# Clostridioides difficile infection study models and prospectives for probing the microbe-host interface

## TL;DR

This paper reviews current models for studying Clostridioides difficile infection and highlights the need for better systems to understand how the infection interacts with the host.

## Contribution

The paper provides a comprehensive review of in vivo and in vitro models for CDI and identifies gaps in modeling the host-pathogen interface.

## Key findings

- In vivo models are essential for understanding host responses but face limitations in accessibility and translatability.
- In vitro models offer better control and accessibility but struggle to model the host-pathogen interface.
- Alternative co-culture platforms are being developed to address these limitations.

## Abstract

Clostridioides difficile infection (CDI) is an urgent public health threat with a high rate of recurrence and limited treatment options. In vivo models have been indispensable in understanding CDI pathophysiology and establishing treatment protocols and continue to be essential in pre-clinal testing. More importantly, in vivo models offer the opportunity to probe the complex systemic host response to the microbe, which is impossible to recapitulate in vitro. Nonetheless, constraints related to the availability of animal models, cost, ethical considerations, and regulatory control limit their accessibility for basic research. Furthermore, physiological and habitual divergences between animal models and humans often result in poor translatability to human patients. In addition to being more accessible, in vitro CDI models offer more control over experimental parameters and allow dynamic analysis of early infection. In vitro fermentation offers models for probing microbe-microbe and microbe-microbiome interactions, while continuous multi-stage platforms allow opportunities to study C. difficile pathophysiology and treatment in context with human-derived microbiota. However, these platforms are not suitable for probing the host-pathogen interface, leaving the challenge of modeling early CDI unanswered. As a result, alternative in vitro co-culture platforms are being developed. This review evaluates the strengths and weaknesses of each approach, as well as future directions for C. difficile research.