Changes in antibiotic resistance in equine bacterial ulcerative keratitis (1991-2000): 65 horses.
Abstract: To document changes in antibiotic resistance of organisms in cases of equine bacterial ulcerative keratitis over a 10-year time period. Methods: A retrospective study. Methods: Medical records of equine patients with bacterial ulcerative keratitis seen at the University of Florida's VMTH for the years 1991-2000 were reviewed. Methods: All cases of equine bacterial ulcerative keratitis for the above mentioned years were examined. Bacterial isolates were identified and subjected to Kirby-Bauer disc diffusion method sensitivity tests. Antibiotics used in the sensitivity tests included bacitracin, ampicillin, gentamicin, chloramphenicol, polymyxin B, trimethoprim-sulfa, neomycin, kanamycin, carbenicillin, tobramycin and enrofloxacin. Results: A total of 65 bacterial isolates were subjected to sensitivity testing. Of these isolates, Pseudomonas aeruginosa accounted for 14 of the bacterial isolates (22%), Streptococcus equi subspecies zooepidemicus accounted for 13 of the bacterial isolates (20%), and Staphylococcus aureus accounted for four of the isolates (6%). A statistically significant increase in resistance of Pseudomonas aeruginosa isolates to the antibiotics gentamicin and tobramycin was found between the isolates from 1992 to 1998 and those from 1999 to 2000. An increase in resistance of Streptococcus equi subspecies zooepidemicus to gentamicin was found between the isolates from 1993 to 1997 and those from 1998 to 2000. Conclusions: Streptococcus equi subspecies zooepidemicus and Pseudomonas aeruginosa were the most common organisms isolated from cases of equine bacterial keratitis referred to the University of Florida's VMTH for the years 1991-2000. There appears to be an increase in resistance of Streptococcus equi subspecies zooepidemicus to gentamicin over the past 10 years. In addition, there is a significant increase in resistance of Pseudomonas aeruginosa to both gentamicin and tobramycin over the same time period.
Publication Date: 2003-12-03 PubMed ID: 14641828DOI: 10.1111/j.1463-5224.2003.00312.xGoogle Scholar: Lookup
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- Journal Article
Summary
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This study analyzes antibiotic resistance in bacteria causing ulcerative keratitis in horses over the course of a decade (1991-2000). The researchers found an increase in resistance to certain antibiotics in both Pseudomonas aeruginosa and Streptococcus equi subspecies zooepidemicus, the two most common organisms isolated.
Study Overview
- This is a retrospective study which examined changes in antibiotic resistance of bacteria causing ulcerative keratitis, a type of eye infection, in horses. The data was collected over a time period from 1991 to 2000 at the University of Florida’s Veterinary teaching hospital.
Methods
- The researchers conducted a retrospective review of medical records of equine patients who suffered from bacterial ulcerative keratitis between 1991 and 2000.
- They identified the bacteria causing the infections and then performed Kirby-Bauer disc diffusion method tests on them. This method tests the sensitivity of the bacteria to various antibiotics, which included bacitracin, ampicillin, gentamicin, chloramphenicol, polymyxin B, trimethoprim-sulfa, neomycin, kanamycin, carbenicillin, tobramycin and enrofloxacin.
Results
- A total of 65 bacterial isolates were tested for their sensitivity to the above-mentioned antibiotics.
- The most common bacterium found was Pseudomonas aeruginosa, making up of 22% of the isolates, followed closely by Streptococcus equi subspecies zooepidemicus at 20% and Staphylococcus aureus at 6%.
- The study found that there was a statistically significant increase in resistance of Pseudomonas aeruginosa to gentamicin and tobramycin between the years 1992-1998 and 1999-2000. Similarly, increased antibiotic resistance was observed in Streptococcus equi subspecies zooepidemicus to gentamicin during the same period.
Conclusions
- From the reduction in antibiotic sensitivity, it was inferred that there is an increase in antibiotic resistance in Pseudomonas aeruginosa and Streptococcus equi subspecies zooepidemicus over the past 10 years. This essentially implies these organisms are becoming increasingly harder to treat with the commonly-used antibiotics tested in this study.
Cite This Article
APA
Sauer P, Andrew SE, Lassaline M, Gelatt KN, Denis HM.
(2003).
Changes in antibiotic resistance in equine bacterial ulcerative keratitis (1991-2000): 65 horses.
Vet Ophthalmol, 6(4), 309-313.
https://doi.org/10.1111/j.1463-5224.2003.00312.x Publication
Researcher Affiliations
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0126, USA.
