Circulating cytokines as markers of systemic inflammatory response in severe community-acquired pneumonia

Objectives: To assess the influence of empirical antibacterial therapy on systemic inflammatory response in patients with severe community-acquired pneumonia (CAP). Material and methods: Thirty consecutive patients with CAP meeting systemic inflammatory response syndrome (SIRS) criteria were recruited into this study. Blood samples for measurement of interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10) and C-reactive protein (CRP) concentrations were drawn on days 1, 3, 5, 7 and 10. For analysis, these patients were divided into two subgroups according to British Thoracic Society (BTS) severity score and to clinical response to the initial antibacterial therapy. Results: In the group with severe CAP (n= 15), serum concentrations of IL-6 (P = 0.0001), IL-8, (P = 0.001), IL-10 (P = 0.0001) and CRP (P = 0.0001) were significantly higher compared to patients from the non-severe group (n= 15). IL-6 presented with a sharp decrease between days 1 and 3 in non-responders with severe CAP (P = 0.004). IL-6 concentrations on day 1 were significantly associated with a response to empirical antibacterial treatment by day 3. Conclusion: Despite the absence of a clinical response to empirical antibacterial treatment as assessed by conventional clinical parameters on day 3 in patients with severe CAP meeting SIRS criteria, there was a marked reduction in the degree of the systemic inflammatory response as reflected by IL-6 levels.