Goerke Christiane, Esser Simone, Kümmel Mirjam, Wolz Christiane
Institut für Medizinische Mikrobiologie und Hygiene, Universitätsklinikum Tübingen, Tübingen, Germany.
Int J Med Microbiol. 2005 Jun;295(2):67-75. doi: 10.1016/j.ijmm.2005.01.004.
The allelic variations of the regulatory operon agr (groups I-IV) and the cap polymorphism (capsular types 5 and 8) were used as a typing scheme for rapid strain designation in Staphylococcus aureus. In combining 10 agr subgroups resolved by restriction fragment length polymorphism (RFLP) analysis with the two cap polymorphisms 12 types could be defined. To assess whether this type designation is informative for the population structure of the species S. aureus, agr and cap types were determined in clonal lineages defined by pulsed-field gel electrophoresis (PFGE) of a collection of 219 isolates. agr groups and cap types were both linked to certain clone complexes. However, little correlation was found between the two polymorphic loci. By PFGE cluster analysis 11 prevalent and 52 sporadic clones were defined. Most of the prevalent clones (9/11) could be discriminated by agr/cap typing. Thus, this technique allows a first subdivision of isolates and an inter-center comparable designation of S. aureus clones preceding a more detailed clonal analysis by PFGE or multi-locus sequence typing (MLST). To get insight into agr diversification, sequence analysis of the variable and conserved part of agr from selected S. aureus clones was performed. Strains of agr-I displayed the highest sequence divergence on the nucleotide and amino acid level, suggesting an early diversification of this group. When analyzing the relationship between the four agr interference groups we could show: (i) one intermediate between agr-I and agr-IV alleles; (ii) agr-IV sequences seem to bridge the agr-I and -III groups and (iii) two cases of horizontal transfer of the variable gene cassette from an agr-I strain to an agr-II strain. Thus, stepwise evolutionary progression and rare events of recombination were evident in the diversification of the agr locus.
调控操纵子agr（I - IV组）的等位基因变异和荚膜多糖多态性（荚膜5型和8型）被用作金黄色葡萄球菌菌株快速分型的方案。通过限制性片段长度多态性（RFLP）分析解析的10个agr亚组与两种荚膜多糖多态性相结合，可定义出12种类型。为评估这种分型方案对金黄色葡萄球菌种群结构是否具有信息价值，对219株菌株集合进行脉冲场凝胶电泳（PFGE）定义的克隆谱系中确定了agr和荚膜多糖类型。agr组和荚膜多糖类型均与某些克隆复合体相关联。然而，在这两个多态性位点之间几乎未发现相关性。通过PFGE聚类分析定义了11个流行克隆和52个散发克隆。大多数流行克隆（9/11）可通过agr/荚膜多糖分型进行区分。因此，这项技术允许在通过PFGE或多位点序列分型（MLST）进行更详细的克隆分析之前，对分离株进行初步细分，并对金黄色葡萄球菌克隆进行中心间可比的分型。为深入了解agr的多样性，对选定的金黄色葡萄球菌克隆的agr可变区和保守区进行了序列分析。agr - I组菌株在核苷酸和氨基酸水平上显示出最高的序列差异，表明该组早期发生了分化。在分析四个agr干扰组之间的关系时，我们可以发现：（i）agr - I和agr - IV等位基因之间存在一个中间类型；（ii）agr - IV序列似乎连接了agr - I和 - III组；（iii）有两例可变基因盒从agr - I菌株水平转移到agr - II菌株的情况。因此，agr基因座的多样化过程中明显存在逐步的进化进程和罕见的重组事件。
