Molecular analysis of genetic mutations among cross-resistant second-line injectable drugs reveals a new resistant mutation in Mycobacterium tuberculosis

Abstract

Mutations causing mono and cross-resistance among amikacin, kanamycin and capreomycin of second-line injectable drugs (SLIDs) namely are not well understood.We investigated 124 isolates of Mycobacterium tuberculosis for mutations within rrs, eis, tlyA and efflux pump (Rv1258c and Rv0194) genes involved in resistance towards SLIDs. The distribution of mutations across these genes were significantly different in strains with mono-resistance or cross-resistance. A new mutation G878A was found in rrs gene, among strains with capreomycin mono-resistant, or in strains with cross-resistance of capreomycin, kanamycin and amikacin. This mutation was associated with the Euro-American X3 lineage (P b 0.0001). Mutations in the two efflux genes Rv1258c and Rv0194 were confined to strains with only capreomycin/amikacin/kanamycin cross-resistance. Wefurther investigated the minimuminhibitory concentration of capreomycin on isolateswith newG878Amutation ranging from 8 μg/mL to 64 μg/mL. Inclusion of G878A on new molecular assays could increase the sensitivity of capreomycin resistance detection.