Microbial communities associated with humans or other animals tend to resist invasion by exotic species. But when ‘colonization resistance’ is lost, owing to antibiotic use, immunosuppression or other causes, the result can be difficult-to-control infections by invasive species or ‘blooms’ of indigenous opportunistic pathogens. The subsequent disease promotes further disruption of the gut microbiome, which in turn perpetuates the pathology. Thus, the disease might be both prevented and treated by manipulating the composition of the microbial community. A recent paper by Lawley et al.1 in PLoS Pathogens describes a useful experimental mouse model of colitis associated with Clostridium difficile, a pathogen that causes debilitating and sometimes fatal disease in humans. Using this model, the authors characterized healthy and diseased murine intestinal microbiota and showed that administration of a set of bacterial species representative of those in healthy animals succeeded in curing this recalcitrant infection.
