P073

1:National Reference Laboratory for Mycobacteria, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal; 2:Genomics and Bioinformatics Unit, Department of Infectious Diseases, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal

Opportunistic infections caused by nontuberculous mycobacteria (NTM) have become a growing public health concern. Among these, those belonging to the Mycobacterium avium complex (MAC) are the most common etiological agents of human disease, including over ten described subspecies, with M. avium, M. intracellulare, and M. chimaera being the most common. To address the current needs in subspeciation and surveillance of MAC disease cases, we evaluated different species classification methodologies (BLASTn-based marker-gene approach, Kraken v2, rMLST and MLST databases) and their congruence with a core-SNP phylogenetic approach, based on whole genome sequencing (WGS) data. For this purpose, we used a collection of 142 MAC isolates from Portuguese patients diagnosed between 2014 and 2022. The marker-gene approach (based on the rpoB, hsp65 and groEL genes), showed the best results, allowing the identification of the 142 MAC isolates to the species/subspecies level (M. avium subsp. hominissuis, M. intracellulare, M. intracellulare subsp. chimaera, M. intracellulare subsp. yongonense, M. marseillence and M. colombiense). Using a core-SNP approach, we conducted a detailed phylogenetic analysis within each identified species group. Despite the considerable genetic diversity among MAC species, we successfully differentiated all species and subspecies and identified genetic clusters with epidemiological potential. This study highlights the importance of reliable genotyping methods for accurate species identification towards an effective management of MAC disease. Additionally, it emphasises the need for more comprehensive large-scale WGS data analysis, guided by a One Health perspective, to uncover possible transmission pathways.