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

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. 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. 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. These findings suggest associations between loading of F. nucleatum or/and B. fragilis with the advanced stages of CRC. •B. fragilis infection is higher in CRC vs. polyps, with a fivefold increased load.•Positive association with CRC progression in stages II and III.•Elevated F. nucleatum infection rates in CRC tissues.•Higher F. nucleatum load in stage III CRC.•Implications for therapeutic strategies in CRC.