Nosocomial bloodstream infections in a Finnish tertiary care hospital: a retrospective cohort study of 2175 episodes during the years 1999-2001 and 2005-2010

Background: Nosocomial infections are major causes of morbidity in hospitalized patients. Methods: Retrospective laboratory-based surveillance during 1999-2001 and 2005-2010 identified 2175 cases of nosocomial bloodstream infections (BSIs) in Tampere University Hospital (TAUH), Finland. Results: Analysis revealed that 57% of BSIs were caused by a gram-positive organism, 27% by a gram-negative organism, 5% by a fungal organism, and 11% were polymicrobial. The most common cause of nosocomial BSI was coagulase-negative staphylococci (23%). Candida species caused 5% of the infections. The 7-day and 30-day case fatalities were 8% (161/2158) and 15% (313/2175), respectively, and were highest in BSIs caused by Candida albicans (22% and 44%) and Pseudomonas aeruginosa (17% and 25%). The median age of patients was 54 years in 1999-2001, 57 years in 2005-2007, and 60 years in 2008-2010 (p < 0.001). The median time from hospital admission to the onset of BSI was 11 days (quartiles 5-18 days). This period was shortest for Streptococcus agalactiae BSI and longest for Candida non-albicans fungemia (1 vs 19 days). The case fatality rate in nosocomial BSI decreased during the years studied: 7-day and 30-day case fatalities were 9% and 16% during 1999-2001, 8.5% and 16% during 2005-2007, and 5% and 12% during 2008-2010, respectively (p < 0.003 and p = 0.022, respectively). Conclusions: Gram-positive infections predominate in nosocomial BSIs. The median age of patients with nosocomial BSI has risen during the study years. The case fatality associated with nosocomial BSI has decreased.