Antimicrobial susceptibility patterns of fungi isolated from horses with ulcerative keratomycosis.

The research investigated the effectiveness of various antifungal medications against fungi found in horses suffering from ulcerative keratomycosis, a fungal infection of the cornea, in Florida. The study highlights that initial antifungal therapy involving topically applied natamycin, miconazole, itraconazole, or ketoconazole is suggested for management of such infections.

Objective and Methods

• The main objective of the research was to assess the susceptibility of various fungal isolates from infected horses’ eyes to topically applied antifungal medications. This was done using measurements of minimum inhibitory concentration (MIC) and 50% inhibitory concentration (IC50%).
• The researchers also compared their results with findings from other studies to determine if susceptibility patterns vary among fungal strains in different geographic locations.
• The study utilized corneal fungal cultures from 22 horses with ulcerative keratomycosis in Florida. These cultures were plated on specific types of agar, which is used for growing microbial cultures in the lab.
• The fungal cultures were tracked for growth on a weekly basis for a total of 30 days. MIC and IC50% for a variety of antifungal drugs were measured for each fungal isolate.

Results and Findings

• The study detected a variety of fungal species in the cultures, with the highest prevalence of Aspergillus and Fusarium species.
• The results demonstrated that all the fungi were most susceptible to natamycin and miconazole, followed by itraconazole and ketoconazole. No significant difference was found among these drugs.
• However, the fungi were substantially less susceptible to fluconazole, a frequently used antifungal medication.

Conclusions

• Based on their findings, the researchers suggest that initial antifungal therapy for ulcerative keratomycosis in horses should involve topical application of natamycin, miconazole, itraconazole, or ketoconazole.
• The treatment should be based on a range of factors, including the horse’s medical history, results of ophthalmic examination, cytologic findings, isolation of the pathogenic fungus, and known prevalence of unique ocular fungi in the specific geographic area.
• Antifungal susceptibility testing in the lab can be beneficial in understanding the pharmacologic susceptibility patterns of fungi in different regions, thereby better informing treatment decisions.