Fecal host biomarkers predicting severity of Clostridioides difficile infection

Background Clostridioides difficile is a major cause of healthcare-associated diarrhea. Severity ranges from mild to life-threatening, but this variability remains poorly understood. Microbiological diagnosis of C. difficile infection (CDI) is straightforward, but offers little insight into the patient's prognosis, nor into pathophysiological determinants of clinical trajectory. The aim of this study was to discover host-derived, CDI-specific, fecal biomarkers involved in disease severity. Methods Subjects without and with diarrhea were recruited. CDI was established by commercial, diagnostic real-time PCR assay of tcdB. CDI severity was based on IDSA/SHEA criteria. We developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) approach to identify host-derived protein biomarkers from stool and applied it to diagnostic samples for cohort-wise comparison (CDI-negative vs. non-severe CDI vs. severe CDI). Selected biomarkers were orthogonally confirmed and subsequently verified in a CDI mouse model. Results We identified a protein signature from stool, consisting of alpha-2-macroglobulin (A2M), matrix metalloproteinase-7 (MMP7) and alpha-1-antitrypsin (A1AT), that not only discriminates CDI-positive samples from non-CDI ones, but is potentially associated with disease severity. In the mouse model, this signature with the murine homologs of the corresponding proteins was also identified. Conclusions A2M, MMP7 and A1AT serve as biomarkers in patients with CDI and define novel components of the host response that may determine disease severity.