Variations in facial conformation are associated with differences in nasal microbiota in healthy dogs

Abstract

Background: Extrinsic and intrinsic factors have been shown to influence nasal microbiota (NM) in humans. Very few studies investigated the association between nasal microbiota and factors such as facial/body conformation, age, and environment in dogs. The objectives are to investigate variations in NM in healthy dogs with different facial and body conformations. A total of 46 dogs of different age, living environment and from 3 different breed groups were recruited: 22 meso-/dolichocephalic medium to large breed dogs, 12 brachycephalic dogs and 12 terrier breeds. The nasal bacterial microbiota was assessed through sequencing of 16S rRNA gene (V1-V3 regions) amplicons.

Results: We showed major differences in the NM composition together with increased richness and α-diversity in brachycephalic dogs, compared to meso-/dolichocephalic medium to large dogs and dogs from terrier breeds.

Conclusion: Healthy brachycephalic breeds and their unique facial conformation is associated with a distinct NM profile. Description of the NM in healthy dogs serves as a foundation for future researches assessing the changes associated with disease and the modulation of NM communities as a potential treatment.

Keywords: Breed; Dogs; Facial conformation; Microbiota; Nasal cavity.

Fig. 1

Composition of nasal microbiota at phylum and family level in healthy dogs from 3 different breed groups

Fig. 2

Richness, evenness and α-diversity in healthy dogs from 3 different breed groups. Group DL = mesocephalic or dolichocephalic dogs of medium to large breeds. Group B = brachycephalic dogs of small breeds. Group T = mesocephalic or dolichocephalic terrier dogs of small breeds. *p < 0.05

Fig. 3

Non-metric multidimensional scaling (NMDS) ordination of nasal microbiota communities using Bray-Curtis in healthy dogs from 3 different breed groups. Significant clustering was observed between breed groups. (green, group DL; blue, group B; red, group T). Samples are represented by dots and the lines connecting dots are vectors defining the centromere of the group. Group DL = mesocephalic or dolichocephalic dogs of medium to large breeds. Group B = brachycephalic dogs of small breeds. Group T = mesocephalic or dolichocephalic terrier dogs of small breeds. Stress value = 0.1255474

Fig. 4

Total bacterial flora in healthy dogs from 3 different breed groups. Group DL = mesocephalic or dolichocephalic dogs of medium to large breeds. Group T = mesocephalic or dolichocephalic terrier dogs of small breeds. Group B = brachycephalic dogs of small breeds

Fig. 5

Linear discriminant analysis (LDA) effect size (LEfSe) at species level of Illumina sequencing datasets based on 16S rRNA gene sequences. Nine differentially abundant bacterial species were detected (p = 0.05, LDA score > 3.0) at species level. Of these, 8 bacterial groups were significantly over-represented in brachycephalic dogs (blue) and one bacterial group was over-represented in dogs of terrier breeds (yellow)

Fig. 6

Distribution of all detected OTUs between the 3 breed groups. Venn diagrams demonstrating the number of detected operational taxonomic units (OTUs) unique to each breed group and shared between one or more breed groups. The relative abundance of these OTUs within the total bacterial population is also indicated in brackets just below the number of shared/unique OTUs. Group DL = mesocephalic or dolichocephalic dogs of medium to large breeds. Group B = brachycephalic dogs of small breeds. Group T = mesocephalic or dolichocephalic terrier dogs of small breeds

Fig. 7

Sample collection. A sterile swab (Copan®, FLOQSwabs™, 553C, Brescia, Italy) was introduced through a sterile speculum up to the distal third (dashed line) of the nasal cavity. Three complete circular movements were used to brush the nasal mucosa before withdrawal of the swab through the speculum