Significant changes in the intestinal environment after surgery in patients with colorectal cancer.

Background: There have been very few detailed reports of the intestinal environment after surgical treatment for colorectal cancer (CRC). We analysed faecal microbiota, organic acids and pH to investigate the influence of colorectal surgery on the intestinal environment.

Methods: Faecal samples from 81 CRC patients were collected before the start of pre-operative preparation the day before surgery, as well as 7 days or more after surgery. Thirteen groups of intestinal microbiota, eight types of organic acids, and pH were measured using 16S rRNA-targeted reverse transcription-quantitative PCR, high-performance liquid chromatography and a pH meter, respectively.

Results: Total bacterial counts (10.3 ± 0.6 vs. 9.4 ± 1.2 log10 cells/g; p < 0.001) and the numbers of 6 groups of obligate anaerobes were significantly decreased after surgery. In contrast, the populations of Enterobacteriaceae, Enterococcus, Staphylococcus and Pseudomonas were significantly increased. Post-operatively, the concentration of total organic acids was lower (77.9 ± 40.1 vs. 50.1 ± 37.0 μmol/g; p < 0.001) than the pre-operative concentration, and a significant reduction in short-chain fatty acids (SCFAs) was observed.

Conclusion: Significant changes in the intestinal environment, including marked decreases in obligate anaerobes, increases in pathogenic bacteria, and reductions in SCFAs, were detected after surgery for CRC.