Characterisation of Mycoplasma spp. detected in 2020/2021 from respiratory tract samples of horses in France
Résumé
Background: With over 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 replication in vitro. 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 sportive performance. 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 aims of this study are to confirm the prevalence of mycoplasma observed using optimised culture and PCR methods and to characterise the circulating species in France. Study Design: Respiratory samples taken from 1428 French horses were collected and analysed in 2020/2021. Methods: Samples were analysed by culture, rt-PCR and Mycoplasma species were identified by 16S rRNA sequencing or species-specific PCR. Results: 266 horses (18.6%) were found positive by at least one detection method. A majority of M. equirhinis (205/252 rt-PCR positive samples and 104/106 isolated strains) was identified, while M. pulmonis, M. felis and M. lipophilum have been detected only sporadically. Conclusions: Mycoplasmas prevalence in respiratory samples is confirmed and refined. M. equirhinis is the predominant circulating species. The presence of this species will be re-analyzed taking into account the clinical status of the infected horses, using a clinical score, to determine its possible clinical role.