Abstract
The ocular surface microbiome of veterinary species has not been thoroughly characterized using molecular-based techniques, such as next generation sequencing (NGS), as the vast majority of studies have utilized traditional culture-based techniques. To date, there is one pilot study evaluating the ocular surface of healthy dogs using NGS. Furthermore, alterations in the ocular surface microbiome over time and after topical antibiotic treatment are unknown. The objectives of this study were to describe the bacterial composition of the ocular surface microbiome in clinically normal dogs, and to determine if microbial community changes occur over time or following topical antibiotic therapy. Topical neomycin-polymyxin-bacitracin ophthalmic ointment was applied to one eye each of 13 adult dogs three times daily for seven days, while contralateral eyes served as untreated controls. The inferior conjunctival fornix of both eyes was sampled via swabbing at baseline prior to antibiotic therapy (day 0), after 1 week of treatment (day 7), and 4 weeks after discontinuing treatment (day 35). Genomic DNA was extracted from the conjunctival swabs and primers targeting the V4 region of bacterial 16S rRNA genes were used to generate amplicon libraries, which were then sequenced on an Illumina platform. Data were analyzed using Quantitative Insights Into Molecular Ecology (QIIME 2.0). At baseline, the most relatively abundant phyla sequenced were Proteobacteria (49.7%), Actinobacteria (25.5%), Firmicutes (12%), Bacteroidetes (7.5%), and Fusobacteria (1.4%). The most common families detected were Pseudomonadaceae (13.2%), Micrococcaceae (12%), Pasteurellaceae (6.9%), Microbacteriaceae (5.2%), Enterobacteriaceae (3.9%), Neisseriaceae (3.5%), and Corynebacteriaceae (3.3%). Alpha and beta diversity measurements did not differ in both control and treatment eyes over time. This report examines the temporal stability of the canine ocular surface microbiome. The major bacterial taxa on the canine ocular surface remained consistent over time and following topical antibiotic therapy.
Highlights
The ocular surface microbiota consists of microorganisms residing on the corneoconjunctival surface and within the tear film
The canine eye is susceptible to ocular surface diseases such as keratoconjunctivitis sicca and infectious ulcerative keratitis, which are often treated with topical broad-spectrum antibiotics such as neomycin-polymyxin-bacitracin [1,2,3,4,5,6,7]
This study aimed to describe the bacterial compostition of the ocular surface microbiome in healthy privately-owned dogs, and to determine if microbial community changes occur over time or following topical antibiotic therapy
Summary
The ocular surface microbiota consists of microorganisms residing on the corneoconjunctival surface and within the tear film. Changes in the composition of the ocular surface microbiota may be associated with ocular surface disease, as evidence suggests these commensal microorganisms protect the eye against the proliferation of opportunistic and pathogenic species [8,9]. The percent of total positive cultures from healthy canine eyes was low, ranging from 29–45%, with Gram-positive bacteria such as Staphylococcus, Streptococcus, Bacillus, and Micrococcus spp. most commonly isolated regardless of geography or climate [3,5,7,14,15,16]. Gram-negative bacteria were less frequently cultured, with Pseudomonas, Moraxella, Acinetobacter, Neisseria, E. coli, Klebsiella, and Enterococcus spp. comprising less than 4% of isolates [3,5,7,14,15,16]
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