Biofilm formation on venovenous ECMO cannulas can lead to re-introduction of pathogens during the decannulation process – a small-scale study reveals new insights when combining cultures and molecular results

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) cannulas are potential reservoirs for pathogens, yet their role in bacteremia and sepsis following decannulation remains poorly understood. This proof-of-concept study aims to characterize bacterial colonization of ECMO cannulas, identify potential sources of these bacteria, and assess their association with post-decannulation bloodstream infections and sepsis. METHODS: We conducted a single-center observational study including 10 patients receiving venovenous ECMO support between January 2022 and January 2023. Microbial colonization of cannulas, skin sites, and plasma was analyzed using culture-based methods and 16S rDNA amplicon sequencing. Alpha and beta diversity analyses were performed, and findings were correlated with clinical outcomes, including sepsis and bacteremia. RESULTS: A total of 117 samples yielded ~ 11 million sequencing reads. Bacteria colonizing ECMO cannulas matched pathogens causing prior bacteremia during ECMO support in all affected patients. Bacteria detected on cannulas and insertion sites were frequently recovered in plasma following decannulation. Notably, 16S rDNA analysis detected circulating pathogens that conventional cultures missed, often those from prior infections that were thought to be eradicated by antibiotics. Patients who developed sepsis post-decannulation exhibited higher bacterial diversity on cannulas and a higher overall abundance of Pseudomonas, while non-septic patients had greater Enterococcus abundance. CONCLUSIONS: Our results confirm that ECMO cannulas serve as pathogen reservoirs, with decannulation enabling bacterial translocation into the bloodstream and contributing to post-decannulation sepsis. 16S rDNA sequencing exhibited greater sensitivity than cultures for detecting bloodstream pathogens. These findings support re-assessment of prophylactic measures during ECMO decannulation and lay the groundwork for developing early sepsis risk stratification tools.