Whole genome sequences of nine Taylorella equigenitalis strains isolated in the Czech Republic between 1982-2021: Molecular dating suggests a common ancestor at the time of Roman Empire.
Authors: Hrala Matěj, Andrla Petr, Bosák Juraj, Fedrová Pavla, Mugutdinov Amir, Karpíšková Renata, Nedbalcová Kateřina, Raichová Jitka, Faldyna Martin, Hořín Petr, Šmajs David
Journal: PloS one
Summary
Contagious equine metritis, caused by *Taylorella equigenitalis*, causes significant reproductive losses in mares through endometritis and temporary infertility, yet the evolutionary trajectory and antibiotic resistance patterns of this pathogen have remained poorly characterised until now. Czech researchers sequenced nine complete genomes of *T. equigenitalis* isolates collected from Kladruber horses between 1982 and 2021, complementing these with 18 publicly available sequences to map resistance emergence and evolutionary timescales across European populations. A striking finding was the recent acquisition of streptomycin resistance in contemporary strains, with all isolates from 1982–2018 remaining susceptible whilst modern isolates showed resistance, indicating this resistance mutation emerged within the last few years rather than representing an ancient trait. Molecular dating of the combined dataset suggested all analysed strains shared a common ancestor approximately 1,500–2,600 years ago (broadly consistent with the Roman period), with the pathogen evolving at a rate of 6.9×10⁻⁷ substitutions per site annually, and Czech genomes clustering closely with Austrian strains. For practitioners, these findings underscore the importance of antibiotic surveillance protocols and the urgent need to evaluate alternative therapeutic strategies for breeding programmes, particularly given that streptomycin susceptibility testing may no longer be a reliable indicator of treatment success in recently infected animals.
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Practical Takeaways
- •Streptomycin is no longer a reliable treatment option for contagious equine metritis in Czech populations; alternative antibiotic protocols should be reviewed and implemented
- •Continued antibiotic surveillance and genomic monitoring of T. equigenitalis is essential to track emerging resistance patterns and inform treatment recommendations
- •Mare screening protocols should remain rigorous as this pathogen continues to evolve; consider regional resistance patterns when choosing prophylactic or therapeutic approaches
Key Findings
- •Contemporary Taylorella equigenitalis strains from Czech Kladruber horses show streptomycin resistance, whereas historical strains (1982-2018) were streptomycin-susceptible, indicating recent emergence of this resistance
- •Molecular dating of 27 T. equigenitalis strains suggests a common ancestor 1.5-2.6 thousand years ago (first centuries A.D.)
- •Genome substitution rate calculated at 6.9×10⁻⁷ substitutions per site per year for T. equigenitalis
- •Czech T. equigenitalis strains show genetic similarity to Austrian strains, supporting regional epidemiological links