Risk factors for hospital-acquired Staphylococcus aureus bacteremia

Background: Staphylococcus aureus bacteremia (SAB) acquired in hospitals co ntinues to be a frequent and serious complication to hospitalization, and n o previous case-control studies dealing with risk factors of this severe di sease are available. Methods: Based on a 1-year prospective analysis, the data from all patients with hospital-acquired SAB admitted to 4 hospitals in Copenhagen County, D enmark, from May 1, 1994, through April 30, 1995, were evaluated. Eighty-fi ve patients with hospital-acquired SAB were matched to 85 control patients with a similar primary diagnosis at admission (matched controls). Of these, 62 patients with hospital-acquired SAB were compared with 118 other patien ts with a similar time of admission, who were randomly selected with no cli nical evidence of SAB (unmatched controls). Results: The incidence of hospital-acquired SAB was 0.71 per 1000 hospital admissions. The presence of a central venous catheter (odds ratio, 6.9; 95% confidence interval [CI], 2.8-17.0), anemia (odds ratio, 3.3, 95% CI, 1.4- 7.6), and hyponatremia (odds ratio, 3.3; 95% CI, 1.5-7.0) was significantly associated with hospital-acquired SAB in a conditional and a usual logisti c regression analysis. Nasal carriage was not an independent risk factor, b ut nasal carriers among patients in surgery (odds ratio, 4.0; 95% CI, 1.3-1 3.0) had a significantly higher risk for hospital-acquired SAB compared wit h matched and unmatched controls. The presence of hospital-acquired SAB inc reased the mortality rate 2.4-fold (95% CI, 1.1-5.2). Conclusions: The presence of a central venous catheter is an important risk factor, and hyponatremia and anemia are associated with the development of hospital-acquired SAB. Furthermore, hospital-acquired SAB in itself increa ses mortality.