The Specific Organism: Not Bacterial Gram Type: Drives the Inflammatory Response in Septic Shock

Background and Hypothesis: The inflammatory response was targeted by unsuccessful therapies but ignored pathogen. We hypothesized that the inflammatory response differs according to organism in human septic shock. Materials and Methods: We measured 39 cytokines at baseline and 24 h in patients ( n = 363) in the Vasopressin and Septic Shock Trial (VASST). We compared cytokine profiles (cytokine functional class) at baseline and at 24 h by organism and used hierarchical clustering to classify cytokines according to 28-day outcomes. Results: In 363 patients, 88 and 176 patients had at least 1 species isolated from blood and other sites, respectively. Cytokine levels differed significantly according to organism: Neisseria meningitidis and Streptococcus pneumoniae had the highest (baseline and at 24 h), while Enterococcus faecalis (blood) had the lowest mean cytokine levels. N. meningitidis and Klebsiella pneumoniae had significantly higher cytokine levels at baseline versus 24 h ( p = 0.01 and 0.02, respectively); E. faecalis had significantly higher cytokine levels at 24 h versus baseline. Hierarchical clustering heat maps showed that pathogens elicited similar cytokine responses not related to the functional cytokine class. Conclusion: The organism type induces different cytokine profiles in septic shock. Specific gram-positive and gram-negative pathogens stimulated similar plasma cytokine-level patterns.