Polymicrobial methicillin-resistant Staphylococcus aureus bloodstream infections

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) is a serious public health concern. At times, MRSA is isolated from the blood along with other pathogens, the significance and consequences of which are not well described. This study aims to outline the clinical characteristics and outcomes of those with polymicrobial MRSA BSI compared with those with monomicrobial MRSA BSI. We conducted a retrospective case-control study of those with and without polymicrobial MRSA BSI from 2014 to 2022 at a single quaternary care center in New York City. Risk factors and outcomes for polymicrobial MRSA BSI were assessed using logistic regression analyses. Of 559 patients with MRSA BSI during the study period, 49 (9%) had polymicrobial MRSA BSI. Gram-positive Enterococcus (23%) was the most common co-pathogen. The presence of urinary (P = 0.02) and gastrointestinal (P < 0.01) devices was significantly associated with polymicrobial MRSA BSI. Polymicrobial MRSA BSI was associated with intensive care unit (ICU) admission after BSI (P = 0.01). Mortality did not differ. While polymicrobial MRSA BSI is relatively uncommon, it complicates an already complex clinical scenario of MRSA BSI.IMPORTANCEStaphylococcus aureus is a common human pathogen associated with severe disease and high mortality rates. Although clinically observed, little is known about the impact of polymicrobial staphylococcal bloodstream infection. This study evaluates polymicrobial methicillin-resistant S. aureus bloodstream infection (BSI), highlighting the increased risk of intensive care unit admission and impact on morbidity. Identifying risk factors for polymicrobial BSI, such as the presence of specific devices, can aid in early recognition and targeted interventions. Clarifying the risks and outcomes of polymicrobial infections can lead to strategies to minimize and manage these infections and explore the potential interactions between pathogens.