Dog trained to sniff out deadly C. difficile superbug

Dogs have proven themselves to be effective ‘physicians’ in the medical world – many trained canines are capable of detecting everything from life-threatening cancers, to drops in blood sugar and oncoming seizures.

Now, man’s best friend has proven himself to be a valuable medical aid yet again, this time by being able to effectively sniff out patients suffering from Clostridium difficile – a dangerous and potentially deadly, ‘superbug.’

This breakthrough revolves around the efforts of a 2-year-old male beagle named Cliff. Researchers from VU University Medical Center in Amsterdam have successfully trained Cliff to detect the smell of C. difficile in both stool samples and the air surrounding patients in hospitals.  By simply sitting or lying down, Cliff can easily indicate the presence of the superbug – with up to 83 percent accuracy.

Cliff’s achievements could potentially lead to better screening techniques in hospital wards, areas most at risk for breakouts of C. difficile.

“The whole problem with C. diff is it’s transmissible,” the study’s lead author Dr. Marije Bomers, a consultant internist and infectious disease specialist at VU University Medical Center, told “If one patient has it in the ward and you don’t isolate the patient, it’s not just one patient – it’s two, it’s three, and then half your ward has C. diff.  In order to try and prevent transmission in your hospital, it’s important to recognize C. diff patients as early as possible.”

C. difficile is considered to be one of the most serious health care-associated infections (HAI) in the past couple of years, often affecting elderly hospital patients who have been recently treated with antibiotics.  Hailed as a deadly superbug, the rise of the bacteria has been attributed to the overuse of antibiotics in hospitals, because it is resistant to most antibiotic medication.

For the majority of healthy patients, C. difficile often harmlessly resides in the gut, but becomes a serious medical issue when the normal gut flora is destroyed by antibiotics, allowing for the spread and overabundance of the deadly bacteria.  Those suffering from C. difficile often have watery diarrhea multiple times a day, as well as abdominal cramping, fever and nausea – making it difficult to differentiate between normal diarrhea and the much more serious condition.

However, one significant distinguishing factor is the distinct odor associated with C. difficile.

According to Bomers, the inspiration for the project came when she realized it wasn’t that difficult to make out the C. difficile smell for herself.

“I was discussing a patient who had diarrhea and wondering if it could be caused by C. diff, and one of the nurses said it smells like it could be caused by C. diff,” Bomers said. “So, that made us think if humans can distinguish the smell, and detection dogs have a far superior sense of smell – maybe they can be trained to identify the sense of smell of C. diff.”

Through various professional contacts, Bomers was introduced to Hotsche Luik, a psychologist-turned-professional animal trainer.  Very experienced in training police search dogs, Luik decided to train her own dog Cliff for the project.

“It’s a known system of conditioning,” Luik told  “The value of the smell – we made it important and fun for him. First, we used lots of smells where I could almost smell it, and that was easy for him to find.  Then it became more fun and a challenge to find it.”

Bomers and Luik went from using petri dishes containing C. difficile in its most pure form to hiding the smell in cubes and in the woods.  After two months of training, Cliff’s abilities were tested on 50 stool samples testing positive for C. difficile and 50 samples testing negative.

He was able to correctly identify all 50 positive samples and 47 out of the 50 negative samples – equating to 100 percent sensitivity and 94 percent specificity.

Just six months after starting the conditioning process, they deemed Cliff ready to visit the hospital to assess his detective skills on real patients.  Once a patient was determined to have contracted C. difficile, Bomers would ask if they could bring in Cliff to do testing.

Of 30 patients with the bacteria, Cliff was able to identify 25 of them – equating to 83 percent sensitivity.  Conversely, he was able to identify 265 out 270 negative controls – equating to 98 percent specificity.

According to Bomers, training more dogs like Cliff could be a cheap and effective way for hospitals to routinely screen for C. difficile.  Early detection of the superbug can lead to earlier treatment for patients, increasing the odds of a person’s survival.  Otherwise, they may not realize they have contracted the bacteria until it’s too late.

While the incidence of C. difficile is quite low in the Netherlands, the superbug is at historical rates in the U.S., affecting 14,000 people each year, according to the CDC.  While Bomers said she hopes to further her research in countries like American where superbugs are becoming significant problems.

“At the moment, I can’t take it any further here,” Bomers said. “I’d have to go elsewhere and see where it goes…. But if there are hospitals or areas with high C. diff incidence, this could really help lower that.”

The study was published online in the British Medical Journal (BMJ).