Proteomic and genomic characterisation of Mycoplasma felis isolated from cats, wild Felinae and horses

Mycoplasma (M.) felis is a globally distributed, opportunistic pathogen primarily associated with infections in domestic cats. It has been implicated in various clinical manifestations including conjunctivitis, respiratory tract disease, arthritis, and serosal inflammation. Although commonly considered a commensal organism of feline mucosal surfaces, accumulating evidence highlights its pathogenic potential under certain host or environmental conditions. This thesis investigated the relatedness of M. felis isolates obtained from domestic cats, wild Felinae, and horses. A total of 49 M. felis isolates including two different colony morphotypes (opaque, lucent) of seven isolates, and the type strain of M. felis (COT) were analyzed using genomic and proteomic typing methods. A newly established core genome multilocus sequence typing (cgMLST) scheme was employed to construct phylogenetic relationships among M. felis strains. For the proteomic characterization matrix assisted laser desorption ionization – time of flight (MALDI-ToF) mass spectrometry was used to generate protein mass spectra from which a dendrogram reflecting spectral distances was created. The newly developed cgMLST scheme encompassing 454 target genes revealed high diversity of the studied M. felis strains separated into two major clusters, with some evidence of hostspecific clustering of equine isolates. Interestingly, the colony variants of M. felis isolates (opaque or lucent) each clustered together or even showed an identical cgMLST profile, suggesting that the colony morphotype is driven by genes that are not part of the core genome. In contrast, although the MALDI-TOF mass spectrometry also grouped the isolates into two main clusters, no correlations were found between clustering and epidemiologic data or phylogenetic grouping based on cgMLST. Overall, the newly established cgMLST appears to be a suitable method for investigating the epidemiology of M. felis infection and gaining insights into the population structure of this underestimated pathogen.