Duration and Persistence of Staphylococcus Aureus Bacteremia: A Prospective Cohort Study

Background: The purpose of the study was to describe and compare duration of Staphylococcus aureus bacteremia (SAB) according to methicillin resistance and primary foci of infection. We also aimed to redefine persistent SAB considering those results. Methods: We analyzed non-duplicated episodes of SAB in adult patients from three prospective SAB cohorts encompassing 14 hospitals in Korea. The duration of SAB was defined as the number of days from the administration of a susceptible antibiotic after the onset of SAB to the last day of positive blood culture for S. aureus. SAB durations were described and compared based on methicillin resistance and the primary foci of infection. The Cox proportional hazards regression was performed to explore independent risk factors for prolonged bacteremia. Cases in the top quartile for the duration of bacteremia were designated as newly-defined persistent SAB. Findings: A total of 2050 cases were analyzed. The duration of SAB was longer in methicillin-resistant SAB (MRSAB) than in methicillin-susceptible SAB (MSSAB) (median [IQR], 1 [1-3] in MSSAB vs. 1 [0-7] in MRSAB, p < 0.001). While the duration of bacteremia was shortest in the skin and soft tissue infections, they were longer in endocarditis, bone and joint, and endovascular infections, and were independently associated with those foci of infection. Newly-defined persistent SAB showed independent association with in-hospital mortality (aOR, 1.99; 95% CI, 1.54-2.58; p < 0.001). Interpretation: Durations of SAB were dependent on methicillin resistance and the primary foci of infection. The newly-defined persistent SAB is independently associated with in-hospital mortality. Funding: Seoul National University Bundang Hospital Research Fund. Declaration of Interest: None to declare. Ethical Approval: The analyses of cases from April 2015 to February 2018 were approved by the institutional review board of Seoul National University Bundang Hospital (IRB No. B-1801-442-102).