Introduction
Faecal microbial markers are emerging as valuable non-invasive tools for colorectal cancer (CRC) screening in average-risk populations. However, their utility in Lynch Syndrome (LS) carriers—a high-risk hereditary condition characterized by unique genetic and physiological features—remains largely unexplored.
Aims & Methods
This study investigates whether LS carriers exhibit distinct faecal microbial signatures compared to average-risk individuals, aiming to assess the potential of microbial markers to inform LS-specific surveillance strategies.
Faecal samples were collected from LS carriers undergoing routine surveillance colonoscopy and from participants in the Catalonia CRC screening program prior to screening colonoscopy. Quantitative PCR (qPCR) was employed to quantify selected bacterial markers: F. prausnitzii (FPRA), its phylogroups I (PHGI) and II (PHGII), P. stomatis (PTST), B. fragilis (BCTF), B. thetaiotaomicron (BCTT), B46 (best BLAST match: S. variable), G. morbillorum (GMLL), B48 (best BLAST match: Ruminococcus, Roseburia, and Coprococcus), E. coli (ECO), and Eubacteria (EUB) as total bacterial load. Participants from both cohorts were categorized by colonoscopy findings into normal colonoscopy (NC), non-advanced lesions (NAL), and advanced lesions (AL, including advanced adenomas and CRC). Statistical comparisons included t-tests and multivariate analysis of variance (MANOVA) following isometric log-ratio (ILR) transformation.
Results
LS carriers demonstrated significantly distinct faecal bacterial profiles relative to average-risk individuals, independent of lesion presence. Across the full cohort, LS carriers showed increased abundances of PTST (p<0.001), BCTT (p<0.001), B46 (p<0.001), and ECO (p<0.001), along with reduced levels of PHGI (p=0.017) and B48 (p=0.030).
In individuals with NC, LS carriers exhibited higher abundances of PTST (p<0.001), BCTT (p=0.010), B46 (p=0.025), ECO (p=0.017), and PHGI (p=0.041). Among those with NAL, LS carriers again presented higher abundances of BCTT (p=0.015), B46 (p<0.001), FPRA (p=0.012), ECO (p=0.043), and PHGI (p=0.024). In AL cases, LS carriers displayed a marked reduction in the abundance of BCTF (p<0.001) and an increase in the abundance of BCTT (p=0.043).
MANOVA analysis revealed significant differences in overall bacterial panel composition between LS carriers and average-risk individuals at each lesion stage (NC: p<0.001; NAL: p<0.001; AL: p=0.009).
Conclusion
LS carriers harbour a consistently distinct faecal bacterial profile compared to average-risk individuals, with differential abundance patterns evident across all stages of colorectal lesion development. These results highlight the importance of identifying and validating LS-specific bacterial markers, rather than extrapolating from average-risk cohorts, to enhance surveillance and early detection strategies tailored to this high-risk population.
Disclosure
S. Taboada-López, M. Malagón, L. Oliver, M. Serra-Pagès and S. Ramió-Pujol are employees of GoodGut.