P065

1:Fundación para la Investigación Biomédica del Hospital General Universitario Gregorio Marañón; 2:Escuela de Doctorado, Universidad de Alcalá, Alcalá de Henares, Madrid, España; 3:Centro de Investigación Biomédica en Red (CIBER) de Enfermedades Respiratorias - CIBERES, Instituto de Salud Carlos III, Madrid, España; 4:Departamento de Medicina, Universidad Complutense, Madrid, España; 5:Unidad de Gestión de Laboratorios, UGMI, Complejo Hospitalario Torrecárdenas, Almería, España; 6:Servicio de Microbiología Clínica y Enfermedades Infecciosas, Hospital General Universitario Gregorio Marañón. Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, España

Nontuberculous mycobacteria (NTM) are increasingly recognized as emerging pathogens worldwide, particularly affecting individuals with chronic lung disease or immunosuppression. Gaining insight into the nature and dynamics of prolonged NTM infections is critical to improve patient management and infection control strategies.

We performed genomic analysis on 330 clinical isolates from 35 patients with prolonged NTM infections (involving 13 different NTM species, most belonging to the MAC complex, 83,3%), collected between 2008 to 2024 in Almería, Spain. Infection duration ranged from 4 months to 11 years, with 2-25 isolates per patient.

Genomic analysis allowed us to differentiate between 17 true persistent infections caused by the same strain and 5 reinfections involving different strains of the same species. Three reinfections involving different NTM species were also identified. Based on the genomic patterns identified, persistent infections were further subdivided on: (i) cases without acquisition genomic diversity (0 SNPs between the sequential isolates along the infection; (ii) linear evolution, marked by the sequential accumulation of SNVs; and (iii) divergent evolution, characterized by the emergence of SNVs along different genomic branches. A subset of 6 patients showed more complex infection dynamics, combining co-infections (involving different species and dominance) with prior patterns of persistence and/or reinfection.

Our findings underscore the need for personalized genome-informed interpretation due to the high level of intra-host diversity found in prolonged NTM infections.  Longitudinal whole-genome sequencing is essential to differentiate persistence from reinfection, a key aspect for the proper clinical management of cases and to improve our understanding of NTM diversification in real-world clinical settings.