The association between specific bacteria and colorectal cancer (CRC) has been proposed. Only a few studies have, however, investigated this relationship directly in colorectal tissue with conflicting results. So, we aimed to quantitative Streptococcus gallolyticus, Fusobacterium spp, Enterococcus faecalis and enterotoxigenic Bacteroides fragilis (ETBF) in formalin-fixed and paraffin-embedded (FFPE) colorectal tissue samples of Iranian CRC patients and healthy controls. | Khodaverdi et al. BMC Cancer 2021 21 1353 https s12885-021-09110-x RESEARCH Open Access High frequency of enterotoxigenic Bacteroides fragilis and Enterococcus faecalis in the paraffin-embedded tissues of Iranian colorectal cancer patients Nasibeh Khodaverdi1 Habib Zeighami1 Ahmad Jalilvand2 Fakhri Haghi1 and Negar Hesami3 Abstract Background The association between specific bacteria and colorectal cancer CRC has been proposed. Only a few studies have however investigated this relationship directly in colorectal tissue with conflicting results. So we aimed to quantitate Streptococcus gallolyticus Fusobacterium spp Enterococcus faecalis and enterotoxigenic Bacteroides fragilis ETBF in formalin-fixed and paraffin-embedded FFPE colorectal tissue samples of Iranian CRC patients and healthy controls. Methods A total of 80 FFPE colorectal tissue samples of CRC patients n 40 and healthy controls n 40 were investigated for the presence and copy number of above bacterial species using quantitative PCR. Relative quantifica- tion was determined using ΔΔCT method and expressed as relative fold difference compared to reference gene. Results Relative abundance and copy number of E. faecalis and ETBF were significantly higher in CRC samples com- pared to control group. E. faecalis was more prevalent than ETBF in tumor samples. Frequency of ETBF and E. faecalis in late stages III IV of cancer was significantly higher than early stages I II . We did not detect a significant difference in abundance of S. gallolyticus and Fusobacterium spp between two groups. Conclusion Our study revealed the higher concentration of E. faecalis and ETBF in FFPE samples of CRC patients than controls. However additional investigations on fecal and fresh colorectal cancer tissue samples are required to substantiate this correlation. Keywords Bacteroides fragilis Colorectal cancer Enterococcus faecalis Fusobacterium spp Streptococcus gallolyticus Background including genetic .
