Old and new models for studying host-microbe interactions in health and disease: C. difficile as an example

There has been an explosion of interest in studying the indigenous microbiota, which plays an important role in human health and disease. Traditionally, the study of microbes in relationship to human health involved consideration of individual microbial species that caused classical infectious diseases. With the interest in the human microbiome, an appreciation of the influence that complex communities of microbes can have on their environment has developed. When considering either individual pathogenic microbes or a symbiotic microbial community, researchers have employed a variety of model systems with which they can study the host-microbe interaction. With the use of studies of infections with the toxin-producing bacterium Clostridium difficile as a model for both a pathogen and beneficial bacterial communities as an example, this review will summarize and compare various model systems that can be used to gain insight into the host-microbe interaction.