gram positive vs gram negative endotoxin

IL-6 has a longer half-life than TNFα and its blood levels remain elevated in the presence of various diseases. IL-6 is induced by TNF, and appears in the circulation after the initial TNF response, making it a good surrogate marker of localized TNFα activity.

Measuring blood levels of these cytokines may help in evaluating the severity and predicting the outcome in patients with sepsis. Previous studies have shown that proinflammatory cytokines (TNFα, IL-1β, IL-6, and IL-8) are elevated in patients with acute respiratory distress syndrome and septic shock. A second theory suggests that the multiorgan dysfunction and shock result from neuroendocrine dysregulation and mediators released into the bloodstream from the infected tissues circulating bacteria or endotoxin are not needed as direct stimuli for intravascular inflammation. The intravascular stimulus hypothesis posits that bacteria invade through a normal or damaged epithelium and enter the bloodstream, inducing systemic inflammatory responses (for example, increased vascular permeability, leukocyte-endothelial adhesion, and activation of complement and clotting pathways) and resulting in multiorgan failure. There is evidence to support two different theories on how GN bacteria induce harmful systemic responses. Gram-negative (GN) bacteria have often been implicated in the pathogenesis of severe sepsis and septic shock, although the exact mechanism is uncertain. Future research exploring new biomarkers and danger signals and further characterizing differences in the virulence mechanisms between Gram-negative and Gram-positive bacteria appears promising and could lead to new therapeutics and to improved clinical outcomes. These observations suggest a distinct immunopathophysiologic behavior of sepsis in patients with Gram-negative bacteremia that may influence clinical outcomes. In this study, C-reactive protein and IL-6 levels were significantly higher in Gram-negative bacteremia than in Gram-positive bacteremia.

In the previous issue of Critical Care, Abe and colleagues report results of a retrospective study that show a significantly higher incidence of Gram-negative bacteremia among adult intensive care unit patients with septic shock than in those with sepsis or severe sepsis. Gram-negative bacteremia has been associated with severe sepsis, although the exact mechanism and pathophysiological differences among bacterial species are not well understood.

Gram positive vs gram negative endotoxin