Dogs engage in scent science to sniff out staph bacteria

oranyone who has taken their beloved dog for a walk knows how an athletic excursion can quickly turn into a contemplative stroll between every tree trunk and fire hydrant in the neighborhood. A dog’s intense need to check their urine mail is fueled by their powerful sense of smell. Researchers have found ways to harness this superpower to detect volatile organic compounds (VOCs), the byproducts of metabolism produced by organisms from the most powerful animals to the tiniest microbes.¹ This ability makes dogs ideal companions for medical scent detection research.

In a recent study published in Frontiers in Allergyscientists hired a special group of furry recruits whose job it was to drown stubborn Staphylococcus aureus infections.² “The study was born out of the poor diagnostic ability to detect bacterial biofilms, particularly with joint infections,” said Meghan Ramos, medical director of the Penn Vet Working Dog Center at the University of Pennsylvania School of Veterinary Medicine and co-author of the study. . The research team put their canine colleagues to work by training them to detect the distinctive VOC biomarker signature of S. aureus biofilms in vitro, with the hope of finding a new way to detect infections that accumulate in orthopedic implants after surgery.

Eight dogs of different breeds participated in the study, four of which were recruited from the Penn Vet Working Dog Center and four from their community science program, which involves dogs practicing nose work with dogs through scent-detection sports. . Dogs were hired for their personality traits and ability to focus on tasks rather than specific breed characteristics.

Qualifications for working dogs included high drive, high energy and a constant need for mental stimulation. The qualifications for a medical sniffer dog are even more rigorous, requiring critical thinking, razor-sharp task focus and mental resilience. If the VOC signature were a concoction, the dogs would be expected to identify and distinguish each individual ingredient. “We want them to critically evaluate the wind profile we’re asking them to look for. They should be motivated to work to get a treat or toy without being discouraged,” said Ramos.

In this study, dogs were first taught to identify S. aureus VOCs from scent-rich cotton balls are absorbed by cell culture biofilms and alert researchers using a trained response, such as sitting or lying down. “We use that cotton ball to show the dogs and say, this is what you’re smelling, this is the scent we want you to smell. It starts simply: you smell this, you get a cookie, you smell this, you get a toy. This is the simple process where they realize that this is now what they are looking for,” Ramos described. The researchers presented the dogs with the mixture of scents and taught them which specific one was correct.

After being trained on these VOC odor cues, the canine super sniffers were tested on tear duct fluid from rabbits with and without joint infections. The researchers first taught the dogs what healthy tear duct fluid smells like, then presented them with samples from infected rabbits. The dogs excelled at identifying the unique bacterial scent in rabbit biological samples with a high degree of sensitivity and specificity, even in the early stages of infection. The researchers already tested this approach on tear duct fluid from a small number of people with confirmed conjunctival infection. Preliminary results were promising, but more testing is needed.

“We’re really in an exciting place. Dogs are changing the way we perceive illness. We’re also changing people’s perception of what a biomarker is to include these volatile organic compounds,” said Cynthia Otto, director of the Penn Vet Working Dog Center, who co-authored this study. “When we started this , no one was thinking about volatile organic compounds, but now we have expanded the possibilities to make a diagnosis and develop technology to help save lives, whether they are human or animal.”

The broader aim of this work is to utilize the excellent noses of dogs to inform the development of a bedside or laboratory test to screen for and diagnose bacterial biofilms, providing a future route for non-invasive testing, early detection and treatment of intended. “Dogs are educating our material, our robots, our industry, so that we can scan large amounts of disease, not just bacterial biofilms. We’re using dogs as a tool to advance our knowledge and understanding,” Ramos said.

Drupad Trivedi, a biomedical researcher and lecturer in analytical and measurement science at the University of Manchester, who was not involved in the study, believes the work addresses key hurdles in training and translating canine medical scent detection. “Training generalization is often a struggle when the sample is complex, as in this case. By training dogs on biofilms in vitro and then testing on samples from rabbits and humans, the authors have shown that odorous VOCs in the case of S. aureus the infection is not masked or altered by the matrix,” Trivedi said.

For now, the chemicals that make up S. aureus The signature of the VOC is still a mystery. “The exact scent profile now only exists in our dogs’ noses and brains. I would like them to tell me what they are,” said Ramos.