Identifying the underlying causes of hospital-onset Staphylococcus aureus bacteremia: A retrospective analysis

Abstract

BACKGROUND Laboratory-based reporting of hospital-onset (HO) Methicillin-Resistant Staphylococcus aureus (MRSA) bacteremia is used by regulatory agencies as a method to decrease the incidence of MRSA bacteremia in acute care settings. Although decolonization, hand hygiene, and isolation strategies are used, many facilities continue to have high rates of HO-MRSA. To better understand the potential risk factors and underlying causes of patients developing a HO-MRSA bacteremia, a chart review of patients that developed a HO Staphylococcus aureus (SA) and meeting defined criteria was reviewed to identify potential strategies towards prevention efforts. METHODS Laboratory data was pulled from January 2016 – July 2017. Data included in the export were all positive blood cultures that grew MSSA and MRSA. The data was further filtered to only include first incident blood cultures growing MSSA or MRSA that occurred on or after the fourth day of hospitalization. Chart review was performed to identify risk factors and clinical syndromes that could potentially lead to a HO-SA bacteremia. RESULTS We identified 130 inpatients with HO-SA bacteremia, of which 63 (48%) was HO-MRSA. The most common sources identified for patients with these bacteremias were pneumonia (27%), vascular devices (20%), and skin/soft tissue infections (23%). There was no significant difference in the distribution of these sources comparing HO-MRSA with HO-MSSA. A total of 42 (32%) patients were identified to have signs and symptoms consistent with infection on admission but did not have a blood culture collected on or after day 4 of admission. Of these 42 patients, 33 (79%) were admitted from the ED and 20 (48%) are immunosuppressed patients. CONCLUSIONS Pneumonia was the most common cause of HO-SA bacteremia. Strategies to prevent HO-MRSA should include processes to prevent hospital acquired pneumonia with prompt blood culture collection on admission in patients presenting with compatable signs and symptoms.