WASHINGTON - A superbug named C-diff is on the rise, a germ that so ravages some people's intestines that repeated tries of the strongest, most expensive antibiotic can't conquer their disabling diarrhea.

Now a few doctors are trying a last-ditch treatment: Using good bacteria to fight off the bad by transplanting stool from a healthy person into the sick person's colon.

Yes, there's a yuck factor. But reports of several dozen cases this fall suggest that with no more inconvenience than a colonoscopy, people who have suffered C-diff for months, or longer, can rapidly improve.

"This is the ultimate probiotic," says Dr. Lawrence Brandt, of New York's Montefiore Medical Center, who has performed 17 of the procedures.

It is almost like an organ transplant minus the anti-rejection drugs, says Dr. Alexander Khoruts, of the University of Minnesota. He examined the gut bacteria in a woman left emaciated after eight months of C-diff. Not only did the diarrhea disappear after a fecal transplant, but that normal bacteria mirroring her husband's - the donor - took root in her recovering intestine.