Differences in the Phenotype of Bacterial and Viral Sepsis—A Prospective, Multicenter, Observational Study

Sepsis is defined as a dysregulated host response to an infection, leading to life-threatening organ dysfunction. While sepsis is most commonly the result of a bacterial infection, it may also be caused by viral pathogens. The aim of this study was to describe differences in organ dysfunction patterns and inflammatory markers between bacterial and viral sepsis. In this prospective multicenter cohort study, adults meeting SEPSIS-3 criteria were recruited from four Austrian ICUs between 1 August 2021 and 1 April 2024, excluding those who were immunocompromised within the preceding 12 months. Ninety patients were enrolled, of whom 57 had bacterial and 33 viral sepsis. Inflammatory markers, including IL-6 and PCT, were higher at ICU admission in bacterial sepsis. Adjusted linear regression confirmed bacterial etiology as the only significant predictor of higher 48 h peak IL-6 and PCT values. Patients with viral sepsis typically fulfilled SEPSIS-3 criteria through respiratory and cardiovascular SOFA components, while other organ dysfunctions were less frequent. Significant differences in the phenotype of bacterial and viral sepsis were observed, characterized by distinct inflammatory profiles and differing patterns of organ dysfunction. These findings may support the improved differentiation of bacterial and viral etiologies in sepsis.