Risk factors for mortality caused by Staphylococcus aureus bacteremia in cancer patients.

Introduction: Staphylococcus aureus is the cause of 11-33% of nosocomial bloodstream infections and has a complication rate close to 50%. S. aureus accounts for 31% of isolates in the Instituto Nacional de Cancerología (INC), in Bogotá, Colombia, and is the main etiological agent of bacteremia. This study describes the risk factors for mortality caused by S. aureus bacteremia in cancer patients.

Methods: This is a retrospective, analytical, observational cohort study of 267 cases of bacteremia caused by S. aureus. Data from all bacteremic patients with proven cancer were extracted, and variables were introduced in a multivariate analysis using a Cox proportional hazards model.

Results: A total of 354 bacteremic patients were identified between 2001 and 2005, and 267 patients met the specified inclusion and exclusion criteria. Among these, death was considered secondary to S. aureus infection in 31%. Independent predictors of mortality related to S. aureus bacteremia in the multivariate analysis were: severity of sepsis at onset of bacteremia (HR 6.5, 95% CI 3.1-13.6), age (HR 1.03, 95% CI 1.01-1.04), non-eradicable source of infection (HR 36.3, 95% CI 5.2-254.1), heart failure (HR 10.6; 95% CI 1.8-63.7), and primary bacteremia (HR 6.3, 95% CI 1.3-31.0).

Conclusion: Severity of sepsis at the time bacteremia was detected, a non-eradicable source of infection (including primary bacteremia), and comorbid conditions were risk factors for mortality caused by S. aureus bacteremia in cancer patients. These risk factors do not differ considerably from those of patients who do not have cancer.