This retrospective cohort was conducted at a tertiary academic medical center and evaluated patients admitted between 1 June 2012 and 19 November 2018. Patients with a positive blood culture were identified using TheraDoc®
Clinical Surveillance Software (Premier, Inc., Charlotte, NC, USA) and included if they were between the ages of 3 months and 18 years, had a blood culture positive for S. aureus
, and received at least 72 h of inpatient IV treatment. Exclusion criteria were as follows: pregnancy, death within 72 h of initial culture, hospice or palliative care, and polymicrobial bacteremia. For patients with multiple incidences of bacteremia within the study period, only the first qualifying admission was included. Data was collected using Research Electronic Data Capture (REDCap™) (Vanderbilt University, Nashville, TN, USA) [19
]. Positive cultures were identified initially using a BD BACTEC FX®
instrument (Becton Dickinson, Franklin Lakes, NJ, USA). Prior to 2016, samples demonstrating Gram-positive cocci on Gram stain were identified using biochemical testing and then confirmed using Vitek2 (bioMerieux, Durham, NC, USA). In 2016, this process was changed to include the identification of Gram-positive cocci via a Biofire FilmArray®
Blood Culture ID Panel (Salt Lake City, UT, USA), then confirmed using matrix-assisted laser desorption–ionization time-of-flight mass spectrometry with VitekMS and Vitek2 (bioMerieux, Durham, NC, USA).
The primary endpoint was the rate of 30-day readmissions for patients receiving a full course of IV treatment compared to those who received oral step-down therapy. Secondary endpoints included time to microbiological cure, infection-related length of stay, total hospital length of stay, total duration of therapy, clinical failure at 90 days, 90-day readmission rates, rates of pediatric intensive care unit (PICU) admission, attributable inpatient mortality, all-cause inpatient mortality, and rates of adverse drug reactions (ADRs).
Oral step-down treatment was defined as a transition from IV antistaphylococcal therapy to oral antistaphylococcal therapy after a minimum of 72 h of IV treatment. Community-acquired infection was defined as initial positive blood cultures that were drawn within 48 h of admission, whereas hospital-acquired infection was defined as positive cultures drawn ≥48 h after admission. Healthcare-associated infection was defined as a community-onset infection plus the presence of a medical device in situ.
Microbiological cure was defined as negative blood cultures following the initial positive culture; any further blood cultures within one week of the first negative culture were required to remain negative to confirm microbiological cure (i.e., microbiological cure was not demonstrated if clearance of one blood culture was documented, but a following culture the next day returned positive).
Clinical failure at 90 days was defined as a composite of readmission within 90 days and/or recurrence of bacteremia. Recurrence of bacteremia was defined as a new culture positive for S. aureus that was separated by at least 7 days (but no more than 30 days) from the last positive blood culture for S. aureus with at least one negative blood culture in the interim period. Reinfection was defined as a new culture positive for S. aureus that was separated by at least 30 days from the last positive blood culture for S. aureus with at least one negative blood culture in the interim period.