Characteristics, risk factors, and mortality determinants in patients with polymicrobial bloodstream infections

Introduction: The incidence and mortality of polymicrobial bloodstream infections (pBSIs) are increasing, yet their clinical characteristics and outcomes remain poorly understood. Methodology: A retrospective analysis was conducted on 425 patients with confirmed bloodstream infections at the First Affiliated Hospital of Chongqing Medical University between January 2022 and September 2023. Clinical data, laboratory indicators, and in-hospital mortality rates were collected and analyzed. Results: Lower respiratory tract infections were identified as the most common source of pBSIs (34.4%). The most frequent pathogen combination involved Gram-negative bacilli (GNB) and Gram-positive cocci (GPC), accounting for 32.8% of cases. Among the 257 pathogens isolated, 122 were Gram-positive bacteria (47.4%) and 130 were Gram-negative bacteria (50.6%). The most commonly isolated organisms included Escherichia coli (15.6%), Klebsiella pneumoniae (10.1%), and Enterococcus faecalis (7.0%), with a notable detection rate of coagulase-negative staphylococci (CoNS; 17.9%). Gastrointestinal tumors, invasive mechanical ventilation, intra-abdominal infections, and hospital-acquired infections were identified as independent risk factors for pBSIs. Compared to monomicrobial bloodstream infections (mBSIs), pBSIs were associated with a higher mortality rate (24% vs. 17.3%, p = 0.075) and a greater incidence of septic shock (36.8% vs. 24%, p = 0.006). Diabetes, invasive mechanical ventilation, and respiratory failure were independent predictors of mortality in pBSIs patients. Conclusions: Hospitalized patients with pBSIs are at a significantly higher risk of adverse outcomes, including mortality. Early identification and targeted management of risk factors are crucial to improving prognosis and reducing mortality in patients with pBSIs.