Prevalence of -positive in Japanese patients with or without colorectal cancer.

Background: Recent studies show that some strains possessing a gene cluster named the island might have a causative role in the development of human colorectal cancer (CRC). In several reports from Europe, they are found more prevalently in colon tissue specimens derived from CRC patients compared to those from controls. In this study we sought to clarify the difference in prevalence between CRC patients and non-CRC controls in the Japanese population, by using non-invasive sample collection technique during colonoscopy.

Methods: Colonic lavage samples were collected during diagnostic colonoscopy, and bacterial DNA within each sample was extracted. Fecal DNA samples were then examined for island genes using conventional qualitative PCR and real-time quantitative PCR. In some patients biopsy samples were also collected in the same session of colonoscopy, and the correlation between the status of the colonic lavage sample and the biopsy sample of the same patients was evaluated.

Results: Twelve out of thirteen patients (92%) showed the same status by colonic lavage sample and biopsy sample, suggesting the usefulness of colonic lavage samples as a surrogate for biopsy samples. A total of 98 colonic lavage samples were collected, which included 35 from CRC patients, 37 from adenoma patients, and 26 from controls. The -positive bacterial DNA was detected in 43, 51, and 46% of colonic lavage samples from CRC, adenoma, and control patients, respectively, and there was no significant difference among diseases. Real-time quantitative PCR showed no significant difference in the relative concentrations of -positive bacterial DNA among diseases. Age, gender, location of CRC, CRC staging, or - gene status was not associated with prevalence.

Conclusions: Although the method of collecting fecal DNA from colonic lavage samples was safe and technically feasible, factors other than -positive bacteria appear to play more important roles in CRC development in this cohort.