The aim of this study was to investigate antimicrobial resistance and population structure of bovine mastitis-associated Staphylococcus aureus isolates, and compare them to human isolates obtained from Western Australian hospitals and overseas strains to determine relatedness to human isolates from a zoonotic or reverse zoonotic aspect. Antimicrobial susceptibility testing was performed on 202 S. aureus isolates of which 166 isolates underwent whole genome sequencing. Only resistance to penicillin (12.4%) and erythromycin (0.5%) was identified and of note, no resistance was demonstrated to oxacillin. Genomic characterisation identified 14 multilocus sequence types (STs), with most isolates belonging to clonal complexes 97, 705, and 1. Four distinct clades based on virulence gene composition were identified. The four clades were predominantly ST based, consisting of ST352, ST97, ST81/ST1, and ST705. Core genome comparison of the bovine and human S. aureus isolates demonstrated defined clustering by ST, with the Australian bovine S. aureus isolates clustering together according to their ST separately from human isolates. In addition, a bovine specific cluster comprising Australian ST151 and ST705 isolates, and ST151 isolates from Irish dairy cattle was clearly delineated. Examination of a detailed ST352 phylogeny provided evidence for geographical clustering of Australian strains into a distinct grouping separate from international strains. This study has identified Australian S. aureus isolates have limited genetic diversity and are genetically distinct from human and international bovine S. aureus isolates. Current first line therapies for bovine mastitis in Australian dairy cattle remain appropriate.

这项研究的目的是调查与牛乳腺炎相关的金黄色葡萄球菌分离株的抗药性和种群结构，并将它们与从西澳大利亚医院和海外菌株获得的人分离株进行比较，以从人畜共患或反人畜共患方面确定与人分离株的相关性。对202金黄色葡萄球菌进行了药敏试验其中的166个分离株进行了全基因组测序。仅鉴定出对青霉素（12.4％）和红霉素（0.5％）的耐药性，值得注意的是，未显示出对奥沙西林的耐药性。基因组鉴定确定了14种多位点序列类型（ST），其中大多数分离物属于克隆复合体97、705和1。根据毒力基因组成鉴定出四个不同的进化枝。这四个分支主要基于ST，包括ST352，ST97，ST81 / ST1和ST705。牛和人金黄色葡萄球菌分离物的核心基因组比较证明了ST与澳大利亚牛金黄色葡萄球菌的明确聚类分离株根据其ST与人类分离株分开聚集在一起。另外，清楚地描绘了包括澳大利亚ST151和ST705分离株以及来自爱尔兰奶牛的ST151分离株的牛特异性簇。对详细ST352系统发育的研究为澳大利亚菌株在地理上聚类为与国际菌株分离的不同分组提供了证据。这项研究已经确定了澳大利亚金黄色葡萄球菌分离株具有有限的遗传多样性，并且在遗传上不同于人和国际牛金黄色葡萄球菌分离株。澳大利亚奶牛目前对牛乳腺炎的一线疗法仍然合适。