Department of Paraclinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, 0454 Oslo, Norway.
M-team and Mastitis and Milk Quality Research Unit, Department of Reproduction, Obstetrics, and Herd Health, Faculty of Veterinary Medicine, Ghent University (UGent), 9820 Merelbeke, Belgium.
J Dairy Sci. 2021 Sep;104(9):10250-10267. doi: 10.3168/jds.2020-19988. Epub 2021 Apr 30.
Mastitis is a prevalent disease in dairy cattle, and staphylococci are among the most common causative pathogens. Staphylococci can express resistance to a range of antimicrobials, of which methicillin resistance is of particular public health concern. Additionally, Staphylococcus aureus carries a variety of virulence factors, although less is understood about the virulence of non-aureus staphylococci (NAS). The aim of our study was to identify and characterize 3 collections of staphylococcal isolates from bovine milk samples regarding antimicrobial resistance, with emphasis on methicillin resistance, and their carriage of virulence genes typically displayed by Staph. aureus. A total of 272 staphylococcal isolates collected in Norway and Belgium in 2016 were included, distributed as follows: group 1, Norway, 100 isolates; group 2, Flanders, Belgium, 64 isolates; group 3, Wallonia, Belgium, 108 isolates. Species identification was performed by use of MALDI-TOF mass spectrometry. Phenotypic resistance was determined via disk diffusion, and PCR was used for detection of methicillin resistance genes, mecA and mecC, and virulence genes. Antimicrobial resistance was common in Staphylococcus epidermidis and Staphylococcus haemolyticus from all different groups, with resistance to trimethoprim-sulfonamide frequently occurring in Staph. epidermidis and Staph. haemolyticus as well as in Staph. aureus. Resistance to penicillin was most frequently observed in group 1. Ten Belgian isolates (1 from group 2, 9 from group 3) carried the methicillin resistance determinant mecA: 5 Staph. aureus from 2 different farms and 5 NAS from 3 different farms. Almost all Staph. aureus isolates were positive for at least 3 of the screened virulence genes, whereas, in total, only 8 NAS isolates harbored any of the same genes. Our study contributes to the continuous need for knowledge regarding staphylococci from food-producing animals as a basis for better understanding of occurrence of resistance and virulence traits in these bacteria.
乳腺炎是奶牛中常见的疾病，葡萄球菌是最常见的病原体之一。葡萄球菌可以表达对多种抗生素的耐药性，其中耐甲氧西林的耐药性尤其引起公众健康的关注。此外，金黄色葡萄球菌携带多种毒力因子，尽管对非金黄色葡萄球菌（NAS）的毒力了解较少。我们的研究旨在鉴定和描述从挪威和比利时的牛乳样本中分离的 3 组葡萄球菌，重点是耐甲氧西林的耐药性，以及它们携带的金黄色葡萄球菌通常表现出的毒力基因。共包括 2016 年在挪威和比利时收集的 272 株葡萄球菌分离株，分布如下：第 1 组，挪威，100 株；第 2 组，比利时佛兰德，64 株；第 3 组，比利时瓦隆，108 株。使用 MALDI-TOF 质谱法进行种属鉴定。通过纸片扩散法测定表型耐药性，PCR 用于检测耐甲氧西林基因 mecA 和 mecC 以及毒力基因。所有不同组别的表皮葡萄球菌和溶血葡萄球菌均普遍存在抗生素耐药性，表皮葡萄球菌和溶血葡萄球菌以及金黄色葡萄球菌中经常出现对甲氧苄啶-磺胺甲恶唑的耐药性。第 1 组中最常观察到对青霉素的耐药性。10 株来自比利时的分离株（2 株来自第 2 组，9 株来自第 3 组）携带耐甲氧西林决定子 mecA：来自 2 个不同农场的 5 株金黄色葡萄球菌和来自 3 个不同农场的 5 株 NAS。几乎所有金黄色葡萄球菌分离株均至少对 3 个筛选的毒力基因呈阳性，而总共只有 8 株 NAS 分离株携带任何相同的基因。我们的研究有助于不断了解食品生产动物中的葡萄球菌，为更好地了解这些细菌的耐药性和毒力特征提供基础。
