Circulating Bacterial DNA in Colorectal Cancer Patients: The Potential Role of Fusobacterium nucleatum

Intestinal dysbiosis is a major contributor to colorectal cancer (CRC) development, leading to bacterial translocation into the bloodstream. This study aimed to evaluate the presence of circulated bacterial DNA (cbDNA) in CRC patients (<i>n</i> = 75) and healthy individuals (<i>n</i> = 25). DNA extracted from peripheral blood was analyzed using PCR, with specific primers targeting <i>16S</i> rRNA, <i>Escherichia coli</i> (<i>E. coli</i>), and <i>Fusobacterium nucleatum</i> (<i>F. nucleatum</i>). High <i>16S</i> rRNA and <i>E. coli</i> detections were observed in all patients and controls. Only the detection of <i>F. nucleatum</i> was significantly higher in metastatic non-excised CRC, compared to controls (<i>p</i> < 0.001), non-metastatic excised CRC (<i>p</i> = 0.023), and metastatic excised CRC (<i>p</i> = 0.023). This effect was mainly attributed to the presence of the primary tumor (<i>p</i> = 0.006) but not the presence of distant metastases (<i>p</i> = 0.217). The association of cbDNA with other clinical parameters or co-morbidities was also evaluated, revealing a higher detection of <i>E. coli</i> in CRC patients with diabetes (<i>p</i> = 0.004). These results highlighted the importance of bacterial translocation in CRC patients and the potential role of <i>F. nucleatum</i> as an intratumoral oncomicrobe in CRC.