National Veterinary Institute, SE-751 89 Uppsala, Sweden.
J Dairy Sci. 2010 Apr;93(4):1534-8. doi: 10.3168/jds.2009-2544.
Staphylococcus aureus is an important udder pathogen often associated with subclinical mastitis in dairy cows. Identification of Staph. aureus-positive udder quarters and cows is an important part of control programs to reduce spread of Staph. aureus within and between dairy herds. Therefore, accurate and easy-to-perform culturing methods of Staph. aureus in milk are needed. In the present study, 8 methods for isolation of Staph. aureus in bovine milk samples were investigated. The methods involved different culturing volumes, enrichment, incubation, and freezing processes as well as sedimentation and use of the Mastistrip cassette (SVA, Uppsala, Sweden). Three different sets of milk samples were collected, and 6, 5, and 4 methods were used in each subset of samples. Our results indicate an increased probability of detecting Staph. aureus in milk samples when a simple incubation step (37 degrees C for 18 h) without additives was included before culturing. Using this incubation method, the number of Staph. aureus-positive udder quarters and cows increased by 50 and 29%, respectively, compared with using the standard method of direct culturing of 10 microL of milk. The improved method may be especially useful for detection of low concentrations of Staph. aureus in milk; for example, when screening herds for Staph. aureus.
金黄色葡萄球菌是一种重要的乳房病原体，常与奶牛亚临床乳腺炎有关。鉴定金黄色葡萄球菌阳性乳房部位和奶牛是减少金黄色葡萄球菌在奶牛群内和群间传播的控制计划的重要组成部分。因此，需要准确且易于执行的牛奶中金黄色葡萄球菌培养方法。本研究调查了 8 种从牛乳样本中分离金黄色葡萄球菌的方法。这些方法涉及不同的培养体积、富集、孵育和冷冻过程以及 Mastistrip 盒（SVA，乌普萨拉，瑞典）的沉淀和使用。收集了三组不同的牛奶样本，在每组样本中使用了 6、5 和 4 种方法。我们的结果表明，在培养前加入简单的孵育步骤（37°C 孵育 18 小时），可提高牛奶样本中金黄色葡萄球菌的检出概率。与直接培养 10 μL 牛奶的标准方法相比，使用这种孵育方法，金黄色葡萄球菌阳性乳房部位和奶牛的数量分别增加了 50%和 29%。该改进方法可能特别有助于检测牛奶中低浓度的金黄色葡萄球菌；例如，在对金黄色葡萄球菌进行群筛查时。
