2368. Molecular Epidemiology of Clostridioides difficile Infections in Pediatric Oncology and Transplant Patients

BACKGROUND: The incidence of Clostridioides difficile infection (CDI) has been rising among children, both in the community and hospital setting. The genomic variability and molecular epidemiology of CDI in children, especially with cancer are poorly understood. We aim to evaluate the molecular epidemiology and relatedness of C. difficile isolates among inpatient and outpatient pediatric oncology and stem cell transplant patients (POTP) using whole-genome sequencing (WGS). METHODS: This was a retrospective cohort study of CDI in POTP in 2016. CDI cases were identified by electronic medical record search for positive C. difficile toxin PCR tests. Retrieved residual stool specimens were cultured anaerobically using pre-reduced CCMB-TAL broth (Anaerobe Systems, Inc.), toxin-producing C. difficile isolates were determined using a cell culture cytotoxicity assay with neutralization (TechLab, Inc.), and WGS was performed, followed by core genome MLST (cgMLST). Variability of the isolates was summarized by strain type (ST), and a minimum spanning tree was constructed, defining clusters of genomically related isolates as those with < 7 alleles difference. Plausible epidemiologic links among the closely related strains such as receiving care on the same inpatient unit on the same day or on the same unit but on different days within 8 weeks before CDI were evaluated to identify potential transmission events. RESULTS: Among 141 CDI episodes in 89 patients; 103 stool samples were cultured, and 101 (98%) isolates were sequenced identifying 23 different strain types in 81 (80%) isolates. 34 (38%) patients had multiple episodes of CDI. 16 clusters of related isolates were identified (figure), 10 (62%) of which involved only multiple specimens from the same patient. For the 6 clusters involving multiple patients, epidemiologic investigation revealed only 2 (33%) potential transmission events. CONCLUSION: WGS identified a highly diverse group of C. difficile isolates among POTP with CDI. Although WGS identified clusters of closely related isolates in multiple patients, epidemiologic investigation of shared inpatient exposures identified potential transmission in only two clusters. C. difficile transmission was uncommon. [Image: see text] DISCLOSURES: Randall Hayden, MD, Abbott Molecular: Advisory Board; Quidel: Advisory Board; Roche Diagnostics: Advisory Board.