Clinical characteristics and mortality risk factors in enterococcal bloodstream infections: a 9-year retrospective...

Enterococcus species are major causative pathogens of hospital-acquired bloodstream infections (BSIs), and Enterococcus faecium exhibits high antimicrobial resistance and mortality rates. The recent increase in reported cases of vancomycin-resistant enterococci (VREs) in Japan underscores the need to monitor trends in Enterococcus infections and assess the associated clinical outcomes. We aimed to clarify the distribution and antimicrobial susceptibility trends of Enterococcus spp., clinical characteristics of patients, and risk factors associated with 30-day mortality in hospital-acquired BSIs at a university hospital.

This retrospective cohort study was conducted using data from patients diagnosed with Enterococcus BSI between January 2015 and December 2023. Trends in species distribution and susceptibility were analysed over three consecutive 3-year periods. A multi-variate Cox regression analysis was performed to identify the predictors of 30-day mortality.

E. faecium accounted for the highest proportion of isolates (55.8%), followed by Enterococcus faecalis (38.1%), with no significant change over time. Ampicillin susceptibility was 6.1% for E. faecium, significantly lower than 100% for E. faecalis. No VRE strains were detected. E. faecium infections were more frequently observed in patients with haematologic malignancies, neutropenia, and prior antibiotic exposure and were associated with a higher 30-day mortality than E. faecalis infection. In the multi-variate analysis, the Pitt Bacteremia Score, Charlson Comorbidity Index, and E. faecium infection were independent predictors of 30-day mortality.

Species distribution and antimicrobial susceptibility of Enterococcus BSIs remained stable over time. E. faecium infection was strongly associated with poor prognosis, emphasizing the importance of species-specific clinical assessments.