Pathologic Difference between Sepsis and Bloodstream Infections

Sepsis, defined as life-threatening organ failure caused by a dysregulated host response to infection, is a major cause of morbidity and mortality in hospitalized patients. Understanding the features that distinguish sepsis from bloodstream infections (and other types of infection) can help clinicians appropriately and efficiently target their diagnostic workup and therapeutic interventions, especially early in the disease course.

In this review, sepsis and bloodstream infections are both defined, with a focus on recent changes in the sepsis definition. The molecular and cellular pathways involved in sepsis pathogenesis are described, including cytokines, the coagulation cascade, apoptosis, and mitochondrial dysfunction. Laboratory tests that have been evaluated for their utility in sepsis diagnosis are discussed.

Sepsis is defined not only by the presence of an infection, but also by organ dysfunction from a dysregulated host response to that infection. Numerous pathways, including proinflammatory and antiinflammatory cytokines, the coagulation cascade, apoptosis, and mitochondrial dysfunction, help determine if a bloodstream infection (or any other infection) progresses to sepsis. Many biomarkers, including C-reactive protein, procalcitonin, and lactic acid have been evaluated for use in sepsis diagnosis, although none are routinely recommended for that purpose in current clinical practice. While some laboratory tests can help distinguish the 2, the presence of organ dysfunction is what separates sepsis from routine infections.