Background: Despite large reductions from 2005-2012, hospital-onset methicillin-resistant Staphylococcus aureus bloodstream infections (HO MRSA BSIs) continue be a major source of morbidity and mortality.

Aim: To describe risk factors for and underlying sources of HO MRSA BSIs.

Methods: We investigated HO MRSA BSIs at eight high-burden short-stay acute care hospitals. A case was defined as first isolation of MRSA from a blood specimen collected in 2016 on hospital day ≥4 from a patient without an MRSA-positive blood culture in the 14 days prior. We reviewed case-patient demographics and risk factors by medical record abstraction. The potential clinical source(s) of infection were determined by consensus by a clinician panel.

Findings: Of the 195 eligible cases, 186 were investigated. Case-patients were predominantly male (63%); median age was 57 years (range 0-92). In the two weeks prior to the BSI, 88% of case-patients had indwelling devices, 31% underwent a surgical procedure, and 18% underwent dialysis. The most common locations of attribution were intensive care units (ICUs) (46%) and step-down units (19%). The most commonly identified non-mutually exclusive clinical sources were CVCs (46%), non-surgical wounds (17%), surgical site infections (16%), non-ventilator healthcare-associated pneumonia (13%), and ventilator-associated pneumonia (11%).

Conclusions: Device-and procedure-related infections were common sources of HO MRSA BSIs. Prevention strategies focused on improving adherence to existing prevention bundles for device-and procedure-associated infections and on source control for ICU patients, patients with certain indwelling devices, and patients undergoing certain high-risk surgeries are being pursued to decrease HO MRSA BSI burden at these facilities.