These days, antibiotics are no silver bullet. In fact, if you get them in the hospital, you may end up with an additional infection. Like the bug Clostridium difficile, or C. diff—which infects more than 300,000 Americans a year and kills some 14,000. C. diff flourishes in the post-antibiotic, microbe-free landscape of your gut. But there is a way to stop it—a fecal transplant. That cocktail of microbes from a healthy person's gut can rein in a C. diff outbreak. The question is not: Eewww? It’s: What are the transplant's active ingredients?

Well, one of them appears to be a bacterium called Clostridium scindens. Because in past studies, people and mice that harbored C. scindens were protected against a full-blown C. diff infection. So researchers dosed mice with the good guy, C. scindens, after a bout of antibiotics. And the treatment did indeed ward off C. diff, compared to a cocktail of other microbes, or nothing at all.

C. scindens makes a living by breaking down bile, the researchers say, and it's those secondary products that seem to inhibit C. diff. The findings are in the journal Nature. [Charlie G. Buffie et al: Precision microbiome reconstitution restores bile acid mediated resistance to Clostridium difficile]

This work could lead to more targeted probiotic treatments. But study author Eric Pamer of Memorial Sloan Kettering Cancer Center says it's worth remembering that when it comes to microbes, the sum is often greater than its parts. "In some ways I would say this is far more complex than an orchestra, in that there are many more interdependencies, and many of which we just don't understand yet, but that are starting to be illuminated by ongoing work." Now, at least, we know one of the featured performers.

—Christopher Intagliata

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]