Epidemiology and outcome of sepsis in adult patients with Streptococcus pneumoniae infection in a Norwegian county 1993-2011: an observational study

Abstract

Background: Invasive pneumococcal disease (IPD) is responsible for significant mortality and morbidity worldwide. There are however few longitudinal studies on the changes in case fatality rate of IPD in recent years. We carried out a prospective observational study of patients with IPD in Nord Trøndelag county in Norway from 1993 to 2011 to study the clinical variables and disease outcome. The main outcome was all-cause mortality after 30 and 90 days.

Methods: Patients with positive blood cultures were registered prospectively by the microbiology laboratory and clinical variables were registered retrospectively from patients' hospital records. The severity of sepsis was assigned according to the 2001 International Sepsis Definition Conference criteria. The association between mortality and predictive factors was studied using a logistic regression model.

Results: The total number of patients was 414 with mean age of 67 years and 53 % were male. Comorbidity was assessed by the Charlson Comorbidity Index (CCI). A CCI-score of 0 was registered in 144 patients (34.8 %), whereas 190 had a score of 1-2 (45.9 %) and 80 (19.3 %) had a score ≥3. 68.8 % of the patients received appropriate antibiotics within the first 6 h. The 30-day mortality risk increased by age and was 3-fold higher for patients aged ≥80 years (24.9, 95 % CI 16.4-33.4 %) compared to patients aged <70 (8.0, 95 % CI 3.5-12.4 %). 110 patients, (26.6 %) had severe sepsis and 37 (8.9 %) had septic shock. The 30 day all-cause mortality risk for those with sepsis without organ failure was 5.4 % (95 % CI 2.7-8.0 %), 20.2 % (95 % CI 13.5-27.4 %) for those with severe sepsis and 35.0 % (95 % CI 21.6-49.0 %) for those with septic shock. The mortality risk did not differ between the first and the second halves of the study period with a 30-day mortality risk of 13.5 % (95 % CI 7.9-19.2 %) for 1993-2002 versus 11.8 % (95 % CI 8.2-15.3 %) for 2003-2011.

Conclusion: IPD carries a high mortality despite early and appropriate antibiotics in most cases. We found no substantial decrease in case fatality rate during the study period of 18 years. Older age and higher severity of disease were important risk factors for death in IPD.

Keywords: Bacteremia; Sepsis; Streptococcus pneumoniae.