Distinct microbiota in patients diagnosed with colorectal cancer compared to healthy individuals

Objective: The gastrointestinal tract consists of a complex microenvironment with an abundance of microorganisms, and a diverse microbiome composition is evident along the gastrointestinal tract with a favorable growth environment for bacteria. Dysbiosis to this environment have been associated with colorectal cancer (CRC) as well as other diseases, with studies identifying a higher number of bacteria, such as the Enterobacteriaceae family: Clostridium spp., Fusobacterium spp., and Streptococcus bovis. We hypothesize that patients with CRC have a distinct microbiota with a greater abundance of atypical Campylobacter spp. and Helicobacter spp. compared to control patients. Patients and Methods: Sixty biopsies were collected from forty randomly selected patients in Kaunas, Lithuania. The patients were allocated into groups: patients with CRC and control patients without intestinal cancer or cancer risk factors. Twenty biopsies were collected from each collection site: The tumor and the adjacent intestinal tissue in CRC patients, and a randomly selected intestinal tissue site in non-cancer patients. A microbiome analysis was performed using 16S rDNA and 18S rDNA. Results: Distinct bacterial microbiota was found to be significantly different in the collected biopsies between CRC patients and control patients with p=.001. There was a clear overrepresentation of Campylobacter spp. with C. rectus being the most prominent in CRC patients. Moreover, Fusobacterium spp. was found in each group, with increased abundance of F. nucleatum and F. necrophorium in cancer tissue. There was no significant abundance of the Helicobacter spp. found. Conclusions: This pilot study illustrates a significant difference in the gut microbiota in patients with CRC compared to non-cancer patients. The microenvironmental composition in CRC tissue samples were dominated by Campylobacter spp. and Fusobacterium spp. suggesting that these species either solely or in co-aggregation may cause or promote CRC.