Community acquired bacteremia in older adults: International and prospective infectious diseases-international research initiative (ID-IRI) study

Abstract

Objectives Community-acquired bloodstream infections (CA-BSIs) are a major cause of mortality in older adults, yet prospective international data are limited. This study evaluated clinical features, microbiology, and mortality predictors in older patients with CA-BSI. Methods This prospective, observational study was conducted in 72 referral centers across 16 countries between June 1 and September 1, 2024. Patients aged ≥65 years with confirmed CA-BSI were included. Demographic, clinical, laboratory, and treatment data were collected. The primary outcome was 30-day all-cause mortality. Univariate and multivariate logistic regression was used to identify predictors. Results 574 patients were enrolled (median age 74 years; 48.1% female), and 30-day mortality was 26.3%. Urinary tract infection was the most common source (33.7%), and 30.5% had no identifiable origin. Gram-negative organisms predominated (58.6%). Independent mortality predictors included SOFA score ≥5, thrombocytopenia (<50,000/µL), Staphylococcus aureus bacteremia, pneumonia, bacteremia of unknown origin, and higher Charlson Comorbidity Index. Higher Katz Activities of Daily Living scores were protective. Conclusion CA-BSI in older adults is associated with high mortality. Outcomes are driven by comorbidity burden, functional status, infection severity, and causative pathogen, highlighting the need for early risk stratification and tailored management.