Staphylococcus aureus causes persistent clinical and subclinical bovine intramammary infections (IMI) worldwide. However, there is a lack of comprehensive information regarding genetic diversity, the presence of antimicrobial resistance (AMR), and virulence genes for S. aureus in bovine milk in Canada. Here, we performed whole-genome sequencing (WGS) of 119 Canadian bovine milk S. aureus isolates and determined they belonged to 8 sequence types (ST151, ST352, ST351, ST2187, ST2270, ST126, ST133, and ST8), 5 clonal complexes (CC151, CC97, CC126, CC133, and CC8), and 18 distinct Spa types. Pan-, core, and accessory genomes were composed of 6,340, 1,279, and 2,431 genes, respectively. Based on phenotypic screening for AMR, resistance was common against beta-lactams (19% of isolates) and sulfonamides (7% of isolates), whereas resistance against pirlimycin, tetracycline, ceftiofur, and erythromycin and to the combination of penicillin and novobiocin was uncommon (3, 3, 3, 2, and 2% of all isolates, respectively). We also determined distributions of 191 virulence factors (VFs) in 119 S. aureus isolates after classifying them into 5 functional categories (adherence [n = 28], exoenzymes [n = 21], immune evasion [n = 20], iron metabolism [n = 29], and toxins [n = 93]). Additionally, we calculated the pathogenic potential of distinct CCs and STs and determined that CC151 (ST151 and ST351) had the highest pathogenic potential (calculated by subtracting core-VFs from total VFs), followed by CC97 (ST352 and ST2187) and CC126 (ST126 and ST2270), potentially linked to their higher prevalence in bovine IMI worldwide. However, there was no statistically significant link between the presence of VF genes and mastitis.

中文翻译：

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牛奶中牛金黄色葡萄球菌分离物的基因组分析，以阐明多样性并确定抗菌和毒力基因的分布及其与乳腺炎的关系。

金黄色葡萄球菌在全世界引起持续的临床和亚临床牛乳内感染（IMI）。但是，在加拿大，关于遗传多样性，抗菌素耐药性（AMR）和金黄色葡萄球菌的毒力基因的存在，缺乏全面的信息。在这里，我们对119种加拿大牛乳金黄色葡萄球菌进行了全基因组测序（WGS）分离物并确定它们属于8种序列类型（ST151，ST352，ST351，ST2187，ST2270，ST126，ST133和ST8），5种克隆复合体（CC151，CC97，CC126，CC133和CC8）和18种不同的Spa类型。泛基因组，核心基因组和辅助基因组分别由6,340、1,279和2,431个基因组成。根据对AMR的表型筛选，对β-内酰胺类（占分离物的19％）和磺酰胺类药物（占分离物的7％）的抵抗力很普遍，而对Pirlimycin，tetracycline，ceftiofur和erythromycin以及对青霉素和novobiocin的联合耐药性则不常见。 （分别占所有分离株的3％，3％，3％，2％和2％）。在将119个金黄色葡萄球菌分离株分为5个功能类别后，我们还确定了191个毒力因子（VF）的分布（粘附性[ n= 28]，外酶[ n = 21]，逃避免疫[ n = 20]，铁代谢[ n = 29]和毒素[ n = 93]）。此外，我们计算了不同CC和ST的致病性，并确定CC151（ST151和ST351）具有最高致病性（通过从总VF中减去核心VF计算），其次是CC97（ST352和ST2187）和CC126（ST126）和ST2270），可能与其在全球牛IMI中的较高患病率有关。但是，VF基因的存在与乳腺炎之间没有统计学上的显着联系。