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SUMMARY
Objectives
To evaluate in vitro susceptibility to topical antifungal medications, as measured by minimum inhibitory concentration (MIC) and 50% inhibitory concentration (IC50%), of fungal isolates from horses with ulcerative keratomycosis in Florida; to compare results with those of other studies to identify differences in susceptibility patterns among fungi isolated from horses in different geographic regions; and to note indications of fungal resistance to drugs tested in other studies.
Sample Population
Corneal fungal cultures from client-owned horses from Florida with ulcerative keratomycosis (n = 22).
Procedure
Fungal cultures were plated on Emmons modified Sabouraud dextrose agar and mycobiotic agar, examined weekly for growth, and kept for a total of 30 days. In vitro MIC and IC50% of fluconazole, itraconazole, ketoconazole, miconazole, and natamycin were measured for each fungal isolate.
Results
Aspergillus (n = 9; 41%), Fusarium (7; 32%), Penicillium (2; 9%), Cylindrocarpon (1; 4%), Scytalidium (1; 4%), and Torulopsis (1; 4%) spp and an unidentified yeast (1; 4%) were isolated. Fungi were most susceptible to antifungal drugs in the following order: natamycin and miconazole equally, itraconazole, and ketoconazole, although no significant difference was found among drugs. Fungi were significantly less susceptible to fluconazole (P < 0.0001) than to the other 4 drugs.
Conclusions
Initial antifungal therapy with topically applied natamycin, miconazole, itraconazole, or ketoconazole is recommended for ulcerative keratomycosis in horses in the subtropical environment of Florida.
Clinical Relevance
Specific antifungal treatment of horses with ulcerative keratomycosis should be based on history, results of ophthalmic examination, cytologic findings, isolation of the pathogenic fungus, and known prevalence of unique ocular fungi in specific geographic areas. In vitro antifungal susceptibility testing may be most beneficial in aiding documentation of pharmacologic susceptibility patterns of fungi in specific geographic regions. (Am J Vet Res 1998; 59:138–142)
fungal organisms than ketoconazole and fluconazole and is highly effective against Aspergillus spp. 21,25,26 Itraconazole is also reportedly effective for treatment of clinical equine keratomycosis. 25 Voriconazole, a new azole antifungal, has been
of the eye in humans and rabbits after oral and topical admin-istration. 35,36 These factors suggest that voriconazole may provide an improved treatment option for keratomycosis in horses. The purpose of this study was to evaluate the ocular
effects on the aerobic bacterial and fungal conjunctival flora of normal thoroughbred brood mares in Florida . Vet Ophthalmol 2003 ; 6 : 45 – 50 . 10.1046/j.1463-5224.2003.00265.x 2 Barton MH . Keratomycosis . Compend
, Alternaria spp , Fusarium spp, and Cladosporium spp. 2,4 The most commonly isolated fungi from the cornea of horses with keratomycosis are Aspergillus spp , Penicillium spp , Cladosporium spp , and Alternaria spp, although there are numerous
-Shlomo G , Plummer C , Barrie K , Brooks D . Curvularia keratomycosis in a dog . Vet Ophthalmol . 2010 ; 13 ( 2 ): 126 – 130 . doi: 10.1111/j.1463-5224.2010.00766.x
Avariety of systemic or localized fungal infections in horses has been described including keratomycosis, endophthalmitis, meningitis, mycosis of the auditory tube diverticula, metritis, rhinitis, and dermatitis. 1-8 Effective antifungal
Although there are occasional descriptions of fungal keratitis in several domestic animal species, 1–7 keratomycosis is reported to occur frequently only in horses. 8–10 The higher prevalence of fungal keratitis in horses is speculated to result
Objective
To compare initial clinical appearances, healing mechanisms, risk factors, and outcomes of horses with fungal keratitis.
Design
Retrospective analysis.
Animals
52 horses (53 eyes) with fungal keratitis.
Procedure
Medical records and clinical photographs of eyes were reviewed. Keratomycoses were categorized on the basis of clinical appearance at initial examination and pattern of healing.
Results
Five distinct forms of mycotic keratitis were recognized. Of 53 affected eyes, 34 (64%) retained sight and had varying degrees of corneal scarring after treatment, 6 (11%) had a cosmetic appearance but were blind, and 13 (25%) were enucleated. Bacterial-like ulcers were the most frequent type and the most difficult for predicting outcome. Eyes affected by superficial fungal keratitis were likely to be chronically infected and to require debridement and extended treatment but usually healed with minimal scarring. Keratomycosis with a surrounding furrow resulted in a grave prognosis. Aspergillus organisms were isolated from 9 of 10 such eyes. Cake-frosting material was a positive prognostic sign. Fungal corneal stromal abscesses tended to be caused by yeast.
Clinical Implications
This information will aid practitioners in recognizing various forms of fungal keratitis and guide them when making therapeutic decisions and prognoses for affected horses. (J AM Med Assoc 1998;213:105-112)
associated with keratomycosis are circumvented with IVCM, including the slow growth rate of some fungi in vitro, difficulties obtaining representative samples in an atraumatic manner from deep corneal stromal lesions, and the ubiquitous nature of many common