Short- and long-term dynamics of gut microbiota, highlighting Fusobacterium nucleatum, Parvimonas micra, and Peptostreptococcus stomatis after colorectal cancer resection: prospective cohort study.
Colorectal cancer resection induces acute postoperative disruption of gut microbiota followed by recovery of overall diversity, but colorectal cancer-associated bacteria (F. nucleatum, P. micra, and P. stomatis) remained persistently reduced after surgery, highlighting their dependence on the tumour microenvironment.
Key Findings
Results
Alpha diversity of gut microbiota decreased acutely at 1 week after colorectal cancer resection and recovered by 1 month post-surgery.
83 faecal samples were collected from 28 patients with colorectal cancer and 16 healthy 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
The recovery of alpha diversity by 1 month suggests relatively rapid restoration of species richness and evenness
Results
Beta diversity metrics indicated that gut microbial community composition did not fully return to its preoperative state by 6 months after surgery.
Unweighted unique fraction metric (UniFrac) suggested recovery of community membership by 6 months
Bray-Curtis dissimilarity and weighted UniFrac remained altered at 6 months
These persistent changes indicate ongoing community reorganization beyond 6 months post-surgery
The findings indicate 'stabilization in a state that does not fully recapitulate the preoperative microbiota'
Results
At the class level, Negativicutes and Clostridia decreased at 1 week post-surgery and gradually recovered, while Bacilli showed a transient increase.
Negativicutes and Clostridia both declined in relative abundance at 1 week after colorectal cancer resection
These classes gradually recovered over the subsequent follow-up period
Bacilli demonstrated a transient increase post-surgery before returning toward baseline levels
These class-level changes reflect the broader acute disruption of gut microbial community structure following surgery
Results
Fusobacterium nucleatum, Parvimonas micra, and Peptostreptococcus stomatis declined significantly after colorectal cancer resection and remained suppressed at 6 months.
All three colorectal cancer-associated bacteria were quantified using quantitative polymerase chain reaction (qPCR)
The decline in these bacteria was observed after curative surgical resection
Suppression persisted through the 6-month follow-up timepoint
The authors interpret this persistent reduction as highlighting 'their dependence on the tumour microenvironment'
This pattern contrasts with the broader gut microbiota, which showed substantial recovery by 6 months
Results
Patients who developed colorectal cancer recurrence had higher preoperative levels of Parvimonas micra and Peptostreptococcus stomatis compared to those who did not recur.
Differences in P. micra and P. stomatis levels between recurrence and non-recurrence groups were observed only at the preoperative timepoint
Differences in these bacteria between groups were not observed after surgery
F. nucleatum levels were not specifically noted to differ between recurrence groups
The sample size was relatively small (28 colorectal cancer patients), which may limit statistical power for recurrence analyses
The authors suggest monitoring these bacteria may offer 'a non-invasive means to assess microbiota recovery and potential recurrence risk'
Discussion
The persistent reduction of colorectal cancer-associated bacteria after resection suggests these bacteria are dependent on the tumour microenvironment for their enrichment in the gut.
F. nucleatum, P. micra, and P. stomatis are established colorectal cancer-associated bacteria
Their sustained suppression after tumour removal implies the tumour itself, or its local microenvironment, facilitates their colonization or proliferation
This finding supports the concept that these bacteria are not simply opportunistic colonizers of a dysbiotic gut but are specifically enriched by tumour-related factors
The authors highlight this as evidence of 'their dependence on the tumour microenvironment'
Conclusions
Faecal monitoring of colorectal cancer-associated bacteria may serve as a non-invasive approach to assess microbiota recovery and recurrence risk after surgery.
The study was designed as a prospective cohort study with serial faecal sample collection
Faecal qPCR quantification of F. nucleatum, P. micra, and P. stomatis was feasible across all timepoints
Preoperative levels of P. micra and P. stomatis were associated with subsequent recurrence
The authors propose this approach as a 'non-invasive means to assess microbiota recovery and potential recurrence risk'
What This Means
This research suggests that removing a colorectal cancer tumor has both immediate and lasting effects on the bacteria living in the gut. In the first week after surgery, the overall variety of gut bacteria dropped sharply, but by one month after surgery, diversity had largely bounced back. However, even at six months post-surgery, the overall composition of the gut microbial community had not fully returned to what it looked like before the operation, suggesting the surgery causes a lasting reorganization of gut bacteria populations.
More strikingly, three specific bacteria that are known to be elevated in colorectal cancer patients — Fusobacterium nucleatum, Parvimonas micra, and Peptostreptococcus stomatis — dropped significantly after tumor removal and stayed low throughout the entire six-month follow-up period. This pattern was different from the broader gut microbiome, which recovered substantially. This finding suggests these bacteria thrive specifically because of the tumor itself, not just because of a generally unhealthy gut environment. Additionally, patients who later experienced cancer recurrence tended to have higher levels of P. micra and P. stomatis before their surgery, hinting that these bacterial levels might carry prognostic information.
This research suggests that measuring these specific bacteria in stool samples could potentially offer doctors a simple, non-invasive way to track how a patient's gut microbiome is recovering after colorectal cancer surgery and possibly to identify patients at higher risk of cancer recurrence. The study was relatively small (28 cancer patients and 16 healthy controls), so larger studies will be needed to confirm these findings and determine whether stool-based bacterial monitoring could be practically useful in clinical care.
Mukoyama T, Yamashita K, Saito M, Fujita M, Omura S, Emoto T, et al.. (2026). Short- and long-term dynamics of gut microbiota, highlighting Fusobacterium nucleatum, Parvimonas micra, and Peptostreptococcus stomatis after colorectal cancer resection: prospective cohort study.. BJS open. https://doi.org/10.1093/bjsopen/zrag037