Determination of microbial diversity in the ocular conjunctiva of healthy dogs by total DNA sequencing

Abstract

The conjunctiva plays an essential role in eye health and immunity and acts as a barrier to the entry of microorganisms. Conjunctival infections are common in dogs and result from both the invasion of pathogenic microorganisms and the uncontrolled growth of the existing microbiota. Most of the existing data come from studies based on traditional culture methods. These reports indicate the predominance of gram-positive bacteria, especially Staphylococcus spp. In the present study, we analyzed the microbiota present on the conjunctival surface from a heterogeneous dog population without ophthalmological disorders using DNA sequencing. After a thorough ophthalmological examination, conjunctival swabs were collected from both eyes of 30 dogs. After processing and nucleic acid extraction, the sample pool was subjected to shotgun DNA sequencing through the Illumina platform and analyzed via the Metagenomic Rapid Annotations using Subsystems Technology (MGRAST) server. A predominance of the phylum Proteobacteria and the genera Ralstonia and Burkholderia were identified along with a minority of fungi, whereas viruses were not found. Microbial DNA sequencing has provided new data on this subject, revealing the presence of noncultivable organisms that were previously unknown as part of the ocular microbiome.