P113

1:Servei de Microbiologia, Laboratori Clínic Metropolitana Nord. Institut de Recerca i Hospital Germans Trias i Pujol (IGTP) – Badalona, Barcelona; 2:CIBER en Epidemiología y Salud Pública (CIBERESP) – Madrid; 3:Agència de Salut Pública de Catalunya, Departament de Salut, Generalitat de Catalunya - Barcelona; 4:Tuberculosis Genomics Unit, Instituto de Biomedicina de Valencia (IBV)-CSIC – Valencia; 5:Laboratori de Referència de Catalunya – El Prat de Llobregat, Barcelona; 6:Universitat de Barcelona – Barcelona; 7:Hospital Clínic de Barcelona-ISGlobal - Barcelona; 8:CIBER en Enfermedades Infecciosas (CIBERINFEC) – Madrid; 9:Hospital Universitari Vall d'Hebron – Barcelona; 10:Programa de Prevenció i Control de la Tuberculosi de Barcelona (PPCTB); 11:Serveis Clínics – Barcelona; 12:Consorci del Laboratori Intercomarcal (CLILAB) de l'Alt Penedès, l'Anoia i el Garraf – Vilafranca del Penedès; 13:Hospital Universitari Arnau de Vilanova – Lleida; 14:Hospital Universitari de Bellvitge-IDIBELL – L'Hospitalet de Llobregat; 15:CATLAB-Centre Analítiques Terrassa AIE – Terrassa; 16:Hospital de la Santa Creu i Sant Pau – Barcelona; 17:Laboratori Clínic Territorial de Girona. Hospital Universitari de Girona Dr. Josep Trueta – Girona; 18:Àrea de Microbiologia, Servei de Laboratoris Clínics, Parc Taulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí (I3PT-CERCA), Universitat Autònoma de Barcelona – Sabadell; 19:Hospital General de Granollers - Granollers; 20:Hospital Universitari Joan XXIII – Tarragona; 21:Fundació Althaia. Hospital Sant Joan de Déu – Manresa; 22:Laboratori Fundació Hospital de Palamós – Palamós; 23:Departamento de Microbiología y Parasitología. SYNLAB Diagnósticos Globales, Laboratorio central – Barcelona; 24:Laboratorio Echevarne – Sant Cugat del Vallès; 25:CIBER en Enfermedades Respiratorias (CIBERES) - Madrid; 26:Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona – Bellaterra

Tuberculosis (TB) incidence in Catalonia has remained stable in recent years, highlighting the need to strengthen surveillance efforts. In 2022, a population-based genomic surveillance system for Mycobacterium tuberculosis complex (MTBC) was integrated into the Catalan TB Control Programme to characterise transmission patterns and monitor drug resistance. Whole-genome sequencing (WGS) of MTBC isolates was performed at the Microbiology Service of Hospital Germans Trias i Pujol using Illumina technology on cultures collected from 17 laboratories. Lineages, sublineages, and resistance-associated mutations were identified using TB-Profiler, while genomic distances (based on single nucleotide polymorphisms, SNPs) were assessed with MTBseq, excluding repetitive and resistance-related regions. Recent transmission clusters were defined as groups of ≥2 monophyletic cases within 0–5 SNPs. Between 2022 and 2024, 2,293 cultures were received, of which 1,754 met inclusion criteria. Sequencing results were obtained for 1,593 isolates (90.8%). A total of 68 (sub)lineages were identified, with L4.1.2.1 (22%), L4.3.2 (13.4%), and L4.8 (12.4%) being most prevalent. No resistance mutations were found in 82% of isolates. Monoresistance was observed in 8.5%, multidrug resistance in 1%, and pre-extensively drug-resistant TB in 0.3%. Overall, 148 recent transmission clusters were detected, comprising 32.4% of sequenced cases, with 16.9% involving resistant strains. Epidemiological links were confirmed in approximately 25% of clustered cases through contact investigations. A multidisciplinary review group has been established to prioritise and evaluate relevant clusters. These findings confirm sustained community transmission of TB in Catalonia and demonstrate the added value of genomic data to inform and enhance public health interventions.