Micro-organisms play roles in colorectal cancer, is it true?

Abstract

BACKGROUND: Normal gut bacterial floras play a direct or indirect role in the initiation and progression of tumour by inducing chronic inflammation and producing toxins and metabolites. However, data on the types of bacteria that are significant in the sigmoid colon and rectal tumour are still lacking. This study determined the types of bacteria that are associated with the risk of developing sigmoid colon and rectal cancer.

METHODS: This case control study involved patients with bowel symptoms and had been subjected to elective colonoscopy procedure from December 2013 to September 2014. Standard bowel preparation was carried out two days prior to colonoscopy either at home or in ward. Biopsy samples were sent to microbiology laboratory for cultivation. The mean of bacterial colonies in the mucosa of sigmoid colon tumour and rectal tumour were compared with the mucosa of normal sigmoid colon and rectum, respectively.

RESULTS: For normal colonoscopy results, 66 biopsies were taken from bowel mucosa (33 at sigmoid colon and 33 at rectum). Eight patients had sigmoid colon tumour and 25 patients had rectal tumour. The results showed that Clostridium subterminale, Finegoldia magna, Enterococcus avium, Eggerthella lenta, Parvimonas micra, Clostridium bifermentans, beta-hemolytic streptococcus, Streptococcus mutans and Morganella morganii were only present in sigmoid colon tumour and were significantly associated with sigmoid colon cancer (p = 0.041). More than 15 types of bacteria were isolated in the rectal tumour compared to the normal rectal mucosa, however, only Proteus mirabilis (p = 0.040) and Morganella morganii (p = 0.046) were significant in promoting rectal cancer.

CONCLUSION: Clostridium subterminale, Finegoldia magna, Enterococcus avium, Eggerthella lenta, Parvimonas micra, Clostridium bifermentans, beta-hemolytic streptococcus, Streptococcus mutans and Morganella morganii were associated with the risk of developing sigmoid colon cancer while Proteus mirabilis and Morganella morganii were associated with rectal cancer.