Exploring the pangenome of Mycoplasma hyorhinis in search of potential virulence markers.

Mycoplasma hyorhinis (homotypic synonym of Mesomycoplasma hyorhinis) is a pathobiont from the upper respiratory tract of pigs. Under unclear circumstances, it can disseminate systemically and cause disease. Although some studies have reported different infectious capabilities among strains, no factors have been directly linked to virulence. This study aimed to analyze the core and accessory genes of all available M. hyorhinis strains (pangenome) to identify potential virulence markers. We characterized the pangenome of 110 strains, including isolates from healthy (nasal cavity) and diseased (systemic organs, nasal cavity or lung) animals. Comparative analyses were performed according to the clinical background. Although most putative virulence genes were shared, we identified several genes absent in most health-associated strains related to DNA-processing mechanisms, including hsdM-hsdR restriction-modification system and various helicases. Furthermore, the particular analysis of variable lipoprotein (vlp) genes revealed a similar presence in all strains but higher number of repeats in region III of vlpF in strains isolated from systemic lesions. Genome-scale metabolic models were used to infer the metabolic capabilities of the strains, showing highly conserved predicted reactomes, including growth capabilities and auxotrophies. In conclusion, although all strains may carry genes enabling disease, nasal strains from healthy animals lacked some DNA-processing genes and showed distinct vlp patterns. Additional genomes, especially from strains isolated from healthy animals, would be needed to confirm these findings.