Bloodstream infections due to multi-drug resistant bacteria in the emergency department: prevalence, risk factors and outcomes-a retrospective observational study.

Multidrug-resistant organisms (MDROs) are prevalent in patients admitted to the Emergency Department (ED) and increase the risk of inappropriate empirical antibiotic therapy. Risk stratification for MDRO infection is essential to early identify patients requiring empirical broad-spectrum antibiotic therapy, but it remains challenging for emergency physicians. This study aimed to evaluate prevalence, risk factors, and outcomes of patients admitted to the ED with a bloodstream infection (BSI) caused by MDROs. A retrospective observational study enrolling all consecutive adult patients admitted with a BSI to the ED of Niguarda Hospital, Italy, from January 2019 to December 2021 was performed. 757 patients were enrolled, 14.1% with septic shock. 156 (20%) patients had a BSI caused by MDRO: extended-spectrum beta-lactamase (ESBL) producing Enterobacterales were the most prevalent followed by methicillin-resistant Staphylococcus aureus (MRSA). Risk factors for BSI due to MDRO and specifically for ESBL were chronic renal failure (OR 2.2; 95%CI 1.4-3.6), nursing home residency (OR 4.4; 95%CI 1.9-10.2) and antibiotic therapy in the last 90-days (OR 2.6; 95%CI 1.7-4), whereas for MRSA were dialysis (OR 12.3; 95%CI 1.8-83), antibiotic therapy and/or hospital admission in the past 90-days (OR 3.6; 95%CI 1.2-10.6) and ureteral stent or nephrostomy (OR 7.8; 95%CI 1.5-40.9). Patients with BSI due to MDRO had a higher rate of inappropriate empirical antibiotic therapy (50%) and longer length of stay, but no higher in-hospital mortality. Among patients admitted to the ED with a BSI, MDROs are frequent and often associated with inappropriate empirical antibiotic therapy. Specific updated risk factors for MDRO may help clinicians to better identify patients requiring a broader antibiotic therapy in the ED, while awaiting microbiological results.