Background The prognosis for patients with severe infection is related to early treatment, including early administration of antibiotics. The study aim was to compare the short-term mortality among patients admitted with severe infection with and without systemic inflammatory response syndrome (SIRS) at arrival, and to ascertain whether the presence of SIRS might affect the timing of antibiotic administration.

Methods In this retrospective follow-up study, we included all adult patients (≥15 years) presenting to a medical emergency department in the period between September 2010 and August 2011 with a first-time admission of community-acquired severe infection (infection with evidence of organ dysfunction), with and without SIRS at arrival. The presence of SIRS was defined as two or more of the criteria according to the American College of Chest Physicians/Society of Critical Care Medicine (ACCP/SCCM) definitions. Cases were identified by manual chart review using predefined criteria of infection. Data on vital signs, laboratory values and antibiotic treatment were obtained electronically.

Results We included 1169 patients with infection and organ dysfunction, treated with antibiotics within 24 h after arrival (median age 76.1 years (IQR 63.1–83.5), 567 (48.5%) men). In all, 886 (75.8%) presented with SIRS, and 283 (24.2%) presented without SIRS. Median time to antibiotics was 4.6 h (IQR 2.9–7.0) in patients with SIRS and 6.7 h (IQR 4.5–10.3) in patients without SIRS (p<0.0001). Thirty-day mortality in patients with and without SIRS was 18.4% (95% CI 15.9% to 21.1%) and 16.6% (95% CI 12.5% to 21.5%), respectively.

Conclusions SIRS was absent in one-quarter of patients admitted with severe infection. The ‘door-to-antibiotics’ time was significantly shorter for patients with SIRS compared with patients without SIRS, but no difference was found in 30-day mortality.