Each year in the United States, billions of dollars are spent combating almost half a million infections (CDIs) and trying to reduce the ∼29,000 patient deaths in which has an attributed role. In Europe, disease prevalence varies by country and level of surveillance, though yearly costs are estimated at €3 billion. One factor contributing to the significant health care burden of is the relatively high frequency of recurrent CDIs. Recurrent CDI, i.e., a second episode of symptomatic CDI occurring within 8 weeks of successful initial CDI treatment, occurs in ∼25% of patients, with 35 to 65% of these patients experiencing multiple episodes of recurrent disease. Using microbial communities to treat recurrent CDI, either as whole fecal transplants or as defined consortia of bacterial isolates, has shown great success (in the case of fecal transplants) or potential promise (in the case of defined consortia of isolates). This review will briefly summarize the epidemiology and physiology of infection, describe our current understanding of how fecal microbiota transplants treat recurrent CDI, and outline potential ways that knowledge can be used to rationally design and test alternative microbe-based therapeutics.
