Characteristics and Risk Factors Associated with Early Mortality in Patients with Polymicrobial Bloodstream Infection: A Retrospective Clinical Study

Background and Objective Polymicrobial bloodstream infections (PBSI) in hospitalized patients are associated with increased mortality, while few studies have characterized the clinical features in this population. This study aimed to assess the risk factors and short-term prognosis of PBSI in hospitalized patients.Materials and Methods 4066 patients with culture-positive blood were included between January 1, 2015 and December 31, 2017 in the First Affiliated Hospital of Zhejiang University School of Medicine (Hangzhou, China) in our study. 218 patients were diagnosed as PBSI. The patients were divided into two groups according to the outcome after 30-day follow-up. The number of survival group were 129, while the number of non-survival group were 89. The clinical data, identified microorganisms and severity models were compared between the two groups. A cox regression model was used to identify the risk factors of 30-day mortality in PBSI patients. Five prediction models were compared by Z-test to test the value of these models to predict outcome of PBSI.Results The patients in the non-survival group were more likely to receive inappropriate antibiotic therapy at the time of PBSI and showed more severe in systemic inflammatory. They were more likely to develop to be septic shock and to be admitted in ICU than the patients in the survival group. Inappropriate initial empirical antimicrobial therapy (HR=1.713 95% CI: 1.063-2.760, p=0.027), white blood cell (HR=1.740 95% CI: 1.002-3.020, p=0.049) and platelet (HR=2.940 95% CI: 1.754-4.930, p<0.001) were independent risk factors for 30-day mortality in PBSI patients. SOFA (AUROC=0.882, 95% CI=0.832-0.922) scores was a good prognostic scoring system for predicting short-term mortality in PBSI patients. The SOFA score was more valuable than the other four models in predicting the outcome of PBSI according to the Z-test (p<0.05).Discussion and Conclusions Inappropriate initial empirical antimicrobial therapy, white blood cell and platelet were closely associated with short-term mortality.