Comparison of culture versus quantitative real-time polymerase chain reaction for the detection of Taylorella equigenitalis in field samples from naturally infected horses in Canada and Germany.

A quantitative real-time polymerase chain reaction method (qPCR) was developed and tested for the detection of Taylorella equigenitalis. It was shown to have an analytical sensitivity of 5 colony-forming units (CFU) of T. equigenitalis when applied to the testing of culture swabs that mimicked field samples, and a high analytical specificity in not reacting to 8 other commensal bacterial species associated with horses. As designed, it could also differentiate specifically between T. equigenitalis and T. asinigenitalis. The qPCR was compared to standard culture in a study that included 45 swab samples from 6 horses (1 stallion, 5 mares) naturally infected with T. equigenitalis in Canada, 39 swab samples from 5 naturally infected stallions in Germany, and 311 swab samples from 87 culture negative horses in Canada. When the comparison was conducted on an individual sample swab basis, the qPCR had a statistical sensitivity and specificity of 100% and 96.4%, respectively, and 100% and 99.1% when the comparison was conducted on a sample set basis. A comparison was also made on 203 sample swabs from the 5 German stallions taken over a span of 4 to 9 mo following antibiotic treatment. The qPCR was found to be highly sensitive and at least as good as culture in detecting the presence of T. equigenitalis in post-treatment samples. The work demonstrates that the qPCR assay described here can potentially be used to detect the presence of T. equigenitalis directly from submitted sample swabs taken from infected horses and also for determining T. equigenitalis freedom following treatment.