Merz Axel, Stephan Roger, Johler Sophia
Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich Zurich, Switzerland.
Front Microbiol. 2016 Mar 14;7:319. doi: 10.3389/fmicb.2016.00319. eCollection 2016.
Dairy goat and sheep farms suffer severe economic losses due to intramammary infections, with Staphylococcus aureus representing the main cause of clinical mastitis in small ruminants. In addition, S. aureus contamination of goat and sheep milk may cause staphylococcal food poisoning, as many traditional caprine and ovine milk products are not subjected to pasteurization. Data on virulence and antimicrobial resistance genes, as well as on the clonality of S. aureus detected in goat and sheep milk is scarce. Therefore, it was the aim of this study to determine (i) spa types and clonal complexes (CC) and (ii) virulence and resistance gene profiles of S. aureus isolated from goat and sheep milk. A total of 162 milk samples from sheep and goats presenting signs of an intramammary infection and 104 bulk milk samples were collected. While low prevalence rates of S. aureus was detected on single animal level, 46% of the bulk tank milk samples from small ruminants were positive for S. aureus. All isolates were spa typed and CC and virulence and resistance gene patterns were determined using a DNA microarray. Data from 49 S. aureus isolates was included in the statistical analysis and the construction of a SplitsTree. The analyzed isolates could be assigned to eleven CC, with the large majority of goat and sheep isolates being assigned to CC130 and CC133. The findings of this study suggest that S. aureus shows pronounced adaptation to small ruminants in general, but not to sheep or goats in particular. Although some common characteristics among S. aureus from caprine, ovine, and bovine milk samples were observed, S. aureus from small ruminants seem to form a distinct population. As 67% of the detected S. aureus strains exhibited at least one enterotoxin gene, many caprine, or ovine raw milk products may be contaminated with low levels of enterotoxigenic S. aureus, stressing the importance of strict maintenance of the cold chain.
奶山羊和绵羊养殖场因乳房内感染遭受严重经济损失，金黄色葡萄球菌是小反刍动物临床乳腺炎的主要病因。此外，山羊奶和绵羊奶被金黄色葡萄球菌污染可能导致葡萄球菌食物中毒，因为许多传统的山羊奶和绵羊奶制品未经过巴氏杀菌。关于山羊奶和绵羊奶中检测到的金黄色葡萄球菌的毒力、抗菌耐药基因以及克隆性的数据很少。因此，本研究的目的是确定：（i）spa分型和克隆复合体（CC），以及（ii）从山羊奶和绵羊奶中分离出的金黄色葡萄球菌的毒力和耐药基因谱。共收集了162份有乳房内感染迹象的绵羊和山羊奶样以及104份混合奶样。虽然在单只动物水平上检测到金黄色葡萄球菌的患病率较低，但46%的小反刍动物混合奶罐样品金黄色葡萄球菌呈阳性。对所有分离株进行spa分型，并使用DNA微阵列确定CC以及毒力和耐药基因模式。49株金黄色葡萄球菌分离株的数据纳入统计分析并构建分裂树。分析的分离株可分为11个CC，绝大多数山羊和绵羊分离株属于CC130和CC133。本研究结果表明，金黄色葡萄球菌总体上对小反刍动物有明显适应性，但并非特别针对绵羊或山羊。虽然在山羊奶、绵羊奶和牛奶样品中的金黄色葡萄球菌之间观察到一些共同特征，但小反刍动物来源的金黄色葡萄球菌似乎形成一个独特的群体。由于检测到的金黄色葡萄球菌菌株中有67%至少含有一个肠毒素基因，许多山羊奶或绵羊奶生鲜制品可能被低水平的产肠毒素金黄色葡萄球菌污染，这凸显了严格维持冷链的重要性。
