In patients with unexplained polyps in the colon, those who have a specific DNA damage pattern linked to colibactin are more likely to carry bacteria in their gut that produce colibactin, compared to those without this DNA pattern.

In patients with unexplained polyps and specific DNA damage patterns, detecting a bacterial gene in stool along with a unique tumor mutation pattern identifies colibactin exposure in 87% of cases, compared to 25% when only one method is used.

Certain strains of E. coli that produce a toxin called colibactin are linked to a specific pattern of DNA damage found in colorectal tumors. This DNA damage pattern is more commonly found in tumors from people diagnosed with colorectal cancer before age 55 compared to those diagnosed at age 59 or older.

Colorectal cancers diagnosed before age 40 are more likely to show specific DNA damage patterns linked to colibactin-producing bacteria than cancers diagnosed after age 70, suggesting that exposure to these bacteria earlier in life may be associated with faster development of tumors in the lower colon and rectum.

The presence of certain bacterial genes in stool samples does not reliably indicate how much DNA damage is present in colon tumors, meaning the amount of these bacteria alone cannot be used to predict tumor damage levels in individuals.

Researchers found that DNA damage patterns linked to a specific bacterial toxin were present in 39% of colorectal tumors from individuals with APC gene variants, compared to 11% in individuals without these tumors. This suggests a statistical relationship between the bacterial toxin and the type of DNA damage observed in these cancers.