Nasal microbiota profiles are similar at two swabbing depths in healthy awake dogs

The nasal microbiome may play an important role in dogs’ olfaction, as microbial communities in the nasal cavity can directly interact with the olfactory epithelium. Previous studies have used various sampling methods and depths to examine the canine nasal microbiota and the effect of sampling depth on the detected nasal microbiota remains unclear. To address this, we investigated and compared the nasal microbiota of 81 awake family dogs, sampled at two swabbing depths (15 mm and 25 mm) of the left nostril in the same individuals. The most abundant bacterial taxa in our nasal samples belonged to Moraxella ( Gammaproteobacteria ), consistent with previous studies. The 15 mm samples had a higher Shannon Diversity Index compared to the 25 mm samples, indicating closer proximity to the external environment. However, we found no significant differences in richness and overall microbiota composition between the two sampling depths. These results indicate that bacterial community profiles within the anterior nasal cavity are similar at the two examined depths. Because the deeper sample was always collected first from the same nostril, potential order effects cannot be excluded. Nevertheless, based on the findings, we recommend using a sampling depth up to 15 mm when examining the nasal microbiota of healthy awake mesocephalic dogs in field settings, as it is less invasive and minimises discomfort.