Mycoplasma bovis isolates from Chinese dairy farms: Analysis of genomic features, antimicrobial resistance, and virulence-associated structural differences.

Abstract

Mycoplasma bovis (M. bovis) is an emerging major bovine pathogen, causing economic losses worldwide in the dairy and beef industry. In this study, whole-genome sequencing was performed on 47 representative isolates collected from 11 provinces in China between 2018 and 2023, and the data were compared with 86 global reference genomes. Core SNP phylogeny and core genome multilocus sequence typing (cgMLST) showed that Chinese isolates were mainly attributed to type I spectrum, ST-52 was the dominant type (87.5 %), with high overall homology and geographical clustering. Annotation of virulence factors identified six categories of functional genes, while Chinese isolates displayed varying degrees of deletions within the vsp family and the adhesion-immune modulation region (Mbov_0723-Mbov_0735). Functional validation using representative strains-PZJS01 (complete), PZNX02 (partially undetected), and PZHLJ02 (large-fragment undetected)-demonstrated that PZJS01, which harbors an intact pathogenicity island, exhibited stronger invasiveness and significantly induced host cell apoptosis (∼28 %). These findings indicate that this structural region may play a critical role in the pathogenic process. Antimicrobial susceptibility testing revealed that Chinese isolates were generally resistant to erythromycin (97.9 %) and tylosin (59.6 %), and all strains were non-susceptible to oxytetracycline, showing a pattern of multidrug resistance. In contrast, doxycycline and tiamulin exhibited favorable in vitro activity based on MIC testing. This study systematically elucidates the clonal dissemination patterns, virulence evolution, and antimicrobial resistance risks of M. bovis in China, providing scientific evidence for the development of control strategies and vaccine design.