Characterisation of Mycoplasma spp. isolated in 2020 from respiratory tract samples of horses in France

International audienceBackground: With more than 100 species colonizing animal hosts, bacteria of the genus Mycoplasma include important livestock pathogens. They are wall-less and considered as the smallest organisms capable of autonomous growth in vitro. Because their isolation can be laborious, they often lagged behind other bacteria in terms of general knowledge and diagnosis. In horses, three species, namely Mycoplasma (M.) equirhinis, M. pulmonis and M. felis, have been reported from respiratory tract samples, with an unknown pathogenic role but a potential implication on poor-performance [1-2]. In our laboratory, amongst equine respiratory samples submitted routinely for diagnosis, 15% per year turned out to be positive by real-time PCR (rt-PCR) for Mycoplasma spp. but the corresponding species have not been explored yet. Objectives: The aim of this study was to evaluate the prevalence of different species in respiratory clinical samples and characterize their intra species diversity. Study Design: 687 samples (68% tracheal wash, 26% bronchoalveolar lavage and 6% others) collected in 2020 were analysed. Methods: Samples were analysed by culture, rt-PCR and identified by 16S rRNA sequencing. Isolates were subtyped when necessary. Results: To date, 126 samples (18.3%) were found positive by rtPCR and 30 strains have been isolated (still ongoing). A majority of M. equirhinis (42/126 samples and 24/30 strains) was identified, while M. pulmonis and M. felis have been detected only sporadically so far. Main limitation: A gold standard method for Mycoplasma spp. detection and identification in equine samples would be helpful. Conclusions: A Multi Locus Sequence Typing scheme is being developed to analyse the genetic heterogeneity of M. equirhinis isolates. Subtypes will be examined it in the light of their clinical history to have a first insight into the potential pathogenic role of M. equirhinis.1. Allam and Lemcke. doi: 10.1017/s00221724000469082. Antal et al. doi.org/10.1111/j.1439-0450.1988.tb00496.