Association between Bacteroides fragilis and Fusobacterium nucleatum infection and colorectal cancer in Vietnamese patients

Background: Colorectal cancer (CRC) is a significant global health concern, and understanding the role of specific bacterial infections in its development and progression is of increasing interest. This cross-sectional study investigated the associations between Bacteroides fragilis (B. fragilis) and Fusobacterium nucleatum (F. nucleatum) infections and Vietnamese CRC patients. Methods: 192 patients with either polyps or CRC at varying stages were recruited from May 2017 to December 2020. Real-time PCR assessed infection rates and bacterial loads in CRC tissues. Results: B. fragilis infection was notably higher in CRC tissues (51.6 %) than polyps (9.4 %), with a fivefold higher relative load. Positive associations were found in stages II and III, indicating a fivefold increase in CRC progression risk. F. nucleatum infection rates were significantly higher in CRC tissues (55.2 %) than in polyps (10.5 %). In stage II, the infection rate exceeded that in adjacent tissues. The relative load of F. nucleatum was higher in stage III than in stages I and II. Positive F. nucleatum patients had a 3.2 times higher risk of CRC progression. Conclusion: These findings suggest associations between loading of F. nucleatum or/and B. fragilis with the advanced stages of CRC.