Clinical characteristics, predisposing factors and outcomes of Enterococcus faecium and Enterococcus faecalis bloodstream infection in adults: a single-center retrospective study of 294 cases

Background Enterococci are critical pathogens of hospital-acquired bloodstream infection (BSI), with E. faecalis and E. faecium as the predominant species. Their incidence has been increasing. This study compared clinical characteristics, predisposing factors, and in-hospital mortality between the two species to inform clinical management. Methods This single-center retrospective study enrolled adult patients with enterococcal BSI. Demographics, comorbidities, prior exposures, pre-existing infections, and SOFA scores were collected. Multivariable logistic regression identified factors associated with E. faecium BSI (variables with p < 0.10 in univariate analysis were entered). Risk factors for mortality were analyzed using multivariable logistic regression with BIC-based optimal subset selection in the overall cohort and each species subgroup. A clinically prespecified model was adopted for sensitivity analysis in the overall cohort. Results Of 294 enrolled patients, 185 (62.9%) had E. faecium and 109 (37.1%) had E. faecalis . The overall in-hospital mortality was 49.7%. Age ≥ 65 years (aOR = 1.71, 95% CI: 1.04–2.83, p = 0.035) and ICU admission (aOR = 1.75, 95% CI: 1.01–3.04, p = 0.045) were independently associated with E. faecium BSI. Although mortality was higher in the E. faecium group (53.0% vs. 44.0%), the difference did not reach statistical significance ( p = 0.139). Age ≥ 65 years, pneumonia, and SOFA score were independent risk factors for mortality in the overall cohort and E. faecium subgroup (all p < 0.05). Only SOFA score was significant in the E. faecalis subgroup. Enterococcal species did not show a significant association with mortality after multivariable adjustment (aOR = 1.49, 95% CI: 0.46–4.79, p = 0.501). Conclusions In adult enterococcal BSI, hospital-acquired cases predominated. E. faecium was the dominant species, with higher ICU admission rates and a greater proportion of elderly patients than E. faecalis , although no statistically significant difference in mortality was observed. In the overall cohort and both subgroups, mortality was independently associated with disease severity, while no significant association was found for species.