Risk Factors for and Clinical Outcomes of Polymicrobial Bloodstream Infections.

Background: Although the clinical features of bloodstream infection are well described, the specific clinical characteristics of polymicrobial bloodstream infection have been rarely reported. The objective of this study was to examine the risk factors for and clinical outcomes of polymicrobial bloodstream infection.

Methods: A retrospective observational study was performed from January 2013 to December 2018 in a tertiary hospital. All patients with bloodstream infection were enrolled, and the data were collected from the electronic medical records.

Results: A total of 594 patients were included, 21% (126/594) of whom had polymicrobial infection. The most common copathogen was (20.81%), followed by (16.78%) and (12.08%). Compared with monomicrobial bloodstream infection, polymicrobial bloodstream infection mostly originated from the skin and soft tissue (28.6% vs. 10.5%, < 0.001). Multivariate analysis revealed that burn injury was independently associated with polymicrobial bloodstream infection (adjusted odds ratio, 3.569; 95% confidence interval, 1.954-6.516). Patients with polymicrobial bloodstream infection were more likely to have a longer hospital length of stay [40 (21, 68) vs. 27 (16, 45), < 0.001] and more hospitalization days after bloodstream infection than those with monomicrobial bloodstream infection [22 (8, 50) vs. 13 (4, 28), < 0.001]. However, no significant difference in mortality was observed between the two groups.

Conclusions: Approximately one-fifth of bloodstream infections were polymicrobial in this cohort. The main sources were skin and soft tissue infections, and burn injury was the only independent risk factor. Although mortality did not differ between the groups, considering the limitations of the study, further studies are required to assess the impact of polymicrobial (vs. monomicrobial) bloodstream infection on outcomes.