Dog Sniffs Out Deadly C. diff Infection

Salynn Boyles

December 14, 2012

A 2-year-old beagle named Cliff may hold the key to preventing an infection that kills thousands of Americans each year.

Researchers in the Netherlands taught Cliff to sniff out the intestinal bacteria Clostridium difficile(C. difficile or C. diff) in stool samples from infected patients and even from the patients themselves.

C diff is commonly spread in hospitals and long-term care centers, causing diarrhea that can be mild to life-threatening. It is responsible for as many as 14,000 deaths in the U.S. each year, the CDC says.

The hope is that other dogs can be trained to identify the infection far faster than it is found through current tests, preventing potentially deadly outbreaks in these settings.

“This study proves the concept, but we have to confirm that this approach will be useful in the real-world setting,” says researcher Marije K. Bomers, MD, of the VU University Medical Centre in Amsterdam, Netherlands.

Dogs Can Smell Better

Hospitalized older adults who have recently had a course of antibiotics are most at risk for C. diff infections.

Early detection can prevent the spread in hospitals and other care facilities, but current tests can take anywhere from two days to up to a week to confirm infection, Bomers says.

She says the idea for the study came from the observation that the diarrhea of patients with C. diff infections has a particular smell that she and her colleagues could sometimes detect.

It occurred to them that if humans could smell the infection some of the time, then dogs, with their superior sense of smell, should be able to smell it all the time.

To test the theory, they enlisted psychologist and dog trainer Hotsche Luik, who was also Cliff’s owner.

Over two months, the beagle was taught to identify the C. diff toxin in smaller and smaller quantities and in different samples, including human stool.

During one test, he correctly identified 50 of 50 C. diff positive stool samples and 47 of 50 negative samples.

In a separate test, he was taken to two hospital wards to examine his ability to sniff out the infection in patients.

He correctly identified C. diff in 25 of 30 infected patients. He also identified no infection in 265 of 270 non-infected patients.

He completed this task in one of the wards in less than 10 minutes.

New Type of ‘Pet Scan’

The researchers write that highly trained dogs like Cliff may one day patrol hospital wards to seek out C. diff infection.

“I love dogs. I think they are amazing,” says infection disease specialist Bruce Hirsch, MD, of North Shore University Hospital in Manhasset, N.Y. “But I’m not sure I see this being deployed in an efficient way in a large hospital setting where there are many distractions.”

Despite his skepticism, Hirsch says the research is definitely worth pursuing even though confirmation of the infection has already been shortened from a few days to a few hours in many hospitals, including his.

“One big question for me is, ‘What else can a dog’s amazing sensory apparatus be utilized to detect?'" he says. “There are already studies suggesting that they can smell some cancers. There is no telling what else they may be trained to sniff out.”


Bomers, M.K. BMJ, 2012.

Marije K. Bomers, MD, department of internal medicine, VU University Medical Center, Amsterdam, Netherlands.

Bruce Hirsch, MD, North Shore University Hospital, Manhasset, N.Y.

News release, BMJ, Dec. 13, 2013.

CDC: "Clostridium difficile Infection."