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Background: Three horse mares inadvertently inseminated with semen from a Tayorella asinigenitalis‐positive Jack donkey developed severe, purulent endometritis whereas two Jenny donkeys mated naturally to the same Jack donkey did not develop clinical signs of infection. Objectives: To isolate and identify the causative agent. Study design: Case report. Methods: Endometrial swabs from the infected mares were cultured on selective and non‐selective media under aerobic and microaerophilic conditions. Isolates were subjected to Gram staining, oxidase and catalase tests, the Monotayl Latex Agglutination test and PCR to test for both T. equigenitalis and T. asinigenitalis. In vitro antimicrobial susceptibility testing was performed and the bacterial isolate was genotyped using MLST. Results: A new sequence type of T. asinigenitalis was confirmed. Main limitations: A limited numbers of mares and donkeys are described. Conclusions: This strain of T. asinigenitalis causes a severe venereal infection in mares but not in Jenny donkeys. [ABSTRACT FROM AUTHOR]

In 2018, a T. asinigenitalis strain (MCE663) was isolated in a Persian onager tested for contagious equine metritis (CEM) in a United Kingdom (UK) zoo. This bacterium had never been reported in the UK and Multilocus Sequence Typing described a new atypically divergent ST (ST60). Although the causative agent of CEM is the bacterium Taylorella equigenitalis , a first natural outbreak of endometritis caused by T. asinigenitalis ST70 was reported in 2019, putting its pathogenic potential into question. In this context, we aimed to further sequence the T. asinigenitalis MCE663 genome and characterize the strain using phenotypical and genetic approaches. Results showed that it gathered all identification characteristics of T. asinigenitalis with smaller colonies and it was susceptible to all tested antibiotics. Genome-level phylogeny showed that the genome MCE663 formed a distinct phylogroup, and only shared ≈ 96.1% of average nucleotide identity (ANI) with the three published T. asinigenitalis genomes, which together shared ≈ 98.3% ANI. According to current cut-offs consensus for species and subspecies delineation (95% and 98%, respectively), our results support the first insights of a sublineage delineation within the T. asinigenitalis species. • Genome of a T. asinigenitalis isolated from a Persian onager in 2018 was sequenced. • This genome (MCE663) showed atypical genetic distance from those already published. • MCE663 genome analysis suggests sublineages within the T. asinigenitalis species. [ABSTRACT FROM AUTHOR]

Misidentification between Taylorella equigenitalis , the causative agent of contagious equine metritis (CEM), and Taylorella asinigenitalis is observed by the gold standard culture method. The performance of matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS) for Taylorella species identification was evaluated using 85 T. equigenitalis and 28 T. asinigenitalis strains selected on the basis of multilocus sequence typing data. Seven of the T. equigenitalis and 9 of the T. asinigenitalis strains were used to generate in-house reference spectra to expand the existing commercial Bruker database. Two bacterial incubation times and 3 different sample preparation procedures were compared. Overall, we demonstrated the usefulness of MALDI-TOF MS as a differential diagnostic tool for CEM; however, commercial spectra databases should be expanded with T. asinigenitalis reference spectra to achieve the expected performance. Moreover, direct spotting of 48-h colonies was not only the most efficient protocol but also the easiest to implement in a clinical setting. • An assessment of the reliability of MALDI-TOF MS for the identification of Taylorella species is presented. • Different bacterial incubation times and sample preparation procedures are compared. • Species-level identification of Taylorella equigenitalis is demonstrated. • Species-level identification of Taylorella asinigenitalis is demonstrated when the Bruker database is expanded with in-house T. asinigenitalis reference spectra. [ABSTRACT FROM AUTHOR]