RT journal article T1 Identification and validation of clinical phenotypes in Staphylococcus aureus blood stream infection and their association with mortality (FEN-AUREUS cohort-based study) A1 Gutiérrez Gutiérrez, Belén A1 Gallego-Mesa, Belén A1 Kaasch, Achim J. A1 Riediger, Matthias A1 Rieg, Siegbert A1 Trigo, Marta A1 Salto-Alejandre, Sonsoles A1 Anguita-Santos, Francisco A1 Cano, Ángela A1 Prolo-Acosta, Andrea A1 López Cardenas, Salvador A1 Pérez Rodríguez, María Teresa A1 Martínez-Marcos, Francisco Javier A1 Merino-Lucas, Esperanza A1 Anaya-Baz, Blanca A1 Arizcorreta Yarza, Ana A1 Piscaglia, Marco A1 Aceituno, Alexandra A1 Romero-Calderón, Lidia A1 Hornuss, Daniel A1 Alemán-Rodríguez, Aurora A1 Gimeno-Gascón, Adelina A1 Recacha, Esther A1 Torre-Cisneros, Julián A1 Merchante, Nicolás A1 Pascual, Álvaro A1 López Cortés, Luis Eduardo A1 Rodríguez Baño, Jesús A2 Cirugía A2 Medicina K1 Bacteraemia K1 Clinical profiles K1 Mortality K1 Phenotypes K1 Staphylococcus aureus AB Background: Staphylococcus aureus bacteraemia (SAB) is heterogeneous in patients and infection-related features. The aim of the study was to identify clinical phenotypes among patients with SAB, to evaluate their association with mortality, and to derive and validate a simplified probabilistic model for phenotypes assignment. Methods: Phenotypes were derived using two-stage cluster analysis of 2128 patients from the ISAC cohort (recruited between 2013 and 2015), analysing 62 variables. Cox regression assessed phenotype–mortality associations. Logistic regression was employed to develop a simplified probabilistic model for sub-phenotype allocation, validated in two external international cohorts: INSTINCT (1217 patients, recruited between 2006 and 2011) and FEN-AUREUS (1185 patients, recruited between January 2021 and October 2024). The association between sub-phenotypes and 30-day mortality in the validation cohorts was also assessed. Findings: Cluster analysis identified three clinical phenotypes based on the probable portal of entry: A (skin and soft tissues), 458 cases; B (vascular device-associated), 573 cases; and C (other portals of entry or unknown), 1097 cases. Their 30-day mortality was significantly different (13·1%, 18·2% and 25·3%, respectively, p < 0·001). Each phenotype contained two sub-phenotypes with differing characteristics and mortality risks. Also, three phenotypes were found in the INSTINCT cohort, which clustered on the same portals of entry, with two sub-phenotypes in each. When the simplified probabilistic model was applied, the sub-phenotypes showed significant associations with 30-day mortality in both validation cohorts. In INSTINCT, the aHRs were 1·93 (A2 vs A1), 3·40 (B2 vs B1), and 3·04 (C2 vs C1). In FEN-AUREUS, the aHRs were 2·02 (A2 vs A1), 2·11 (B2 vs B1), and 2·44 (C2 vs C1). Interpretation: Patients with SAB can be classified into phenotypes and sub-phenotypes, each exhibiting considerable variations in mortality rates. To facilitate clinical application, a validated open-access algorithm and calculator for phenotype and sub-phenotype assignment have been developed, enabling their use at the time of SAB confirmation. This tool aims to support timely and personalised patient care. Funding: Instituto de Salud Carlos III, Spanish Ministry of Science, Innovation and Universities (PI21/01801). PB Elsevier Ltd SN 2589-5370 YR 2025 FD 2025-05 LK http://hdl.handle.net/10498/38159 UL http://hdl.handle.net/10498/38159 LA eng DS Repositorio Institucional de la Universidad de Cádiz RD 09-may-2026