Detecting Clostridioides (Clostridium) difficile using canine teams: What does the nose know?

Dogs' ability to detect an inflammatory immune response in cattle via olfaction

Introduction

Canine olfaction is a potential means for detection of respiratory disease in beef cattle. In a prior study, two dogs were trained to discriminate between nasal swabs from healthy cattle and cattle that developed Bovine Respiratory Disease. Dogs had some ability to identify samples from BRD-affected cattle, but results were ambiguous. The purpose of this study was to evaluate more dogs using better-controlled training and testing procedures.

Methods

Nasal and saliva swabs were collected from 96 cattle before and after administering a vaccine to induce an inflammatory immune response. Samples were stored at -80°C for up to 11 months before use, and samples from animals with an elevated body temperature at baseline were omitted. An automated olfactometer apparatus was constructed to improve blinding procedures and reduce opportunities for odor contamination. Four dogs were trained to distinguish between swabs from healthy and sickness-model cattle, including the two dogs from the previous study ("Runnels" and "Cheaps") and two inexperienced dogs ("Molokai" and "Amy"). During a seven-month training period, dogs were exposed to samples from 28 animals. Dogs were tested on 59 sets of unfamiliar samples.

Results

Performance varied among dogs (χ2 = 10.48, p = 0.02). Molokai's performance was above chance (0.73 ± 0.06, p = 0.0006), while Amy (0.44 ± 0.06, p = 0.43), Cheaps (0.53 ± 0.07, p = 0.79), and Runnels (0.56 ± 0.06, p = 0.43) did not respond correctly at a rate different from chance. Accuracy did not differ between nasal swabs (0.63 ± 0.08) and saliva swabs (0.53 ± 0.08, χ2 = 0.81, p = 0.37).

Discussion

The results of this study indicate that canine olfaction may be an effective means of detecting illness in beef cattle. However, individual dogs' aptitude for this detection task varies.

In search of COVID-19: The ability of biodetection canines to detect COVID-19 odours from clinical samples

BACKGROUND

COVID-19 continues to be a public health concern and the demand for fast and reliable screening tests remains. SARS-CoV-2 infection in humans generates a specific volatile organic compound signature; this 'volatilome' could be used to deploy highly trained canine scent detection teams if they could reliably detect odours from infected individuals.

METHODS

Two dogs were trained over 19 weeks to discriminate between the odours produced by breath, sweat, and gargle specimens collected from SARS-CoV-2 infected and uninfected individuals. Third party validation was conducted in a randomized double-blinded controlled manner using fresh odours obtained from different patients within 10 days of their first positive SARS-CoV-2 molecular result.

RESULTS

Cumulatively, the dogs completed 299 training sessions on odours from 108 unique participants. Validation was conducted over 2 days with 120 new odours. Twenty-four were odours collected from SARS-CoV-2 positive individuals (8 gargle, 8 sweat, and 8 breath); 21 were from SARS-CoV-2 negative individuals (5 gargle, 8 sweat, and 8 breath) and the remaining 75 were odours that the dogs could have associated with the target odour during training. The dogs were able to identify odours from positive specimens with an overall sensitivity of 100% and a specificity of 87.5%. Considering a community prevalence of 10%, the combined negative predictive value of the dogs was 100% and the positive predictive value was 47.1%.

CONCLUSIONS

Multiple dogs can be trained to accurately detect SARS-CoV-2 positive individuals. Future research is required to determine how and when canine scent detection teams should be deployed.

Thiol Metabolism and Volatile Metabolome of Clostridioides difficile

Clostridioides difficile (previously Clostridium difficile) causes life-threatening gut infections. The central metabolism of the bacterium is strongly influencing toxin production and consequently the infection progress. In this context, the composition and potential origin of the volatile metabolome was investigated, showing a large number of sulfur-containing volatile metabolites. Gas chromatography/mass spectrometry (GC/MS)-based headspace analyses of growing C. difficile 630Δerm cultures identified 105 mainly sulfur-containing compounds responsible of the typical C. difficile odor. Major components were identified to be 2-methyl-1-propanol, 2-methyl-1-propanethiol, 2-methyl-1-butanethiol, 4-methyl-1-pentanethiol, and as well as their disulfides. Structurally identified were 64 sulfur containing volatiles. In order to determine their biosynthetic origin, the concentrations of the sulfur-containing amino acids methionine and cysteine were varied in the growth medium. The changes observed in the volatile metabolome profile indicated that cysteine plays an essential role in the formation of the sulfur-containing volatiles. We propose that disulfides are derived from cysteine via formation of cystathionine analogs, which lead to corresponding thiols. These thiols may then be oxidized to disulfides. Moreover, methionine may contribute to the formation of short-chain disulfides through integration of methanethiol into the disulfide biosynthesis. In summary, the causative agents of the typical C. difficile odor were identified and first hypotheses for their biosynthesis were proposed.

The State of Animal-Assisted Interventions: Addressing the Contemporary Issues that will Shape the Future

As the worldwide popularity of animal-assisted interventions (AAIs) increases, the fieldis quickly approaching a paradigm shift, adjusting its image to incorporate more evidence-basedresearch and aligning its purpose for advancing a new future. Contemporary critical issues thatconfront the field today include, but are not limited, to research, animal welfare, practice guidelines,and public policy. This article will provide an overview of the history of AAI and the majormilestones that the field has undergone. The current state of AAI research will be scrutinized, andthe areas that warrant further study will be recommended. Special attention will be given to thecurrent state of animal welfare in AAI, the research that has been done in the area, and practiceguidelines that safeguard animal wellbeing. This article will then discuss how evidence-basedresearch and animal welfare guidelines inform the development of comprehensive professionalstandards and influence changes in public policy regarding AAI. The authors' perceptions for thefield's future trajectory will be presented, which will include solutions to move the field in thedirection that best advances the human-animal bond in research, practice, and public perception.