Dogs are now able to sniff out clostridium difficile with significant accuracy in samples of feces as well as the air around patients in the hospital, suggests a new study published in BMJ.

Clostridium difficile is an infective component that causes many hospital acquired infections. A detection dog can recognize clostridium difficile in stool, thus identifying sick patients.

Earlier studies established that dogs can detect certain cancers, which are verified by the current findings, implying promising potential for hospital ward reviews to prevent outbreaks of C. difficile.

For example, one study detailed how dogs were trained to detect cell-derived volatile organic compounds (VOCs) specific to prostate cancer in urine. They correctly identified 33 patients with biopsy-confirmed prostate cancer via their urine samples.

A separate study conducted by researchers from Schillerhoehe Hospital in Germany showed scent detecting dogs are able to identify VOCs unique to lung cancer in exhaled breath samples. This is a critical outcome because symptoms are few and early detection is quite difficult for this deadly disease.

C. difficile infection generally occurs in elderly patients who had a stint of antibiotics during a hospital stay, however, it can also begin in the community, such as in care homes for older adults. Symptoms can span from slight diarrhea to fatal inflammation of the bowel.

In order to prevent spread of C. difficile, early detection is crucial. However, current diagnostic tests can be costly and slow, delaying treatment for up to one week.

Diarrhea triggered by C. difficile has a distinct smell. Since dogs have such a keen sense of smell, this motivated a group of researchers from the Netherlands to explore whether a dog could be taught to identify C. difficile.

Without ever being trained for detection purposes before, a male beagle named Cliff, aged 2 years, was taught by a trainer how to detect C. difficile in stool samples as well as in patients with C. difficile infection. He was trained to recognize the presence of this particular scent by lying down or sitting.

The dog was trained for two months and then underwent a test to try his scent abilities. He smelled 50 C. difficile positive and 50 C. difficile negative feces samples. He correctly identified all 50 positive samples and 47 out of 50 negative samples.

This gave Cliff a score of 100 percent sensitivity and 94 percent specificity. Sensitivity calculates the proportion of positives correctly chosen and specificity calculates the proportion of negatives correctly chosen.

To test his abilities, Cliff was taken into two hospital wards to use his sense of smell with patients. He correctly identified 265 out of 270 negative controls (specificity 98 percent) and 25 out of 30 cases (sensitivity 83 percent).

The authors also note that the dog was quick and systematic, reviewing a whole hospital ward for the presence of patients with C. difficile infection in under 10 minutes.

The researchers identify some study limitations:

  • the unpredictability of using an animal as a diagnostic tool
  • the potential for transmission of infections via the dog

They suggest that some unanswered questions still remain, but their study shows that a detection dog can be taught to recognize C. difficile with a great degree of accuracy, in hospitalized patients and in stool samples.

The investigators conclude, “This could have great potential for C. difficile infection screening in healthcare facilities and thus contribute to C. difficile infection outbreak control and prevention.”

Written by Kelly Fitzgerald