浙江省14型血清型猪链球菌基因组比较与时空追溯OA

This study was aimed at characterizing the genomic features,population structure,and evolutionary origins of the first human-derived Streptococcus suis serotype 14(SS14)isolate identified in Zhejiang Province,China,by comparative analysis of 194 publicly available SS14 genomes.Whole-genome sequencing(WGS)and antimicrobial susceptibility testing(16 antibiotics,microdi-lution method)were performed on the Zhejiang SS14 strain.Population structure was analyzed with multi-locus sequence typing(MLST)and minimum core genome(MCG)typing across 195 SS14 genomes.Core single nucleotide polymorphism(SNP)-based phy-logenetic trees were constructed with IQ-TREE,and virulence-associated genes(VAGs),antimicrobial resistance genes(ARGs),mo-bile genetic elements(MGEs),and prophages were identified with established bioinformatics tools.Bayesian phylogenetic analysis and transmission timeline inference were conducted with Snippy and BEAST.The Zhejiang SS14 strain exhibited full susceptibility to all tested antimicrobial agents.MLST and MCG analysis revealed four dominant global lineages:ST7/CC1/MCG1(exclusive to China),ST1/CC1/MCG1(globally distributed),ST28/CC28/MCG4,and ST105/CC1/MCG1.The Zhejiang strain clustered within the ST1/CC1/MCG1 lineage.Phylogenetic analysis grouped all 195 strains into six clades,and Chinese isolates were dispersed across four clades.ST7/CC1/MCG1 formed the largest epidemic clade and potentially originated from ST7-type SS2 via capsular gene replacement.A total of 28 ARGs were detected,primarily vanY,patA,patB,tet(O),ermB,and ANT(6)-Ia(which was restricted to Chinese strains).Nine-teen VAGs were identified,including ef,mrp,sly,cbpD,rmlA,zmpC,and hylA.Notable diversity in MGEs and prophage content was ob-served among lineages.Bayesian analysis suggested three separate introductions of SS14 into China:one domestic and two imported from Europe via North America(2012 and 2016).Four major SS14 epidemic populations circulate globally,and ST7/CC1/MCG1 are found predominantly in China and are likely to be derived from SS2.The Zhejiang SS14 strain is closely related to European isolates and was probably introduced into China through transcontinental transmission in 2016.