Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, California, United States of America.
Department of Animal and Veterinary Sciences, University of Vermont, Burlington, Vermont, United States of America.
PLoS One. 2021 Mar 15;16(3):e0243688. doi: 10.1371/journal.pone.0243688. eCollection 2021.
Staphylococcus chromogenes is a common skin commensal in cattle and has been identified as a frequent cause of bovine mastitis and intramammary infections. We have developed a seven locus Multilocus Sequence Typing (MLST) scheme for typing S. chromogenes. Sequence-based typing systems, such as MLST, have application in studies of genetic diversity, population structure, and epidemiology, including studies of strain variation as a factor in pathogenicity or host adaptation. The S. chromogenes scheme was tested on 120 isolates collected from three geographic locations, Vermont and Washington State in the United States and Belgium. A total of 46 sequence types (STs) were identified with most of the STs being location specific. The utility of the typing scheme is indicated by a discrimination power of 95.6% for all isolates and greater than 90% for isolates from each of the three locations. Phylogenetic analysis placed 39 of the 46 STs into single core group consistent with a common genetic lineage; the STs in this group differ by less than 0.5% at the nucleotide sequence level. Most of the diversification in this lineage group can be attributed to mutation; recombination plays a limited role. This lineage group includes two clusters of single nucleotide variants in starburst configurations indicative of recent clonal expansion; nearly 50% of the isolates sampled in this study are in these two clusters. The remaining seven STs were set apart from the core group by having alleles with highly variable sequences at one or more loci. Recombination had a higher impact than mutation in the diversification of these outlier STs. Alleles with hypervariable sequences were detected at five of the seven loci used in the MLST scheme; the average sequence distances between the hypervariable alleles and the common core alleles ranged from 12 to 34 nucleotides. The extent of these sequence differences suggests the hypervariable alleles may be remnants of an ancestral genotype.
染色葡萄球菌是牛皮肤上的一种常见共生菌，已被确定为牛乳腺炎和乳腺内感染的常见原因。我们已经开发了一种用于葡萄球菌属的 7 个基因座多位点序列分型（MLST）方案。基于序列的分型系统，如 MLST，可应用于遗传多样性、种群结构和流行病学研究，包括作为致病性或宿主适应性因素的菌株变异研究。该葡萄球菌属方案在从三个地理位置（美国的佛蒙特州和华盛顿州以及比利时）采集的 120 个分离株上进行了测试。共鉴定出 46 个序列型（ST），其中大多数 ST 是特定于位置的。该分型方案的实用性体现在所有分离株的区分力为 95.6%，并且每个地理位置的分离株均大于 90%。系统发育分析将 46 个 ST 中的 39 个归入单个核心群，这与共同的遗传谱系一致；该组中的 ST 在核苷酸序列水平上差异小于 0.5%。该谱系群中的大多数多样化可归因于突变；重组的作用有限。该谱系群包括两个星爆构型的单核苷酸变异簇，表明最近的克隆扩张；本研究中采样的近 50%的分离株都在这两个簇中。其余的七个 ST 与核心群分开，因为一个或多个基因座的等位基因具有高度可变的序列。重组对这些异常 ST 的多样化的影响大于突变。在 MLST 方案中使用的七个基因座中的五个基因座检测到高变序列的等位基因；高变等位基因与常见核心等位基因之间的平均序列差异范围为 12 至 34 个核苷酸。这些序列差异的程度表明高变等位基因可能是祖先基因型的残余。
