Epidemiology, Phylogenetic Divergence, and Differential Pathogenicity of Feline Respiratory Mycoplasma in China

Mycoplasma felis ( M. felis ) is a wall‐less pathogen known to induce respiratory diseases in felines. Current research on respiratory M. felis infections is scant, lacking established typing system and nationwide epidemiological survey. This study investigated the prevalence of M. felis in feline respiratory swabs ( n = 4329) across China from 2022 to 2024. Coinfection profiles involving M. felis , feline herpesvirus (FHV), feline calicivirus (FCV), Chlamydia felis ( C. felis ), and Bordetella bronchiseptica ( Bb ) were assessed in 382 swab samples from cats with respiratory disease. Fifteen representative strains were isolated and characterized to provide insights for disease prevention and vaccine development. Phylogenetic analysis of these isolates revealed two novel clades: the Myco clade (exhibiting classical “fried‐egg” colonies) and the Morella clade (forming “mulberry‐like” microcolonies requiring supplemented media), alongside M. gateae –affiliated strains. Noteworthy strain‐specific metabolic adaptations were observed. Antimicrobial susceptibility testing revealed varying macrolide susceptibility (Morella > gateae > Myco), consistent fluoroquinolone sensitivity, and emerging doxycycline resistance. In vitro virulence was strongly associated with hydrogen peroxide (H 2 O 2 )production, with Morella‐type M. felis ‐8 and Myco‐type M. felis ‐28 showing the highest yields. In vivo challenges in cats validated differential pathogenicity: M. felis ‐28 induced severe respiratory symptoms and lung histopathology (inflammatory infiltration and tissue disruption), while M. felis ‐8 predominantly induced conjunctival injury. Cross‐protection analysis indicated limited antigenic conservation, with high autoreactivity (titer = 1:16) in strains such as M. felis ‐47, but minimal cross‐reactivity (titer ≤ 1:2) among genetically distinct strains. These findings establish a novel diagnostic framework for distinguishing pathogenic clades, facilitating targeted therapeutic interventions and guiding rational vaccine development strategies for M. felis .