Melting the : Nondetection of Kanamycin Resistance Markers by Routine Diagnostic Tests and Identification of New Promoter Variants.

promoter mutations can confer reduced Mycobacterium tuberculosis kanamycin susceptibility. GenoType MTBDR a widely used assay evaluating this region, wrongly classified 17/410 isolates as promoter wild type. Six out of seventeen isolates harbored mutations known to confer kanamycin resistance, and the remainder harbored either novel promoter mutations (7/11) or disputed mutations (4/11). GenoType MTBDR can miss established and new variants that cause reduced susceptibility. These data highlight the importance of reflex phenotypic kanamycin testing.