Pooling of genital swabs for detection by PCR of Taylorella equigenitalis, the cause of contagious equine metritis.

The research study attempts to validate a cost-effective method for detecting Taylorella equigenitalis, the bacteria causing contagious equine metritis in horses, by combining multiple genital swabs for one PCR test instead of individual tests.

Research Objective

The study aims to evaluate the efficacy of pooling genital swabs for a single polymerase chain reaction (PCR) test rather than conducting individual tests for each swab when screening horses for T. equigenitalis infection.

Methods

Previously gathered PCR signal strengths (Ct values) from 149 PCR positive genital swabs and historical data on the expected number of positive swabs in a set were used in this study. A total of 24 sets of four equine genital swabs were tested. These sets were composed in the lab using one or more T. equigenitalis positive swabs from naturally infected cases. To resemble a typical range of PCR Ct values expected during real case scenarios, positive and negative swabs were carefully chosen. The pooled swabs were tested using an established PCR method.

• The study used an in vitro method, examining the samples in a controlled environment outside of a living organism.
• The researchers studied 24 sets of four equine genital swabs which were prepared in a laboratory setting.

Results

The study found that despite a slight decrease in Ct value when pooling one positive swab with three negative ones, all pools remained distinctively positive.

Conclusions

The research concluded that swab pooling method could effectively detect T. equigenitalis infection with a similar detection level to its individual testing counterpart. The method has the added benefit of being a more affordable alternative due to its ability to test more samples with fewer tests. However, the study acknowledged its limitation, stating that large numbers of field positive horses are not readily available, but affirmed the effectiveness of the technique using a lab-generated “proof of concept” approach. Therefore, the swab pooling strategy offers a feasible and cost-saving approach to field cases.