How to Diagnose Common Equine Reproductive Tract Bacterial Pathogens Using Chromogenic Agar

1. Introduction
The most common microbiological pathogens of reproductive tract disease in the horse are Streptococcus sp., Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Pseudomonas aeruginosa. The standard approach to the detection of these pathogenic bacteria is to culture the reproductive tracts of the mare or stallion. One or more general purpose media such as horse blood agar (HBA) or MacConkey agar are inoculated before aerobic incubation occurs at 37°C for 24–48 h. The identification of pathogenic bacteria has been based on colony size, morphology, pigmentation, hemolytic patterns, and gram-stain. Such colonial characteristics rarely permitted more than a presumptive identification, and biochemical and/or serological tests are required for definitive diagnosis. This approach frequently necessitates the testing of commensal bacteria that resemble pathogens,¹  which may be more expensive and labor intensive, especially in a veterinary practice trying to make accurate and expedient bacterial diagnoses. [...]