Molecular Identification of Strains within the Complex and Determination of Resistance to Macrolides and Aminoglycosides.

One of the most relevant and pathogenic groups among the rapidly growing mycobacteria (RGM) is complex (MABC) that includes three subspecies: subsp. subsp. , and subsp. . The aim of this study was the analysis of prevalence of MABC among other non-tuberculous mycobacteria isolated from patients in the Malopolska Region of Poland, between 2018 and 2021, as well as determination of their subspecies and molecular mechanisms of resistance to macrolides and aminoglycosides. The incidence of MABC was 5,4% (12/223). Eight strains were classified as subsp. , three as subsp. and one subsp. . Molecular analysis showed resistance to macrolides for eight strains of subsp. associated with (41)T28 gene mutations. One strain of subsp. showed resistance to macrolides (two mutations simultaneously: in (41)T28 and genes) and aminoglycosides (point mutation in gene). One strain of subs. was resistant to macrolides ((41)T28 mutation), whereas presented no mutations for aminoglycosides. subsp. reveal no mutations. High clarithromycin resistance of , determines the urgent need for susceptibility-based treatment. Molecular determination of resistance mechanisms to aminoglycosides and macrolides enables fast and accurate targeted treatment implementation.