Strains used in this study.

(i) xylose inducible, WT = wild-type isolate.
All strains were tested for hemolysis (sign for α-toxin production) on blood agar plates after 24 h and results are listed semi-quantitatively in four categories: -, no hemolysis; +/−, borderline; +, ++, efficient hemolysis. PVL production of different strains was determined by Western blot analysis of bacterial culture supernatants as described and shown in figures S1B, S1C. The results are listed semi-quantitatively in five categories: -, no PVL production; +/−, borderline; +, low; ++, +++, high amounts of PVL production.

(i) 木糖诱导型，WT即野生型分离菌株（wild-type isolate）。所有菌株均于血琼脂平板上培养24小时后检测溶血反应（α毒素产生的标志），结果以半定量方式分为四个等级：-代表无溶血；+/−代表边界弱阳性；+、++代表高效溶血。不同菌株的潘顿-瓦伦丁杀白细胞素（PVL）产生情况通过细菌培养上清液的蛋白质印迹法（Western blot）分析检测，具体方法如前文所述，结果如图S1B、S1C所示。结果以半定量方式分为五个等级：-代表无PVL产生；+/−代表边界弱阳性；+代表低水平产生；++、+++代表PVL高水平产生。