Short- and long-term dynamics of gut microbiota, highlighting Fusobacterium nucleatum, Parvimonas micra, and Peptostreptococcus stomatis after colorectal cancer resection: prospective cohort study

Abstract Background Colorectal cancer is associated with gut microbiota alterations, including enrichment of colorectal cancer-associated bacteria such as Fusobacterium nucleatum, Parvimonas micra, and Peptostreptococcus stomatis. However, the impact of curative resection on their postoperative dynamics remains unclear. Methods Faecal samples were collected from patients with colorectal cancer and controls. Samples were collected before surgery and at 1 week, 1 month, and 6 months after surgery. Microbial diversity was evaluated using 16S ribosomal RNA sequencing, and F. nucleatum, P. micra, and P. stomatis were quantified by quantitative polymerase chain reaction. Results A total of 83 faecal samples were collected from 28 patients with colorectal cancer and 16 healthy controls. Alpha diversity decreased at 1 week and recovered by 1 month. Unweighted unique fraction metric suggested recovery of community membership by 6 months, whereas Bray–Curtis and weighted unique fraction metric remained altered, indicating persistent community reorganization. At the class level, Negativicutes and Clostridia decreased at 1 week and gradually recovered, whereas Bacilli showed a transient increase. In contrast, F. nucleatum, P. micra, and P. stomatis declined significantly after surgery and remained suppressed at 6 months. Patients who developed recurrence had higher preoperative P. micra and P. stomatis levels, though differences were not observed after surgery. Conclusion Colorectal cancer resection induces an acute postoperative disruption of the gut microbiota, followed by recovery of overall diversity and major taxonomic features, but stabilization in a state that does not fully recapitulate the preoperative microbiota. Colorectal cancer-associated bacteria (F. nucleatum, P. micra, and P. stomatis) remained persistently reduced after surgery, highlighting their dependence on the tumour microenvironment. Monitoring these bacteria in faecal samples may offer a non-invasive means to assess microbiota recovery and potential recurrence risk.