A Review of Mixed Strain Colonization and Infection.

Given that is not part of the normal human microbiota, if multiple strains are to accumulate in the colon implies successive exposure events and/or persistent colonization must occur. Evidence of infection (CDI) with more than one strain was first described in 1983. Despite the availability of increasingly discriminatory bacterial fingerprinting methods, the described rate of dual strain recovery in patients with CDI has remained stable at ∼5-10%. More data are needed to determine when dual strain infection may be harmful. Notably, one strain may block the establishment of and infection by another. In humans, patients colonized by non-toxigenic strain are at a lower risk of developing CDI. Further studies to elucidate the interaction between co-infecting or colonizing and infecting strains may help identify potential exploitable mechanisms to prevent CDI.