Though healthcare-associated transmission of C. difficile is a significant concern in public health, the numbers of healthcare-onset infections (CDI) are often comparable to those originating in the community. This equivalence brings forward the often-ignored interaction between these two settings. Aiming to gauge in-hospital transmission and the hospital’s contribution to community colonisation, this study introduced two crucial parameters, the intrinsic reproduction number (Ri) and the colonization amplification index (Ai). Ri quantifies in-hospital transmission, while Ai underscores the ratio of patients colonised at discharge against those at admission.
Considering the probable influence of exterior cases, the study also examined interventions focusing on asymptomatic carriers at admission to diminish the disease burden. A compartment-based model, furnished by UCSF Medical Center data, was employed to understand the C. difficile transmission dynamics among symptomatic and asymptomatic patients. Simulations identified a median Ri of 0.58, suggesting a limited and unsustainable in-hospital transmission due to Ri<1. Conversely, Ai was 1.9, implying a considerable amplification of colonization during hospital stay.
Factors such as discharge rates, antibiotic exposure, and case thresholds were found to influence the estimates. Targeting asymptomatic carriers could potentially diminish both Ri, Ai and consequently, CDI incidence. A combination of interventions yielded maximum reductions. The study finds that while in-hospital transmission of C. difficile is limited and perhaps buoyed by continuous case importation from the community, hospital stays significantly boost colonization, contributing to community transmission.
The results emphasize the urgent need to implement interventions that approach asymptomatic carriers, a group mostly overlooked presently, while also reassessing metrics beyond Ri for capturing hospitals’ contribution to the C. difficile problem. Future infection control strategies should address admission and potentially discharge colonisation dynamics to curtail transmission and lessen the overall C. difficile burden. The research followed all relevant ethical guidelines and approvals from relevant bodies. The work received financial support from the Centers for Disease Control and Prevention and NIH NIGMS.
Source: https://www.medrxiv.org/content/10.1101/2025.10.09.25337452v1