title: Epidemiology and outcome of Staphylococcus aureus bloodstream infection and sepsis in a Norwegian county 1996-2011: an observational study.
abstract: BACKGROUND
  Staphylococcus aureus is one of the most common and lethal causes of bloodstream infection and the incidence is increasing. We carried out a prospective observational study of patients with Staphylococcus aureus bloodstream infection and sepsis in Nord-Trøndelag county in Norway from 1996-2011. The main outcome of interest was all-cause mortality within 30 and 90 days.
  
  
  METHODS
  Positive blood cultures were registered prospectively by the microbiology laboratory and clinical variables were retrospectively registered from patients' hospital records. The severity of sepsis was assigned according to the 2001 International Sepsis Definition Conference criteria. The association between clinical characteristics and mortality was studied using logistic regression analysis, and adjusted 30- and 90-day mortality risks were estimated.
  
  
  RESULTS
  Among 373 patients, the median age was 74 years and 60.3% were male. 0.8% of the patients were diagnosed with MRSA. 29.8% of the patients developed severe sepsis and 12.9% developed septic shock. The all-cause mortality was 14.5%, 27.3% and 36.2% at 7, 30 and 90 days, respectively. Compared to patients with sepsis without organ failure (Mortality risk 13.3%, 95% CI 7.5-16.3%), the 30-day mortality risk was 3-fold higher among those with severe sepsis (39.9%, 95% CI 29.5-48.5%) and more than 4-fold higher for those with septic shock (57.3%, 95% CI 42.5-72.2%). The 30-day all-cause mortality varied by focus of infection, with the highest 30-day mortality risk among those with a pulmonary focus (42.4%, 95% CI 26.0-58.5%) and unknown focus of infection (38.7%, 95% CI 27.5-48.2%). The mortality risk did not differ between the first and second halves of the study period with a 30-day mortality risk of 27.3%, (95% CI 18.1-33.1%) for 1996-2003 versus 27.4% (95% CI 19.4-31.4%) for 2004-2011. The same pattern was seen for 90-day mortality risk.
  
  
  CONCLUSIONS
  Staphylococcus aureus bloodstream infection carries a high case fatality rate, especially among those with severe sepsis and septic shock and among those with a pulmonary or unknown focus of infection. There was no decrease in 30- or 90-day mortality risk during the study period. This underscores the importance of continuing surveillance and efforts to improve the outcome of this serious disease.
authors.affiliation: Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway. julie.paulsen@ntnu.no.|Department of Medicine, Levanger Hospital, Nord-Trøndelag Health Trust, Levanger, Norway. julie.paulsen@ntnu.no.|Faculty of Medicine, Institute of Cancer Research and Molecular Medicine, Po box 8905, N-7491, Trondheim, Norway. julie.paulsen@ntnu.no.
authors.forename: Julie
authors.initials: J
authors.lastname: Paulsen
authors.affiliation: Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway. arne.mehl@hnt.no.|Department of Medicine, Levanger Hospital, Nord-Trøndelag Health Trust, Levanger, Norway. arne.mehl@hnt.no.
authors.forename: Arne
authors.initials: A
authors.lastname: Mehl
authors.affiliation: Department of Circulation and Medical imaging, Norwegian University of Science and Technology, Trondheim, Norway. asa.askim@ntnu.no.|Clinic of Anaesthesia and Intensive Care, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway. asa.askim@ntnu.no.
authors.forename: Åsa
authors.initials: Å
authors.lastname: Askim
authors.affiliation: Department of Circulation and Medical imaging, Norwegian University of Science and Technology, Trondheim, Norway. erik.solligard@ntnu.no.|Clinic of Anaesthesia and Intensive Care, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway. erik.solligard@ntnu.no.
authors.forename: Erik
authors.initials: E
authors.lastname: Solligård
authors.affiliation: Department of Public Health, Norwegian University of Science and Technology, Trondheim, Norway. bjorn.o.asvold@ntnu.no.|Department of Endocrinology, St Olavs Hospital, Trondheim University Hospital, Trondheim, Norway. bjorn.o.asvold@ntnu.no.
authors.forename: Bjørn Olav
authors.initials: BO
authors.lastname: Åsvold
authors.affiliation: Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway. jan.k.damas@ntnu.no.|Department of Infectious diseases, St Olavs Hospital, Trondheim University Hospital, Trondheim, Norway. jan.k.damas@ntnu.no.
authors.forename: Jan Kristian
authors.initials: JK
authors.lastname: Damås
mesh_terms: D000368:Aged; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D011446:Prospective Studies; D012189:Retrospective Studies; D018805:Sepsis / Q000453:epidemiology* / Q000401:mortality; D012772:Shock, Septic / Q000382:microbiology; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000401:mortality; D013211:Staphylococcus aureus / Q000302:isolation & purification*