Tina Leeb is an expert in microbiology. For the past three years, the experienced microbiologist has conducted research... read more
With their keen sense of smell, scent detection dogs are hunting down the bacterium Clostridioides difficile in hospitals. But how accurate are four-legged infection prevention and diagnostics? Recent studies investigate how well canines perform.
Sit. Stay. Sniff. These might be among the commands for sniffer dogs who are searching for the Clostridioides difficile bacterium. In Canada, within 18 months of the Vancouver Coastal Health C. Diff. Canine Scent Detection Programme1, sniffer dogs inspected 659 locations and alerted their trainers 391 times to the presence of C. diff. – for example, in waiting areas, on equipment carts and in lavatories, even on the inside of a toilet paper dispenser.
Wherever the sniffer dogs detected the bacterium, a robot disinfected the surfaces using ultraviolet light that removes 99.9 per cent of C. diff. spores2. It is among the award-winning infection prevention measures at Vancouver Coastal Health, which also include voluntary and mandatory surveillance programmes.
The bacterium Clostridioides difficile (former Clostridium difficile), the pathogen that most often causes antibiotic-associated diarrhoea, has genetically specialised in hospital survival. According to a recent study by Nature Genetics, a strain that forms resistant spores is spreading among in-patient settings. Find the article here.
Along with routine inspections, canine scent detection has also been tested in urgent situations. Infection control researchers from Vrije Universiteit University Medical Centre in Amsterdam evaluated how effectively a sniffer dog identified patients with C. diff. infections during a hospital outbreak3. The beagle performed with a sensitivity (true positive) of 86 per cent and specificity (true negative) of 97 per cent. The study’s authors, including an animal behaviour expert from the Scent Detection Academy in Voorst, Netherlands, stated that sniffer dogs “could provide early and rapid identification of Clostridioides difficile infections”.
But how accurate are canine noses, really? In a study at Toronto’s Michael Garron Hospital, two sniffer dogs served as a “point-of-care” diagnostic tool for detecting toxin gene-positive C. diff. in the stool of patients4. Infection control experts calculated scent detection sensitivity, specificity, and how coherent skills are between animals. The dogs demonstrated only a moderate interrater reliability (κ = 0.53) – whether they identify the same samples as infected, for example. Expressing concern that this would not be sufficient for hospital settings, senior author of the paper Dr Jeff Powis wrote, “Dogs will never reliably achieve the accuracy of current highly sensitive molecular diagnostic tests for C. difficile.”
Another hurdle remains regarding hygiene. With the possible exception of therapy dogs, animals are not allowed in most healthcare facilities. Although using sniffer dogs may help to identify where reservoirs of bacteria are hiding, scent detection is just one infection-prevention strategy. Systematic hand hygiene and surface disinfection are simple, verifiable and reliable methods.