Polymicrobial bloodstream infections: A retrospective cohort study on clinical manifestations, co-infection patterns, and survival outcomes.

BACKGROUND

Polymicrobial bloodstream infections (BSI) pose a considerable diagnostic and therapeutic challenge in clinical practice due to their complex pathogenesis and wide-ranging clinical manifestations.

METHODS

We conducted a retrospective cohort study of patients with polymicrobial BSI at a tertiary hospital between 1 January 2018 and 31 May 2023 and reviewed detailed clinical data, identified infectious foci and assessed survival rates among these patients.

RESULTS

Out of 3,226 positive blood cultures, 514 (15.9 %) indicated co-infections of bacterial species. Co-infections of gram-positive cocci (GPC) and gram-negative bacilli (GNB) constituted 44.7 % (96/215) of cases, while GNB-GNB co-infections accounted for 42.3 % (91/215). The most frequent co-infection was observed between Klebsiella pneumoniae and Escherichia coli, representing 8.8 % (19/215) of cases. Notably, co-infections involving Enterococci spp. and Acinetobacter baumannii exhibited a mortality rate of 62.5 % (5/8), as did those involving Enterococci spp. and K. pneumoniae, with a mortality rate of 66.7 % (4/6). The study revealed that patients with GNB-GPC co-infections exhibited a significantly higher 15-day mortality compared to those with GNB-GNB co-infections (HR 1.8 (1.0-3.2, P = .046; log rank test, P = .037). Elevated levels of Procalcitonin (PCT) and C-reactive protein (CRP), MDR-MDR bacteria co-infections, and carbapenem-resistant Enterobacteriaceae (CRE) involvement were significantly associated with higher mortality rates of polymicrobial BSI.

CONCLUSION

The study reveals that patients presenting with hypoproteinemia and co-infections of GNB and GPC are at a higher risk of mortality. Furthermore, a significant correlation exists between survival rates and infection indices, which carries important implications for clinical diagnosis and treatment strategies.

CLINICAL TRIALS REGISTRATION NUMBER: 2024-KY-115-01.