In vitro susceptibility patterns of Aspergillus and Fusarium species isolated from equine ulcerative keratomycosis cases in the midwestern and southern United States with inclusion of the new antifungal agent voriconazole.

The research aimed to determine the effectiveness of various antifungal treatments on Aspergillus and Fusarium species – the causative organisms of equine ulcerative keratomycosis. The study found that voriconazole was the most effective antifungal agent against these organisms in the midwestern and southern United States, outperforming natamycin, itraconazole, fluconazole, and ketoconazole in terms of susceptibility. The geographical location did not affect the patterns of antifungal susceptibility.

Procedure and Methodology

• The research used banked fungal isolates from equine corneal ulcers. These included eight Aspergillus species and six Fusarium species which were identified at The University of Texas Health Science Center at San Antonio.
• The minimum inhibitory concentration was determined for each isolate. This is the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation.
• The susceptibility to natamycin, fluconazole, itraconazole, voriconazole, ketoconazole, and miconazole were also tested for each fungal isolate.

Results and Findings

• The study found that the fungi were significantly more susceptible to voriconazole than to natamycin, itraconazole, fluconazole, and ketoconazole. Miconazole susceptibility did not significantly differ from that of voriconazole.
• Aspergillus species showed the highest susceptibility to voriconazole, miconazole, and itraconazole, which was significantly better than fluconazole and ketoconazole.
• Fusarium species showed the greatest susceptibility to natamycin and voriconazole, but were least susceptible to itraconazole and ketoconazole.
• The study also compared the susceptibility of the isolates from different states and found no significant differences.

Conclusion

• The research concluded that voriconazole appears to be the most effective antifungal agent for the initial treatment of equine keratomycosis in the midwestern and southern United States.
• The study’s results are comparable with previous ones as they both show that fungi isolated from equine keratomycosis cases consistently show poor susceptibility to fluconazole.
• The geographical location of the isolates within the midwestern and southern United States did not show significant differences in the patterns of antifungal susceptibility.