Investigating in-hospital transmission of Clostridioides difficile from asymptomatic patients

Background: Clostridioides difficile is a bacillus that can colonize the intestinal tract. C. difficile infection (CDI) is a common, health care-associated disease often coinciding with antibiotic use, with presentation ranging from diarrhea to toxic megacolon and death. However, individuals can carry the pathogen without exhibiting symptoms of disease. C. difficile carriers may serve as an important reservoir for in-hospital transmission of C. difficile. The objective of this study was to assess the role asymptomatic C. difficile carriers may play in pathogen transmission. Methods: In this retrospective cohort study, rectal swabs collected to test for antimicrobial-resistant organisms either upon admission or during the hospital stay were used to test for asymptomatic C. difficile carriage using molecular testing, with positive samples cultured and subsequently sequenced. Sampling occurred across three tertiary care hospitals with predominantly multi-bedded rooms. A whole-genome single-nucleotide variant phylogenetic tree was then constructed and closely related samples from patients that had spatial and temporal in-hospital overlap were identified as putative transmission events. Results: Approximately 11% of the 1,467 patients tested were carriers of C. difficile. Seventy-four of the carriers were culture-positive, of which 43 had a suitable sequence for typing. Of the sequenced samples, 40% were identified as belonging to a potential transmission event. Six different potential transmission groups were identified, with the largest putative transmission group spanning two hospitals and 6 months. Conclusions: Our results suggest that asymptomatic transmission in hospital settings may be much more common than previously thought, with asymptomatic individuals colonized with C. difficile providing a sizable source of transmission of the pathogen.