Changes of the intestinal microbiota, short chain fatty acids, and fecal pH in patients with colorectal cancer.

New molecular biology-based methods of bacterial identification are expected to help elucidate the relationship between colorectal cancer (CRC) and intestinal microbiota. Although there is increasing evidence revealing the potential role of microbiota in CRC, it remains unclear whether microbial dysbiosis is the cause or the result of CRC onset. We investigated the changes of intestinal environments in CRC or adenoma. We analyzed 13 groups of microbiota, 8 types of organic acids, and pH in feces obtained from the following 3 groups: individuals with CRC, adenoma, and non-adenoma. Ninety-three patients with CRC and 49 healthy individuals (22 with adenoma and 27 without adenoma) were enrolled. The counts of total bacteria (10.3 ± 0.7 vs. 10.8 ± 0.3 log10 cells/g of feces; p < 0.001), 5 groups of obligate anaerobe, and 2 groups of facultative anaerobes were significantly lower in the CRC group than in the healthy individuals. While the concentrations of short chain fatty acids (SCFAs) were significantly decreased in the CRC group, the pH was increased in the CRC group (7.4 ± 0.8 vs. 6.9 ± 0.6; p < 0.001). Comparison among the CRC, adenoma, and non-adenoma groups revealed that fecal SCFAs and pH in the adenoma group were intermediate to the CRC group and the non-adenoma group. Within the CRC group, no differences in microbiota or organic acids were observed among Dukes stages. CRC patients showed significant differences in the intestinal environment, including alterations of microbiota, decreased SCFAs, and elevated pH. These changes are not a result of CRC progression but are involved in CRC onset.