To quantify Fusobacterium spp., Enterococcus faecalis (E.faecalis), Enterotoxigenic Bacteroides fragilis (ETBF), and Enteropathogenic Escherichia coli in colorectal cancer (CRC) patients and their possible association with CRC clinicopathogical features, we collected the resected tumors and adjacent normal tissues (N) from 97 CRC patients. 48 age- and sex-matched healthy controls (HC) were also recruited. Real-time PCR was used for bacterial quantification. The median abundance ofFusobacterium spp.(p < 0.001, vs. N; p < 0.01,vs. HC), E.faecalis (p < 0.05, vs. N; p < 0.01, vs. HC) and ETBF (p < 0.001, vs. N; p < 0.05,vs. HC) in tumor tissues was significantly higher than that detected in normal tissue and HC. E.faecalis was detected in 95.88% of tumors and 93.81% of adjacent tissues. Fusobacterium spp. was detected in 72.16% of tumors and 67.01% of adjacent tissues. The combined E.faecalis and Fusobacterium spp. were detected in 70.10% of tumors and 36.08% of adjacent normal tissues. All four bacteria were detected in 33.72% and 22.09% of paired tumor and adjacent normal tissues, respectively. E.faecalis and Fusobacterium spp. are enriched in both tumor and adjacent tissue of CRC patients when compared to HC, suggesting that it is possible to be previously undetected changes in the pathohistologically normal colon tissue in the proximity of the tumor.
Keywords: colorectal cancer; enterococcus faecalis; enteropathogenic escherichia coli; enterotoxigenic bacteroidesfragilis; fusobacterium spp..