxacin-, 83% aminoglycoside/cyclic peptide- and 100% kanamycin-resistant isolates. In conclusion, the novel assay is a useful supplement to phenotypic susceptibility testing in determining the presence of XDR-TB. Molecular kanamycin resistance detection was immensely improved compared to the previous version. Aminoglycoside/cyclic peptide susceptible isolates revealed eis promotor region resistance in 29%, reflecting low-level kanamycin susceptibility challenges.