Department of Clinical Analysis, Pharmaceutical Science Faculty, University of São Paulo, SP, Brazil.
J Dairy Res. 2011 Aug;78(3):373-8. doi: 10.1017/S0022029911000379.
Staphylococcus aureus is one of the most important infectious mastitis causative agents in small ruminants. In order to know the distribution of Staph. aureus strains associated with infectious mastitis in flocks of sheep in the northeast of Brazil and establish whether these clones are related to the strains distributed internationally, this study analysed the genetic diversity of Staph. aureus isolates from cases of clinical and subclinical mastitis in ewes by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). In this research, 135 ewes with mastitis from 31 sheep flocks distributed in 15 districts were examined. Staph. aureus was isolated from sheep milk in 9 (29%) out of 31 herds located in 47% of the districts surveyed. MLST analysis allowed the identification of four STs (ST750, ST1728, ST1729 and ST1730). The last three with their respective novel alleles (glp-220; pta-182 and yqil-180) were recently reported in the Staph. aureus MLST database (http://www.mlst.net). Each novel allele showed only a nucleotide different from those already described. The occurrence of CC133 (ST750 and ST1729) in this study is in agreement with other reports that only a few clones of Staph. aureus seem to be responsible for most cases of mastitis in dairy farms and that some of these clones may have broad geographic distribution. However, the prevalence of CC5 (ST1728 and ST1730)--an important group related to cases of colonization or infection in humans--differs from previous studies by its widespread occurrence and may suggest human contamination followed by selective pressures of the allelic diversifications presented for these STs.
金黄色葡萄球菌是小反刍动物中最重要的传染性乳腺炎病原体之一。为了了解与巴西东北部羊群传染性乳腺炎相关的金黄色葡萄球菌菌株的分布情况，并确定这些克隆株是否与国际分布的菌株有关，本研究通过脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）分析了来自临床和亚临床乳腺炎母羊的金黄色葡萄球菌分离株的遗传多样性。在这项研究中，检查了来自 31 个绵羊群的 135 只患有乳腺炎的母羊，这些绵羊群分布在 15 个区。在位于调查区 47%的 31 个绵羊群中，从 9 个（29%）绵羊群的绵羊乳中分离到了金黄色葡萄球菌。MLST 分析鉴定出了 4 种 ST（ST750、ST1728、ST1729 和 ST1730）。后三种分别带有其各自的新等位基因（glp-220；pta-182 和 yqil-180），最近在金黄色葡萄球菌 MLST 数据库（http://www.mlst.net）中被报道。每个新等位基因与已描述的等位基因仅相差一个核苷酸。本研究中 CC133（ST750 和 ST1729）的出现与其他报道一致，即只有少数金黄色葡萄球菌克隆似乎是导致奶牛场乳腺炎大多数病例的原因，其中一些克隆可能具有广泛的地理分布。然而，CC5（ST1728 和 ST1730）的流行率（一个与人类定植或感染相关的重要群体）与其广泛的流行率不同，这可能表明存在人类污染，随后是这些 ST 所呈现的等位基因多样化的选择性压力。
