Predictors of mortality in bloodstream infections: pathogens, infection sources, and comorbidities

To identify risk factors influencing mortality in critically ill patients with bloodstream infections (BSIs). We retrospectively analyzed 2789 BSI episodes (2013–2024). Primary endpoint: 28‑day in‑hospital mortality. Source assignment used microbiological/radiological criteria. Multivariable logistic regression and Kaplan–Meier (360‑day) were applied. Among 2,789 BSI inpatients, the 28‑day in-hospital mortality was 27.4% (764/2,789). Median age was 58 years (IQR 40–71 years), male/female ratio 1.85. E. coli (31.7%), K. pneumoniae (12.2%), and S. aureus (9.1%) were predominant. MRSA accounted for 35.0% of S. aureus; ESBL‑producing E. coli 62%; carbapenem resistance rates: K. pneumoniae 5.0%, A. baumannii 85%, P. aeruginosa 11%. Cancer was present in 15.7% of patients (associated with a 28-day in-hospital mortality of 38.0%), and hematologic malignancies in 14.6% (associated with a 28-day in hospital mortality 35.7%). Urinary tract infection was the leading source (17.0%), whereas pulmonary source carried the highest 28-day in-hospital mortality (44.3%).Multivariate analysis identified independent 28-day in-hospital mortality predictors: polymicrobial infection (OR 1.54), A. baumannii (OR 2.15), Candida spp. (OR 3.80), pulmonary infection (OR 2.37), abdominal infection (OR 1.97), intracranial infection (OR 3.31), enterogenic BSIs (OR 1.75), ICU admission (OR 2.30), age > 60 years (OR 1.30), solid cancers (OR 1.79), hematologic malignancies (OR 1.57), and cerebrovascular disease (OR 1.75). The lower mortality included urinary tract source (OR 0.46) and catheter‑associated BSI (OR 0.67). Kaplan–Meier analysis (360‑day) showed 28‑day and 90‑day survival rates of 72.6% and 69.1%. BSI burden is high (27.4% 28-day in-hospital mortality) with predominance of drug‑resistant pathogens. ICU stay, malignancies, and pulmonary source increase risk, while urinary source were lower mortality. Enhanced antimicrobial stewardship and source control are urgently needed. Our study revealed a high BSI incidence (485.1 per 100,000 admissions) and a substantial 28-day in-hospital mortality (27.4%), both exceeding global benchmarks. E. coli remained the predominant pathogen (31.7%), followed by K. pneumoniae (12.2%) and S. aureus (9.1%). Antimicrobial resistance was widespread: MRSA accounted for 35.0% of S. aureus, ESBL-producing E. coli reached 62.0%, and carbapenem resistance rates were high, especially for A. baumannii (85%). Malignancies (solid tumors and hematologic malignancies) were the most common underlying conditions and were associated with 28-day mortality rates exceeding 38%. Urinary tract infection was the leading source of BSIs (14.2%), whereas pulmonary-source BSIs, though less frequent (11.9%), carried the highest 28-day mortality (44.3%). Independent predictors of 28-day mortality included polymicrobial infection, Acinetobacter baumannii, and Candida spp., pulmonary infection, abdominal infection, intracranial infection, and enterogenic BSIs, ICU admission, age > 60 years, solid cancers, hematologic malignancies, and cerebrovascular disease. Conversely, urinary tract source and catheter-associated BSIs were lower mortality. Kaplan–Meier analysis (360-day) showed a median survival of 52 days, with mortality continuing to accumulate beyond the acute phase, underscoring the need for long-term follow-up.