If the idea of fecal transplants seems momentarily disquieting, consider that they achieve a 90 percent cure rate for the devastating intestinal infection known as C. diff when antibiotics fail to clear it. Fecal transplants are also being studied as treatment for colitis, Crohn’s disease, and other inflammatory gastrointestinal disorders, and research into their value for urinary tract infections and even Parkinson’s disease is underway. By transferring stool in sterile conditions from a donor to the intestines of someone who is ailing, fecal transplants are designed to introduce a healthy mix of gut bacteria into the body and restore bacterial balance. What’s that good for?