Fecal <i>Cloacibacillus porcorum</i> Improves Non-Invasive Diagnosis of Colorectal Adenoma in the Hong Kong Population

We previously developed a four-marker panel for the diagnosis of colorectal cancer (CRC) and adenoma. This study aimed to identify novel bacterial markers to improve adenoma detection using metagenomics and qPCR. Candidate markers were identified from metagenomic data (<i>n</i> = 492) using ANCOM-BC2 and Spearman's rank correlation analysis and were subsequently validated in an independent cohort (<i>n</i> = 426). Diagnostic performance was assessed both individually and in combination with our previously identified markers and FIT. Metagenomic analysis identified 21 candidate markers that increased along the normal-adenoma-carcinoma axis. Two top candidates, <i>Cloacibacillus porcorum</i> (Cp) and <i>Intestinimonas butyriciproducens</i>, were validated via qPCR and showed significant correlations with metagenomic abundances (both <i>p</i> < 0.0001). ROC analysis demonstrated that Cp levels significantly distinguished CRC and adenoma from controls, whereas <i>I</i>. <i>butyriciproducens</i> distinguished only CRC. The prevalence of Cp was significantly higher in adenoma and CRC than in controls (all <i>p</i> < 0.05). Multivariate analysis confirmed that Cp was independently associated with CRC and adenoma diagnoses. Adding Cp to the four-marker panel improved diagnostic sensitivity from 44.8% to 58.7% for adenoma and from 85.7% to 88.6% for CRC (specificity = 85%). When further combined with FIT, Cp improved sensitivity from 47.6% to 64.3% for adenoma and from 95.2% to 96.2% for CRC (specificity = 84.6%). <i>C</i>. <i>porcorum</i> is a novel bacterial marker that may aid in the non-invasive diagnosis of colorectal adenoma.