Clostridioides difficile infection cases in University Hospital Centre Zagreb

Background: Intra-hospital distribution of Clostridioides difficile strains in hospitals is not continuously analyzed. Methods: We investigated the intra-hospital distribution of C. difficile strains by whole genome sequencing (WGS) isolates collected in 2022 at the University Hospital Centre (UHC) Zagreb. Demographic and clinical data were prospectively analyzed from electronic medical records. All samples were subjected to WGS analysis. Genetic clusters were formed from isolates with =6 allelic differences by core genome MLST. Results: In total, 103 patients with the first episode of CDI in 2022 at UHC Zagreb were included, based on the screening stool antigen test for GDH (RidaQuick CD GDH; R-Biopharm AG, Germany), confirmed by Eazyplex C. difficile assay (Eazyplex CD assay; AmplexDiagnostics GmbH, Germany) specific for A, B and binary toxins. We identified six clusters containing 2-59 isolates with 15 singletons and 30 instances of possible intra-hospital transmission, mostly in the COVID-19 ward. Conclusions: WGS analysis proved useful in identifying clusters of isolates connecting various patient wards with possible transmission routes in the hospital setting. It could be used to support local and national surveillance of CDI infections and their transmission pathways.