There is growing interest in the role of gut microbiome in colorectal cancer (CRC), ranging from screening to disease recurrence. Our study aims to identify microbial markers characteristic of CRC and to examine if changes in bacteriome persist after surgery. Forty-nine fecal samples from 25 non-cancer (NC) individuals and 12 CRC patients, before and 6-months after surgery, were collected for analysis by bacterial 16S rRNA gene sequencing. Bacterial richness and diversity were reduced, while pro-carcinogenic bacteria such as Bacteroides fragilis and Odoribacter splanchnicus were increased in CRC patients compared to NC group. These differences were no longer observed after surgery. Comparison between pre-op and post-op CRC showed increased abundance of probiotic bacteria after surgery. Concomitantly, bacteria associated with CRC progression were observed to have increased after surgery, implying persistent dysbiosis. In addition, functional pathway predictions based on the bacterial 16S rRNA gene data showed that various pathways were differentially enriched in CRC compared to NC. Microbiome signatures characteristic of CRC comprise altered bacterial composition. Elements of these dysbiotic signatures persists even after surgery, suggesting possible field-change in remnant non-diseased colon. Future studies should involve a larger sample size with microbiome data collected at multiple time points after surgery to examine if these dysbiotic patterns truly persist and also correlate with disease outcomes.

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ObjectiveThere is growing interest in the role of gut microbiome in colorectal cancer (CRC), ranging from screening to disease recurrence. Our study aims to identify microbial markers characteristic of CRC and to examine if changes in bacteriome persist after surgery. Design49 fecal samples from non-cancer (NC) individuals and CRC patients, before and after surgery, were collected for analysis by bacterial 16S rRNA gene sequencing. ResultsBacterial richness and diversity were reduced in the CRC patients compared to NC individuals. Pro-carcinogenic bacteria such as Bacteroides fragilis and Odoribacter splanchnicus were increased in pre-op CRC compared to NC group. These differences were no longer observed after surgery. Comparison between post- and pre-op CRC showed increased abundance of probiotic bacteria after surgery. Concomitantly, bacteria associated with CRC progression were observed to have increased after surgery, implying persistent dysbiosis. ConclusionMicrobiome signatures characteristic of CRC likely comprise a set of significant alteration in specific bacterial strains. Elements of these dysbiotic signatures persists even after surgery, suggesting possible field-change in remnant non-diseased colon. Future studies should seek to examine if these signatures are also associated with pre-malignant colonic polyps and, explore if these profiles can be used to guide CRC screening and surveillance.

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