The alert for emergence of pig-associated MRSA ST 398 in multi-regions China

Livestock-associated Methicillin-resistant Staphylococcus aureus (LA-MRSA) lineage ST398 presents a notable public health risk through its transmission from pigs to humans. This study characterizes phenotypic and genomic features of pig-associated MRSA ST398 isolates in China. Through surveillance (2015-2021) of 296 S. aureus isolates from major pork-producing regions, we identified 14 MRSA isolates in Zhejiang, Fujian, Guangdong, and Shanxi provinces, with 12 (85.7 %) belonging to the ST398 lineage. These isolates displayed two genetic profiles: t011-SCCmec V (10/12) and t571-SCCmec XII (2/12), and exhibited multidrug resistance to penicillin, oxacillin, cefoxitin, erythromycin, and clindamycin. Phylogenetic analysis revealed three critical findings: (1) clonal dissemination within Shanxi (0-48 SNPs), (2) potential interprovincial spread between geographically distant regions (Shanxi-Qinghai, 17-44 SNPs), and (3) concerning genetic linkage (70 SNPs) between a Zhejiang isolate and European ST398 isolate. These results underscore the urgent need for integrated pork supply chain surveillance strategies to monitor this emerging zoonotic pathogen.