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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]

• T. equigenitalis (Te) viability was assessed in 11 commercial transport systems. • Viability at ambient temperature was inferior to refrigeration at 1–2 days. • Four of 11 swab systems were superior for viability but qPCR results were similar. • A liquid transport medium for mycoplasmas and viruses (UTM) was assessed. • UTM was superior to Amies charcoal gel for Te viability during 10-day refrigeration. The cultural diagnosis of the causal agent of contagious equine metritis (Taylorella equigenitalis) using transport swabs is challenging. Swabs must be placed in Amies charcoal medium, refrigerated during transport, and plated out at the laboratory no later than 48 h after sampling. In this study, the viability of T. equigenitalis strain CIP 79.7T in 11 commercial swab transport systems was initially compared at 1 day and 2 days of storage at ambient (20 ± 3 °C) or refrigerated (5 ± 3 °C) temperature. The four best swab transport systems, systems B, E, F (used as the reference) and K, were then compared at 0, 2, 3, 4, 7 and 10 days at refrigerated temperatures. Statistically significant differences were observed after 10 days only for system K compared to the reference, with approximately 95% viable T. equigenitalis recovered in system K compared to approximately 77% in system F. System K is thus promising for preservation and transport of viable T. equigenitalis for culture. [ABSTRACT FROM AUTHOR]

• Identification of three major and three minor clonal complexes and 11 singletons in European T. equigenitalis population. • Emergence of several STs with cross-border circulation, in particular ST16 and ST46 from the major complexes CC2 and CC8. The accurate identification of Taylorella equigenitalis strains is essential to improve worldwide prevention and control strategies for contagious equine metritis (CEM). This study compared 367 worldwide equine strains using multilocus sequence typing according to the geographical origin, isolation year and equine breed. The strains were divided into 49 sequence types (STs), including 10 described for the first time. Three major and three minor clonal complexes (CCs), and 11 singletons, were identified. The genetic heterogeneity was low (0.13 STs/strain) despite the wide diversity of geographical origins (n = 16), isolation years (1977–2018) and equine breeds (n = 18). It was highest outside Europe and in the 1977–1997 period; current major STs and CCs already existed before 1998. Previous data associated the major CC1 with the first CEM outbreaks in 1977–1978 in the United Kingdom, Australia and the United States, and revealed its circulation in France. Our study confirms its circulation in France over a longer period of time (1992–2018) and its distribution in Spain and Germany but not throughout Europe. In addition to CC1, relationships between non-European and European countries were observed only through ST4, ST17 and ST30. Within Europe, several STs emerged with cross-border circulation, in particular ST16 and ST46 from the major complexes CC2 and CC8. These results constitute a baseline for monitoring the spread of CEM outbreaks. A retrospective analysis of a higher number of strains isolated worldwide between 1977 and the early 2000s would be helpful to obtain an exhaustive picture of the original CEM situation. [ABSTRACT FROM AUTHOR]