Species diversity of nontuberculous mycobacteria isolated from patients in Irkutsk Region (a retrospective study)

Abstract

Background. The Irkutsk Region remains a region with a high burden of multidrug-resistant tuberculosis and a challenging epidemiological situation regarding HIV infection. For immunocompromised individuals, the spread of nontuberculous mycobacteria (NTMB) poses a significant threat, as they cause pulmonary mycobacteriosis – a condition that mimics tuberculosis but requires differential diagnosis and distinct treatment approaches. Regional studies on NTMB prevalence remain limited. Given the low resolution of standard microbiological techniques, the search for molecular targets for NTMB species identification is essential. Aim. To evaluate the species diversity of NTMB isolated from patients with suspected pulmonary tuberculosis and mycobacteriosis in the Irkutsk Region. Materials and methods. A retrospective analysis was performed on NTMB strains obtained from 63 patients treated at the Irkutsk Regional Clinical Tuberculosis Hospital between 2018 and 2024. Species identification was performed for 50 isolates using sequencing of the 23S rRNA and groEL2 genes fragments, followed by phylogenetic analysis. Results. Representatives of the Mycobacterium avium complex (MAC) dominate among the studied strains (65.9%), including M. avium (53.7%) and M. intracellulare (12.2%). Joint analysis of the 23S rRNA and groEL2 gene fragments ensured the differentiation of species within the MAC, as well as the identification of a wide range of slowly and rapidly growing NTMB (M. paragordonae, M. abscessus, M. fortuitum, M. holsaticum, and M. farcinogenes/M. senegalense) and non-mycobacterial pathogens (Nocardia farcinica, Streptococcus oralis, Staphylococcus epidermidis, Actinomadura sp.). Conclusion. The taxonomic spectrum of NTMB isolated in the Irkutsk Region was characterized over time. Sequencing of the 23S rRNA and groEL2 genes allows overcoming the challenge of NTMB identification.