Dogs like Cliff are giving a whole new meaning to ‘pet scan’
In the ongoing battle to control in-hospital bacterial infections, Dutch researchers think they may have come up with a secret weapon: a dog named Cliff.
Turns out that, when properly trained, a dog’s highly honed and superior sense of smell can be effectively harnessed to sniff out early signs of a common but problematic infection known as Clostridium difficile, or C. difficile.
Exhibit A: Cliff, a 2-year old beagle who has already demonstrated a remarkable ability to diagnose infections simply by nosing around patients and their stool samples.
“C. difficile can cause an infection of the bowel, ranging from mild symptoms of diarrhea to severe illness,” explained study author Dr. Marije Bomers, an internist at the VU University Medical Centre, in Amsterdam. “The bacterium mostly affects older patients in a hospital or health care facility after the use of antibiotics, since antibiotics disturb the normal balance of bacteria present in our bowel.”
“Once a patient has a C. difficile bowel infection, the infection can spread to other patients on the same ward,” Bomers noted, stressing the importance of prompt identification followed by patient quarantine to prevent spread. “However, in reality it can take a couple of days before a C. difficile infection is identified, allowing the bacteria to spread and infect more patients.”
In the Dec. 13 online edition of the journal BMJ, Bomers’s team reported on its unconventional new approach.
“In this research project we’ve trained a beagle called Cliff to identify the smell of C. difficile and subsequently tested its skills,” she said. “It turned out that [spotting infections] was not that difficult for the dog.”
Since 2000, infection outbreaks — particularly in the United States and Canada — have grown in frequency and size, often prompting the wholesale closure of hospital wings, the authors noted. As a result, there has been an increased interest in the development of faster, more accurate and affordable infection-control measures.
The Dutch team spent two months using a reward-based training system to teach Cliff to pick up the unique odor of C. difficile, both in stool samples and among patients themselves.
After he learned to sit or lie down whenever the telltale scent was unearthed, the authors tested the dog’s talents on stool-sample identifications in a microbiology laboratory setting. The result: a nearly perfect diagnostic record.
Between 2010 and 2011, Cliff was repeatedly guided through hospital wards in two Dutch facilities that were caring for a total of 300 patients, 30 of whom were infected with C. difficile. The guides were not told which patients were infected, and Cliff made no direct contact with any patients — he simply sniffed the air surrounding their beds before rendering his verdict.
After 10 such “detection rounds,” Cliff was successful in identifying C. difficile patients 83 percent of the time.
“The bottom line is, it is very feasible to train a detection dog to identify a superbug like C. difficile,” Bomers concluded.
While pointing to ongoing research exploring the ability of dogs to sniff out different types of cancer, Bomers cautioned that their usefulness at sniffing out other infections and diseases remains an open question. But she suggested that dogs might ultimately help to reduce the onset of C. difficile by serving as routine “pet scans” that catch the first sign of an infection and halt an outbreak in its tracks.
“The idea holds great potential,” she said, “but more research has to be done first to see whether this concept actually works.”
Dr. Philip Tierno director of clinical microbiology and immunology at New York University Langone Medical Center in New York City, confirmed that dogs are already used for other types of diagnostic ventures, and that setting them on the hunt for C. difficile infections “makes eminent sense.”
“This organism has a characteristic odor, which can be smelled by any medical personnel that’s familiar with it,” he explained. “For a lack of a better word, I would describe it as a barnyard odor, much like horse manure. It’s very characteristic.”
“We currently use dogs to smell out bed bugs, which give off a smell when they cluster that can be detected by a dog but not by a human,” Tierno noted.
He added that he has noticed C. difficile scent in samples from patients with “overt medical manifestation of infection. But as our ability in terms of scent is nowhere near that of a dog, there’s no doubt in my mind that it makes sense to use an animal for this purpose.”