Among patients with CDI who clinically recovered following treatment with metronidazole or vancomycin, oral administration of spores of NTCD-M3 was well tolerated and appeared to be safe. Nontoxigenic C. difficile strain M3 colonized the gastrointestinal tract and significantly reduced CDI recurrence.It's a fascinating study and I recommend reading it. In addition to contemplating this as a potential future treatment for recurrent CDI, it's intriguing to wonder if patients could have their GI tracts colonized by nontoxigenic C. diff prophylactically before receiving antibiotics associated with CDI.
The notion of exploiting microbial ecology is appealing for many reasons, including that it doesn't require developing intrinsically new pharmacologic compounds and that it may have no significant side effects. At the same time, its important to remember previous trials employing bacterial interference, such as the deliberate colonization of newborn children with "low virulence" Staph. aureus, so that old missteps aren't repeated.