MeSH Terms
- Animals
- Anti-Infective Agents / pharmacology
- Anti-Infective Agents / therapeutic use
- Corneal Ulcer / diagnosis
- Corneal Ulcer / veterinary
- Drug Resistance, Bacterial
- Female
- Florida / epidemiology
- Gram-Negative Bacteria / drug effects
- Gram-Positive Bacteria / drug effects
- Horse Diseases / drug therapy
- Horse Diseases / epidemiology
- Horse Diseases / microbiology
- Horses
- Male
- Microbial Sensitivity Tests
- Retrospective Studies
Citations
This article has been cited 16 times.- Stolle LM, Oltmanns H, Meißner J, Heun F, Schieder AK, Wolff HT, Ohnesorge B, Busse C. Polyhexanide, Povidone-Iodine, and Hypochlorous Acid Show High In Vitro Antimicrobial Efficacy Against Pathogens Commonly Associated With Equine Infectious Keratitis. Vet Ophthalmol 2026 Jan;29(1):e70141.
- Yang L, Xie Y, Zhong G, Liu D, Zhu Y, Li J. Prevalence of antimicrobial resistance in equine-associated Pseudomonas aeruginosa: a systematic review and meta-analysis. BMC Vet Res 2025 Dec 22;22(1):44.
- Martin de Bustamante MG, Plummer CE, Caddey B, Gomez DE. The effect of topical antibiotic or antibiotic-corticosteroid treatment on the ocular surface microbiota of healthy horses. Front Microbiol 2025;16:1535095.
- Heun F, Meißner J, Schieder AK, Ohnesorge B, Busse C. Pantoea agglomerans in Equine Ulcerative Keratitis: Prevalence and Comparative Efficacy of Four Topical Antiseptics. Vet Ophthalmol 2026 Jan;29(1):e70044.
- Marchegiani A, Bazzano M, Cassarani MP, Arcelli R, Orzalesi C, Lombardo G, Lombardo M, Spaterna A, Gialletti R. Efficacy of riboflavin/UV-A corneal phototherapy as stand-alone treatment for ulcerative keratitis in horses. Vet Med (Praha) 2021 Aug;66(8):321-329.
- Ibrahim A, Abd-Elrasoul MAA, Sabra MS. Impact of pH modification of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus). BMC Vet Res 2024 May 23;20(1):218.
- Walter H, Verspohl J, Meißner J, Oltmanns H, Geks AK, Busse C. In Vitro Antimicrobial Activity of N-Acetylcysteine against Pathogens Most Commonly Associated with Infectious Keratitis in Dogs and Cats. Antibiotics (Basel) 2023 Mar 11;12(3).
- 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).
- Tahoun A, Elnafarawy HK, El-Sharkawy H, Rizk AM, Alorabi M, El-Shehawi AM, Youssef MA, Ibrahim HMM, El-Khodery S. The Prevalence and Molecular Biology of Staphylococcus aureus Isolated from Healthy and Diseased Equine Eyes in Egypt. Antibiotics (Basel) 2022 Feb 10;11(2).
- Redpath A, Hallowell GD, Bowen IM. Use of aminoglycoside antibiotics in equine clinical practice; a questionnaire-based study of current use. Vet Med Sci 2021 Mar;7(2):279-288.
- Mustikka MP, Grönthal TSC, Pietilä EM. Equine infectious keratitis in Finland: Associated microbial isolates and susceptibility profiles. Vet Ophthalmol 2020 Jan;23(1):148-159.
- Zak A, Siwinska N, Slowikowska M, Borowicz H, Ploneczka-Janeczko K, Chorbinski P, Niedzwiedz A. Conjunctival aerobic bacterial flora in healthy Silesian foals and adult horses in Poland. BMC Vet Res 2018 Aug 31;14(1):261.
- Marlo TL, Giuliano EA, Tripathi R, Sharma A, Mohan RR. Altering equine corneal fibroblast differentiation through Smad gene transfer. Vet Ophthalmol 2018 Mar;21(2):132-139.
- Hidaka S, Kobayashi M, Ando K, Fujii Y. Efficacy and safety of lomefloxacin on bacterial extraocular disease in the horse. J Vet Med Sci 2015 Jul;77(7):829-35.
- Hellander-Edman A, Makdoumi K, Mortensen J, Ekesten B. Corneal cross-linking in 9 horses with ulcerative keratitis. BMC Vet Res 2013 Jun 26;9:128.
- Czerwinski SL, Lyon AW, Skorobohach B, Léguillette R. Pharmacokinetic analysis of topical tobramycin in equine tears by automated immunoassay. BMC Vet Res 2012 Aug 21;8:141.
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