Dr. Carolyn Alonso wraps herself in a yellow gown, dons a mask, and pumps a hand dispenser twice. Once her hands are dry, she puts on gloves and a mask, and then she goes in to see a 58-year-old patient called Karen.

Karen is from Hyde Park, and she's embarrassed by her symptoms, so she asked us not to use her full name. She had a bone marrow transplant last year. As she was recovering, she got severe diarrhea.

"I had to keep the commode next to my bed," Karen said. "I couldn't get to the bathroom. I couldn't never make it."

Karen had contracted something called Clostridium difficile – or "C. diff" for short. In most cases it causes bad diarrhea, but it can also lead to sepsis and death. Recently an article in the New England Journal of Medicine reported that C. diff cases have skyrocketed, killing more than 29,300 people a year and costing U.S. hospitals as much as $4.8 billion annually.

The White House took new steps last week to stop so-called superbugs — anti-biotic drug-resistant bacteria that attack about 2 million people a year. The administration issued a plan to commit more lab space and set new goals so fewer people get sick from these pathogens.

The C. diff infection complicated Karen’s case, extending her hospital stay, and causing her to lose pounds she couldn’t spare.

"Wish I could go home the same way I came in a year and a half ago," she said.

C. diff takes over after patients have been given antibiotics for some other infection. Those drugs wipe out the good bacteria in a patient’s colon. C. diff bacteria uses that window of opportunity — it comes into the colon and proliferates, making it tough for the good bacteria to return. Infected patients have to be isolated so the C. diff doesn’t spread to others.

There are treatments, but they don’t eliminate the bug entirely, so researchers like Alonso have focused on preventing people from getting the infection in the first place. She’s part of an international effort to test the first-ever vaccine on humans.

“Our hope is that by giving the vaccine we can wipe out C. diff like we’ve wiped out many other preventable infections in the past,” Alonso said.

The study being conducted at Beth Israel targets at-risk patients who are willing to take the vaccine and come in for check-up appointments for a year. Alonso says recruiting participants can be tough.

"They’re sometimes bed-bound, they’re many times in the ICU, it can be challenging to enroll those ill patients in clinical studies," she said. "So I think that’s the major limitation that we face."

Looking back, Robert Ethier says now that he would’ve happily participated in the trial for the smallest chance the vaccine worked. The 60-year-old is a local public health official in Bourne. He went into the hospital for a pancreas transplant in 2008. He got C. diff and, with drugs, fought it off.

“I started getting better and then I finally got rid of the C. diff," Ethier said. "But little did I know it would ever come back. But I guess if you talk to the doctor, once you get it, the chances that you get it again are there."

Someone who’s had C. diff has a 20 percent chance of getting it again. And someone who’s had it twice has a 50 percent chance of getting it a third time. A few weeks ago Ethier got sick with his second round of C. diff. Every time he ate, he got sick, and he could barely stay hydrated. He lost 13 pounds. But Ethier's upbeat since his symptoms are on the decline.

“My stuff is minor to some of the cases and stories I’ve heard about," he said. "I’ve been very lucky."

Alonso is straightforward about the fact that the C. diff vaccine might not work. But she says cases like Ethier’s make it important to try.

“They are living a horrible existence," Alonso said. "They feel isolated, worried about finding the closest bathroom if they go out, and wondering when’s this going to end.”

A successful vaccine couldn’t help people like Ethier who’ve already had C. diff, but Alonso says it might keep others from ever experiencing what he’s been through.