Core genome multilocus sequence typing schemes for epidemiological investigation of Taylorella equigenitalis and Taylorella asinigenitalis.

Researchers developed and tested a core genome multilocus sequence typing method (cgMLST) for studying the epidemiology of bacteria Taylorella equigenitalis and Taylorella asinigenitalis—causing sexual-transmitted diseases in horses and donkeys respectively. cgMLST was found to be more effective than the traditional multilocus sequence typing (MLST) in distinguishing different strains of the bacteria, improving the robustness of outbreak investigations.

Introduction and Objectives

• The study was focused on Taylorella equigenitalis—the bacterium responsible for contagious equine metritis in horses, and Taylorella asinigenitalis, mainly found in donkeys.
• The purpose of the research was to develop a better epidemiological evaluation method since the current technique, multilocus sequence typing (MLST), investigates only about 0.5% of the genome through seven genes.
• Researchers aimed to devise a more robust method termed cgMLST (core genome multilocus sequence typing) based on the larger percentage of the genome.

Methodology and Findings

• They performed the analysis with 370 T. equigenitalis and 68 T. asinigenitalis genomes belonging to multiple sequence types (STs).
• Typing was performed on 1333 loci (84.0% of the genome) from T. equigenitalis genomes, and 1255 loci (80.3% of the genome) from T. asinigenitalis genomes.
• The findings showed that cgMLST had a greater level of discrimination than conventionally used MLST. The researchers found 368 and 68 distinct core genome STs using the cgMLST method for T. Equigenitalis and T. asinigenitalis respectively versus the seven STs found by conventional MLST.
• Clustering—grouping similar items, was consistent between the MLST and cgMLST approaches. Maximum allelic distance, the maximum genetic variation between epidemiologically-related strains, was utilized to set cgMLST clustering thresholds.
• This threshold setting helped group the core genome STs into several clonal groups (CGs)—groups comprising identical genetic strains. This made cgMLST more suitable for outbreak investigations involving diseases caused by these bacterial strains.

Conclusion

• In conclusion, by using more of the genome, the cgMLST method significantly outperformed the conventional MLST method in distinguishing closely related strains of T. equigenitalis and T. asinigenitalis. In other words, the application of the cgMLST method provided a more accurate and complete understanding of the epidemiological relationships and diversity of these bacterial strains, thus lending more effectiveness to outbreak investigations.