Evaluation of the bacterial ocular surface microbiome in clinically normal horses before and after treatment with topical neomycin-polymyxin-bacitracin.
Abstract: Next generation sequencing (NGS) studies have demonstrated a rich and diverse ocular surface-associated microbiota in people that was previously undetected by traditional culture-based methods. The ocular surface microbiome of horses has yet to be investigated using NGS techniques. This study aimed to determine the bacterial composition of the ocular surface microbiome in healthy horses, and to identify whether there are microbial community changes over time and following topical antibiotic use. One eye of 12 horses was treated 3 times daily for 1 week with neomycin-polymyxin-bacitracin ophthalmic ointment. Contralateral eyes served as untreated controls. The inferior conjunctival fornix of both eyes was sampled at baseline prior to initiating treatment (day 0), after 1 week of treatment (day 7), and 4 weeks after concluding treatment (day 35). Genomic DNA was extracted from ocular surface swabs and sequenced using primers that target the V4 region of bacterial 16S rRNA. At baseline, the most abundant phyla identified were Proteobacteria (46.1%), Firmicutes (24.6%), Actinobacteria (12.6%), and Bacteroidetes (11.2%). The most abundant families included Pasteurellaceae (13.7%), Sphingomonadaceae (7.9%), an unclassified Order of Cardiobacteriales (7.7%), and Moraxellaceae (4.8%). Alpha and beta diversity measurements were unchanged in both treatment and control eyes over time. Overall, the major bacterial taxa on the equine ocular surface remained stable over time and following topical antibiotic therapy.
Publication Date: 2019-04-03 PubMed ID: 30943258PubMed Central: PMC6447178DOI: 10.1371/journal.pone.0214877Google Scholar: Lookup
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- Journal Article
Summary
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The research article explores the microbial composition of the ocular surface in healthy horses, scrutinizes the changes therein over time and following the application of a topical antibiotic.
Research Methodology
- The study engaged 12 horses as subject samples. One eye of each horse was treated thrice daily for a week with an ophthalmic antibiotic ointment neomycin-polymyxin-bacitracin. The other eye was left untreated to serve as a control variable in the experiment.
- The bacteria from the inferior conjunctival fornix of both eyes were sampled thrice; at the outset of the treatment, after one week of continued treatment, and four weeks after the conclusion of the treatment.
- Genomic DNA was extracted from the ocular surface swabs gathered during these samplings and sequenced using primers specifically targeting the V4 region of bacterial 16S rRNA to identify the bacterial composition.
Findings
- The initial baseline showed the ocular surface’s bacterial composition to be made primarily of Proteobacteria (46.1%), Firmicutes (24.6%), Actinobacteria (12.6%), and Bacteroidetes (11.2%).
- At the family level, Pasteurellaceae made up 13.7%, Sphingomonadaceae constituted 7.9%, an unclassified Order of Cardiobacteriales accounted for a 7.7% share, whereas Moraxellaceae contributed a smaller 4.8%.
- The alpha and beta diversity measurements that indicate microbial diversity on the eye surface remained the same over the sampling period in both the treated and control eyes.
- Overall, the major bacterial taxa on the equine ocular surface stayed constant over time even after repeated application of the topical antibiotic therapy.
Conclusion
- This study distinguished the bacterial composition of the ocular surface microbiome in healthy horses with the support of next-generation sequencing (NGS) methods.
- It proved that the ocular surface’s bacterial composition remains stable over time and is not affected by the administration of topical antibiotic therapy.
- The results can be important for better understanding the ocular immune system and can have significant clinical implications in veterinary ophthalmology.
Cite This Article
APA
Scott EM, Arnold C, Dowell S, Suchodolski JS.
(2019).
Evaluation of the bacterial ocular surface microbiome in clinically normal horses before and after treatment with topical neomycin-polymyxin-bacitracin.
PLoS One, 14(4), e0214877.
https://doi.org/10.1371/journal.pone.0214877 Publication
Researcher Affiliations
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America.
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America.
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America.
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America.
MeSH Terms
- Administration, Ophthalmic / veterinary
- Animals
- Anti-Bacterial Agents / administration & dosage
- Bacitracin / administration & dosage
- Bacteria / drug effects
- Bacteria / genetics
- Conjunctiva / drug effects
- Conjunctiva / microbiology
- Horses / microbiology
- Microbiota / drug effects
- Microbiota / genetics
- Neomycin / administration & dosage
- Polymyxins / administration & dosage
Conflict of Interest Statement
The authors have declared that no competing interests exist.
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Citations
This article has been cited 7 times.- Julien ME, Shih JB, Correa Lopes B, Vallone LV, Suchodolski JS, Pilla R, Scott EM. Alterations of the bacterial ocular surface microbiome are found in both eyes of horses with unilateral ulcerative keratitis.. PLoS One 2023;18(9):e0291028.
- Santibáñez R, Lara F, Barros TM, Mardones E, Cuadra F, Thomson P. Ocular Microbiome in a Group of Clinically Healthy Horses.. Animals (Basel) 2022 Apr 7;12(8).
- Foote BC, Smith JS, Bowden AC, Allbaugh RA, Sebbag L. Case Report: Successful Management of Refractory Keratomycosis in an Alpaca Using Penetrating Keratoplasty and Combination Antifungal Therapy (Caspofungin 0.5% and Terbinafine 1%).. Front Vet Sci 2021;8:644074.
- Leis ML, Madruga GM, Costa MO. The porcine corneal surface bacterial microbiome: A distinctive niche within the ocular surface.. PLoS One 2021;16(2):e0247392.
- Walsh ML, Meason-Smith C, Arnold C, Suchodolski JS, Scott EM. Evaluation of the ocular surface mycobiota in clinically normal horses.. PLoS One 2021;16(2):e0246537.
- Rogers CM, Scott EM, Sarawichitr B, Arnold C, Suchodolski JS. Evaluation of the bacterial ocular surface microbiome in ophthalmologically normal dogs prior to and following treatment with topical neomycin-polymyxin-bacitracin.. PLoS One 2020;15(6):e0234313.
- Darden JE, Scott EM, Arnold C, Scallan EM, Simon BT, Suchodolski JS. Evaluation of the bacterial ocular surface microbiome in clinically normal cats before and after treatment with topical erythromycin.. PLoS One 2019;14(10):e0223859.
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