The Intriguing Pattern of Nontuberculous Mycobacteria in Bulgaria and Description of Mycobacterium bulgaricum sp. nov.

We investigated the rise of nontuberculous mycobacteria (NTM) infections in Bulgaria, focusing on species identification and distribution from 2018 to 2022. Utilizing advanced diagnostic tools, including the Hain Mycobacterium CM/AS method, Myco-biochip assay, and whole-genome sequencing, the study identifies and characterizes a diverse range of <i>Mycobacterium</i> species from clinical samples. While <i>M. avium</i>, <i>M. gordonae</i>, <i>M. fortuitum</i>, and <i>M. chelonae</i> were dominating, a number of rare species were also found. They include such species as <i>M. marseillense</i> and <i>M. celatum</i>. Moreover, the noticeable prevalence of <i>M. terrae</i> complex species missed by conventional testing was observed. We identified a rare species, highly homologous to previously described strains from Japan; based on genome-genome distance data, we propose its reannotation as a new species. Further, a novel species was identified, which is significantly distinct from its closest neighbor, <i>M. iranicum,</i> with ANI = 87.18%. Based on the SeqCode procedure, we propose to name this new species <i>Mycobacterium bulgaricum</i> sp. nov. Dynamic changes in NTM species prevalence in Bulgaria observed from 2011 to 2022 highlight the emergence of new species and variations tied to environmental and demographic factors. This underscores the importance of accurate species identification and genotyping for understanding NTM epidemiology, informing public health strategies, and enhancing diagnostic accuracy and treatment protocols.