A simple and novel fecal biomarker for colorectal cancer: Ratio of Fusobacterium nucleatum to probiotics populations, based on their antagonistic effect

Abstract

BACKGROUND: Gut microbial dysbiosis contributes to the development of colorectal cancer (CRC). We evaluated the utility of fecal bacterial biomarker candidates identified by our 16S rDNA sequencing analysis for CRC diagnosis. METHODS: We measured the relative abundance of Fusobacterium nucleatum (Fn), Faecalibacterium prausnitzii (Fp), Bifidobacterium (Bb), and Lactobacillus (Lb) by quantitative PCR in fecal samples from 2 cohorts of 903 individuals. We evaluated and validated the diagnostic performance of these microbial ratios and investigated the antagonistic effect of Fn against 3 different indicator stains. RESULTS: The microbial ratio of Fn to Bb (Fn/Bb) had a superior sensitivity of 84.6% and specificity of 92.3% in detecting CRC (area under the curve, AUC= 0.911). The combination of Fn/Bb and Fn/Fp improved the diagnostic value (AUC= 0.943). Moreover, the combination of Fn/Bb and Fn/Fp offered 60.0% specificity and 90.0% sensitivity in detecting stage I of CRC (AUC= 0.804). In particular, Fn was negatively correlated with Fp in the CRC group. The performance for CRC diagnosis was confirmed in the validation cohort II. The culture supernatant from Fn exhibited strong bactericidal activity against probiotics Fp and Bb strains. CONCLUSIONS: This study found that Fn could play a role in microbiota dysbiosis via the secreted antagonistic substances against probiotics. Moreover, the ratio of Fn to the important probiotics Fp and Bb was identified as a valuable biomarker for screening early CRC.