Original Article

Presence and copy number variations of H. pylori, pks⁺ bacteria, E. faecalis, and B. bifidum in colorectal cancer: an integrated study using FFPE tissue samples

Abstract

Background and Objectives: Colorectal cancer (CRC) is a leading malignancy with multifactorial etiology, including genetic, environmental, and microbial factors. Bacteria such as Helicobacter pylori, pks⁺ bacteria, Enterococcus faecalis, and Bifidobacterium bifidum have been linked to CRC, though their roles remain controversial. Some may promote inflammation and genotoxicity, while others may confer protective effects. This study assessed the presence and relative abundance of these bacteria in colorectal FFPE tissue samples.
Materials and Methods: This case-control study included three groups of FFPE tissue samples: tumor tissues from CRC patients (Tumor, n=50), normal tissues adjacent to tumors (Adjacent, n=50), and normal tissues from non-CRC individuals (Normal, n=30). Sections were prepared with a microtome, and bacterial gene copy numbers were quantified using species-specific primers and quantitative real-time PCR, normalized to human GAPDH. Associations with age, sex, and neoplastic type were analyzed (p < 0.05).
Results: B. bifidum was significantly higher in Adjacent tissues compared to Tumor and Normal (p < 0.0001). H. pylori detection increased progressively from Normal to Adjacent to Tumor tissues (p = 0.002). pks⁺ bacteria were detected only in individuals ≥60 years (p = 0.014). E. faecalis load was higher in Tumor tissues of females and older adults, though overall presence did not differ significantly among groups.
Conclusion: Enrichment of B. bifidum and increased H. pylori detection near tumors suggest the tumor microenvironment favors bacterial persistence. Age- and sex-related patterns in pks⁺ and E. faecalis highlight host influences on microbial distribution in CRC, supporting further mechanistic studies.

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IssueVol 18 No 1 (2026) QRcode
SectionOriginal Article(s)
DOI https://doi.org/10.18502/ijm.v18i1.20907
Keywords
Colorectal neoplasms Tissues Polyketide synthases Helicobacter pylori Enterococcus faecalis Bifidobacterium bifidum
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How to Cite
1.
Korani F, Rezvani NA, Sadeghifard N, Sadeghi Kalani B, Pakzad R, Asadollahi P. Presence and copy number variations of H. pylori, pks⁺ bacteria, E. faecalis, and B. bifidum in colorectal cancer: an integrated study using FFPE tissue samples. Iran J Microbiol. 2026;18(1):55-66.