Changes in Bacteroides and the microbiota in patients with obstructed colorectal cancer: retrospective cohort study

Background The relationship between intestinal obstruction due to colorectal cancer (CRC) and the gut microbiota remains largely unknown. The aim of this study was to investigate the potential association between alterations in gut microbiota and CRC in the presence of intestinal obstruction. Methods Patients with CRC with or without obstruction were recruited and compared using 1:1 propensity score matching (PSM). Total DNA from tumours and adjacent normal tissues of 84 patients and 36 frozen tumour tissues was extracted and amplified. 16S RNA sequencing was used to uncover differences in microbiota composition between the two groups. Results A total of 313 patients with CRC were recruited. Survival analysis demonstrated that patients in the obstruction group had shorter overall survival time and disease-free survival (DFS) time than those in the non-obstruction group. Microbial richness and diversity in tumour tissues of patients with obstruction were significantly higher than those of patients with no obstruction. The alpha diversity indices and beta diversity exhibited were different between the two groups (P < 0.05). At the phylum and genus levels, Bacteroidetes were significantly enriched in the tumour tissues of patients with obstruction. Alpha diversity in tumour tissues was closely related to specific microbiota. These findings were replicated in the 16S rRNA analyses from frozen samples. There were more Bacteroidetes in CRC patients with obstruction. Conclusions Patients with obstructed CRC have worse prognosis and have differences in their microbiota. Higher levels of Bacteroides were observed in patients with obstructed CRC.