Purpose: Although the enterococcal bloodstream infections (EBSI) are often observed in clinic, the mixed-EBSI are few reported. The aim of this study was to investigate the clinical characteristics and risk factors of mixed-EBSI in comparison with monomicrobial EBSI (mono-EBSI).
Methods: A single-center retrospective observational study was performed between Jan 1, 2013 and Dec 31, 2018 in a tertiary hospital. All patients with EBSI were enrolled, and their data were collected by reviewing electronic medical records.
Results: A total of 451 patients with EBSI were enrolled including 157 cases (34.8%) with mixed-EBSI. The most common co-pathogens were Coagulase-negative Staphylococcus  (26.86%), followed by Acinetobacter baumannii  (23.43%) and Klebsiella pneumoniae  (8.57%). In multivariable analysis, burn injury (adjusted odds ratio [aOR], 7.39; 95% confidence interval [CI], 2.69–20.28), and length of prior hospital stay (aOR, 1.01; 95% CI, 1.00–1.02) were associated with mixed-EBSI. Patients with mixed-EBSI developed with more proportion of septic shock (19% vs. 31.8%, p=0.002), prolonged length of intensive care unit (ICU) stay [9(0,25) vs. 15(2.5,36), p<0.001] and hospital stay [29(16,49) vs. 33(18.5,63), p=0.031]. The mortality was not significantly different between mixed-EBSI and mono-EBSI (p=0.219).
Conclusion: A high rate of mixed-EBSI is among EBSI, and Acinetobacter baumannii  is the second predominant co-existed species, except for Coagulase-negative Staphylococcus . Burn injury and length of prior hospital stay are independent risk factors for mixed-EBSI. Although the mortality is not different, patients with mixed-EBSI might have poor outcomes in comparison with mono-EBSI, which merits more attention by physicians in the future.
Keywords: bloodstream infections, mixed-enterococcal bloodstream infections, monomicrobial enterococcal bloodstream infections, clinical characteristics, risk factors