May 17, 2017

Which Bacteria Are Lurking in Your Dog's Nose?

Next-generation sequencing revealed differences in bacterial populations in the noses of healthy dogs and dogs with nasal disease.
By JoAnna Pendergrass, DVM
Using next-generation sequencing (NGS), a team of investigators identified differences in bacterial populations in the noses of healthy dogs and dogs with nasal disease.

Study results, published in PLoS ONE, “suggest a complex role of the nasal microbiome in the disease process,” the investigators wrote.
 
Dogs have a rich, complex microbial community. Microbiome composition has been studied in healthy dogs. However, it remains unclear whether the canine nasal microbiome plays a primary or secondary role in nasal disease development. To date, according to the investigators, the nasal microbiome of healthy dogs has not yet been compared with that of dogs with nasal disease.
 
NGS is a revolutionary DNA sequencing technology that has provided in-depth insights into bacteria–host interactions. Few veterinary studies, though, have used NGS to evaluate the canine nasal microbiome. The current study is the first to use NGS to analyze canine nasal microbiome composition in dogs with nasal disease.
 
Study Design
Investigators divided 47 pet dogs into 3 groups according to nose health: (1) healthy, (2) nasal neoplasia, and (3) chronic rhinitis. Two nasal swabs were collected from each dog. From each swab, genomic DNA was extracted and the bacterial 16S rRNA gene was sequenced; the 16s rRNA gene is found in all bacteria and is commonly used to analyze bacterial phylogeny and taxonomy.
 
Several analyses were conducted. For example, bacterial diversity was determined using indices such as the Shannon diversity index, which measures species abundance and evenness. Principal coordinate analysis (PCoA) was performed to visualize similarities and differences between clusters of microbial communities. Investigators also determined whether associations existed between bacterial taxa and nose health (healthy vs diseased).
 
Results
Healthy dogs were significantly younger than dogs with nasal neoplasia. Body weight was not significantly different among dogs in the 3 groups.
 
Healthy Dog Nasal Microbiome
PCoA indicated that microbial communities in healthy dogs were not clustered according to demographic factors, such as age, body weight, or cephalic index.
 
The Shannon diversity index was significantly higher for dogs aged 9 to 12 years than for younger dogs, and for small dogs (< 10 kg) compared with larger dogs. Interestingly, the nasal microbiome was no more similar in dogs living in the same household than those living separately.
 
Nasal Microbiome Comparisons
Investigators observed significant differences in the nasal microbiome between healthy dogs and those with nasal neoplasia, but not between dogs with chronic rhinitis and the other groups. Regarding species richness, the Shannon diversity index was markedly lower for the healthy dogs than the dogs with nasal disease.
 
Across all groups, Proteobacteria was the most abundant phylum and Moraxellaceae (within the Proteobacteria phylum) was the most abundant family; the relative abundance of this family was markedly higher in the healthy dogs than in the other dogs. The Pasteurellaceae family, also within the Proteobacteria phylum, was significantly more abundant in dogs with nasal neoplasia than in healthy dogs. Also, the Mycoplasmataceae family was notably abundant in several dogs with chronic rhinitis.
 
Conclusions and Discussion
Taken together, study results highlighted the microbial diversity of the canine nasal cavity. Importantly, NGS allowed for levels of bacterial detection not previously possible with culturing. Because it remains unknown whether changes in the canine nasal microbiome are primary or secondary to nasal disease, investigators proposed studying “the complex interactions between [the] nasal microbiome, host immune response, and canine nasal disease.”
 
 
Dr. JoAnna Pendergrass received her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.

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