1株马乳源PVL+ST22型金黄色葡萄球菌致病性分析

Pathogenicity Analysis of a PVL+ST22 Staphylococcus aureus Isolated from Equine Raw Milk

国内鲜有马乳源PVL+ST22型金黄色葡萄球菌(Staphylococcus aureus)相关报道,本研究对1株新疆马乳源PVL+ST22型金黄色葡萄球菌的致病性进行评估,以期为马乳源金黄色葡萄球菌的相关研究提供基础数据。使用选择性培养基从新疆健康马乳中分离金黄色葡萄球菌,然后通过生化鉴定和分子鉴定方法对金黄色葡萄球菌进行鉴定。对所获得的金黄色葡萄球菌进行多位点序列分型(multilocus sequence typing,MLST)、spa分型、药物敏感性检测、生物被膜形成能力、溶血活性、毒力基因检测、小鼠皮肤脓肿和致病性试验。再对分离株进行小鼠细胞的黏附、侵袭和胞内增殖试验,以评估其致病性。结果显示,从马乳中分离得到1株PVL+ST22型金黄色葡萄球菌(1/65,1.5%),spa分型为t304。仅对青霉素耐药,无生物被膜形成能力,但携带9种毒力基因(sec、seg、seh、tsst-1、hla、hlb、clfA、clfB和cna),并且具有溶血活性。小鼠皮肤脓肿和致病性试验表明,其可导致小鼠形成皮肤脓肿,并且在高剂量感染时可导致小鼠死亡。ST22型金黄色葡萄球菌可在小鼠巨噬细胞中黏附(4.26%)、侵袭(6.45%)和胞内增殖,并可造成细胞凋亡。综上,马乳源PVL+ST22型金黄色葡萄球菌具有较强的致病力,可能在宿主致病和公共卫生安全等方面存在隐患。

There are few reports on PVL+ST22 Staphylococcus aureus(S.aureus)isolated from equine milk in China.This study was conducted to evaluate the pathogenicity of an S.aureus(PVL+ST22)isolated from equine milk in Xinjiang,hoping to provide basic data for the study of S.aureus from equine milk in China.S.aureus taphylococci were isolated from apparently healthy equine milk in Xinjiang using the selective medium and then identified by biochemical and molecular identification methods for S.aureus.The obtained S.aureus were subjected to multilocus sequence typing(MLST),spa typing,antimicrobial susceptibility testing,and biofilm-forming ability,hemolytic activity,virulence gene detection,along with mouse skin abscess and pathogenicity assay.The isolated strain was then subjected to mouse macrophage adhesion,invasion,and intracellular proliferation assays to assess their pathogenicity.The results indicated that a PVL+ST22 S.aureus(1/65,1.5%)strain was isolated from equine milk,with spa typing t304.It was resistant to penicillin only,had no biofilm-forming ability,but carried 9 virulence genes(sec,seg,seh,tsst-1,hla,hlb,clfA,clfB,and cna)and has hemolytic activity.Mouse skin abscess and pathogenicity tests also showed that it caused skin abscess formation and death in mice at high doses of infection.ST22 S.aureus has adhered(4.26%),invaded(6.45%),and proliferated intracellularly in mouse macrophages and caused apoptosis tic cell death.In conclusion,the PVL+ST22 S.aureus isolated from equine milk is highly pathogenic and may pose potential risks in terms of host pathogenicity and public health safety.