The study investigates the microbiota of colorectal cancer patients post surgery

The colonic microbiome has been implicated in the pathogenesis of colorectal cancer (CRC) and intestinal microbiome alterations are not confined to the tumor. Since data on whether the microbiome normalises or remains altered after resection of CRC are conflicting, we studied the colonic microbiota of patients after resection of CRC. We profiled the microbiota using 16S rRNA gene amplicon sequencing in colonic biopsies from patients after resection of CRC (n=63) in comparison with controls (n=52), subjects with newly diagnosed CRC (n=93) and polyps (n=28). The colonic microbiota after surgical resection remained significantly different from that of controls in 65% of patients. Based on abundance profiles, 6 co-abundance groups (CAGS) were identified, one of which, the Lachnospiraceae cluster, was more prevalent after CRC resection. A CRC-associated CAG dominated by known pathogens such as Fusobacterium and Streptococcus was significantly depleted after surgical resection. Genus-level profiling and beta-diversity confirmed two distinct groups of patients after resection of CRC: one with an abnormal microbiota similar to that of patients with newly diagnosed CRC and another similar to non-CRC controls. Consumption levels of several dietary ingredients and cardiovascular drugs co-varied with differences in microbiota composition suggesting lifestyle factors may modulate differential microbiome trajectories after surgical resection. The microbiome may be a biomarker for identifying a subset of patients with greater risk of development of a new CRC after removal of a primary CRC.