Antimicrobial Activity of Equine Semen Extenders Against Taylorella equigenitalis

Abstract

Taylorella equigenitalis is a gram negative coccobacillus and the causative agent of a transmissible venereal disease in horses known as contagious equine metritis (CEM). This disease can be responsible for significant economic loss as a result of decreased fertility and increased rigidity of international controls on shipment of horses and equine germplasm. Outbreaks of this disease have been documented in various countries since 1977, with the most recent discovery of CEM in the United States in December 2008. During disease occurrences / outbreaks, culturing semen samples for T. equigenitalis prior to breeding may help to prevent transmission of this disease; however, little is known about the antimicrobial activity of equine semen extenders against the organism. The purpose of this study was to investigate the infectivity levels of T. equigenitalis in several equine semen extenders inoculated with known concentrations of the organism. The semen extenders used included INRA 96�, E-Z Mixin BF�, and VMDZ�. In addition, Timentin� was added to INRA 96� at three different concentrations (0.5, 1.0, and 1.5 mg/mL) to further investigate synergistic effects of antibiotic supplementation to extenders. Results were based on visually counting colonies on chocolate Eugon agar plates. Both INRA 96� with added Timentin� and VMDZ� (as supplied by the manufacturer) significantly reduced the numbers of T. equigenitalis isolated from semen extenders compared to INRA 96� (as supplied by the manufacturer) or the antibiotic free E-Z Mixin BF�. Our findings indicate that INRA 96� with Timentin� added or VMDZ� may significantly decrease the growth of T. equigenitalis in extended semen, however, it is also important to consider possible effects on sperm longevity and fertility while decreasing seminal pathogens.