Microbiological and Infection-Source Predictors of Mortality in Severe Sepsis Patients Undergoing Polymyxin B Hemoperfusion: A Seven-Year Real-World Cohort Study

Background: The microbiological landscape and infection-source profiles of severe sepsis in Asian ICUs differ markedly from Western cohorts and may influence the effectiveness and prognosis of adjunctive therapies such as polymyxin B hemoperfusion (PMX-HP). However, real-world data on how pathogen categories, multidrug resistance (MDR), and infection sources affect outcomes in PMX-HP-treated patients are lacking. Methods: We conducted a retrospective cohort study in a tertiary medical ICU in Taiwan, including adult patients with severe sepsis or septic shock who received PMX-HP between 2013 and 2019. Microbiological data, infection sources, MDR profiles, organ support requirements, vasoactive–inotropic score (VIS), and mortality outcomes were retrieved from electronic records. Pathogen groups (Gram-negative, Gram-positive, fungal, no-growth), MDR status, and infection sources were analyzed for associations with 28-day, ICU, and hospital mortality. Results: Among 64 patients (mean age 66.1 years; 67.2% male), Gram-negative pathogens predominated (70.3%), with Escherichia coli (31.3%) and Klebsiella pneumoniae (21.9%) being the most frequently identified organisms. MDR organisms were isolated in 26.6% of patients. The most common infection sources were pneumonia (29.7%), intra-abdominal infection (18.8%), and urinary tract infection (17.2%). Gram-negative infections were associated with higher CRRT utilization (71.9% vs. 47.1%, p = 0.04) and higher VIS at 24 h. MDR status was significantly associated with early CRRT requirement (64.7% vs. 38.6%, p = 0.048), but not with 28-day mortality (52.9% vs. 43.2%, p = 0.42). No infection source was independently associated with mortality after adjustment for APACHE II, CRRT, and VIS. Instead, greater organ failure severity—particularly renal failure requiring CRRT—was strongly associated with mortality in this cohort. Conclusions: In PMX-HP-treated severe sepsis patients, Gram-negative predominance and MDR status were associated with increased organ support requirements but were not independently associated with mortality. Outcomes were primarily associated with overall illness severity rather than microbiological category. These findings highlight the importance of combining microbiological data with dynamic physiological markers for prognostic risk stratification in Asian ICUs.