The development of a new selective medium for isolation of Taylorella sp.

Abstract

The objective of this study was to develop an improved selective medium for the isolation of Tay/ore/la sp .. It is important the United States remains free of contagious equine metritis, because large sums of money could be lost in the Thoroughbred industry if this organism is not easily detected. The currently used selective medium, Modified Timoney Shin (MTS), is too restrictive for growing some strains of Tay/ore/la sp. A new selective media that is more restrictive to growth of contaminants would ensure that laboratory personnel are able to isolate Tay/ore/la sp. more readily from diagnostic samples. A total of eighty-seven antimicrobials were evaluated using a disk diffusion test, and ten antimicrobials with the smallest mean zones of inhibition for Tay/ore/la sp. over three replications were chosen for inclusion in this study. The zones of inhibition of Tay/ore/la equigenitalis strains were significantly larger than the zones of inhibition of Tay/ore/la asinigenitalis strains for some of the antimicrobials. Combinations of antimicrobials were evaluated, and final selections were based on the maximum number of contaminants inhibited and on the ability to support the growth of T. equigenita/is and T. asinigenita/is. The combination of 320 µg/ml paminosalicyclic acid, 5 µg/ml clindamycin, and 5 µg/ml amphotericin B supported the growth of Tay/ore/la sp., but was more inhibitory to the ten most frequent contaminants than was MTS. Ten individual contaminants and sixteen combinations of a single dilution of contaminants with Tay/ore/la sp. included in lower dilutions were plated onto the new medium and MTS. Fourteen contaminants were more inhibited on the new medium than on MTS, eleven had comparable growth on both, and there was one that grew better on the new medium. Twenty-two swabs from caudal reproductive tracts of horses were evaluated.Sixteen had less growth on the new medium than on MTS, four had comparable growth, and V two had more growth. A side by side comparison of the new media with MTS will be necessary to evaluate its potential to replace MTS in diagnostic testing.antifungal agent and two antibiotics, is too restrictive for growth of some strains of Tay/ore/la sp.Under the present system, the United States National Veterinary Services Laboratories (NVSL) approves state and university diagnostic laboratories for conducting CEM testing on imported horses. Swabs from mares (cervix, clitoral fossa, and clitoral sinus) and stallions (urethra, urethral fossa, and penile sheath) are submitted to diagnostic laboratories for culture. The horses are held in quarantine stations until testing is completed. If Tay/ore/la sp. are detected, horses must be treated under a specific regimen and retested before they are released, or they must be returned to the country of origin. If carrier horses were missed due to inadequate bacteriologic culture, very expensive epidemiologic tracing would be required to assure that all potentially exposed horses were tested . Development of a new selective medium which would inh...