In vitro efficacy of an ophthalmic drug combination against corneal pathogens of horses.

This research article focuses on the testing of a combination of ophthalmic drugs against corneal pathogens commonly found in horses. The research found that the combinational drug was as effective as, or in some cases more effective than, each individual drug applied separately.

Methods of Research

In this study, they identified and isolated three bacterial and two fungal corneal pathogens from horses. They tested these pathogens using a Minimum Inhibitory Concentration (MIC) method. This method helps to determine the lowest concentration of the drug combination that can prevent the growth of these pathogens.

• The drug combination consisted of equal volumes of natamycin 3.33%, tobramycin 0.3%, cefazolin 5.5%, and equine serum.
• The proteinase-inhibitory activity of the combination was assessed with a fluorescence microplate assay, using gelatin and collagen I as substrates.
• They compared the MICs of the combined drug to those of each individual medication.
• Two statistical methods – paired t tests and a 2-way ANOVA were used to compare antiproteinase activity of the drug combination and serum.

Results of the Research

The study found that the combined drug was equally, and sometimes more, effective at inhibiting microbial growth of all tested pathogens than using each medication separately.

• It was significantly more effective against B-hemolytic Streptococcus spp, Aspergillus spp, and Fusarium spp.
• Both the serum and the drug combination exhibited substantial antigelatinase activity, while the serum showed significant anticollagenase activity.
• The antiproteinase activity of the serum was concentration-dependent, which allowed the serum to have a greater activity than the drug combination after 3.5 and 4 hours in the gelatin and collagen I assays, respectively.

Conclusions of the Research

The study concluded that drug combinations offer the benefit of reducing the time, stress, and fatigue associated with topical treatments that involve multiple individual drugs. This is particularly relevant for horses exhibiting keratitis, an inflammation of the cornea, which these drugs are intended to treat.