Fecal Metabolomics for the Diagnosis of <em>Clostridioides difficile</em> Infection

Clostridioides difficile infection (CDI) is the leading cause of nosocomial diarrhea. Current diagnostic tools have difficulty distinguishing between colonization and active infection. This study evaluated the utility of fecal metabolomics in diagnosing CDI in hospitalized patients with acute diarrhea. We conducted a prospective observational study involving hospitalized adults with new-onset diarrhea during admission. Participants were strati-fied into groups based on clinical and microbiological findings: controls, C. difficile col-onized and C. difficile infected. Fecal samples were analyzed using UPLC-MS/MS and GC-MS to quantify selected short-chain fatty acids, amino acids, and bile acids. Multi-variate and univariate statistical analyses included PLS-DA, sPLSDA, and tests with FDR correction. Infected patients exhibited significantly higher concentrations of SCFAs and notable alterations in bile acid profiles. Key discriminative metabolites included isova-lerate, propionate, isobutyrate and alpha-aminobutyric acid. ROC curve analyses showed strong diagnostic performance for these markers, with AUC values exceeding 0.85. Fecal metabolomic profiling could effectively differentiate between colonization and infection in CDI among hospitalized patients with diarrhea. These results highlight the potential of metabolomic signatures to enhance the diagnostic precision for CDI.