Instituto de Microbiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
Int J Med Microbiol. 2013 Dec;303(8):505-13. doi: 10.1016/j.ijmm.2013.07.004. Epub 2013 Jul 18.
The emergence of highly virulent and successful Streptococcus pyogenes (group A streptococci - GAS) clones has been attributed to the exchange of virulence factors by lateral gene transfer mechanisms, which strongly contribute to genomic diversity. We characterized a collection of 191 GAS isolates recovered from normally sterile sites in Portugal during 2006-2009 and compared them to invasive isolates obtained during 2000-2005. Antimicrobial resistance rates did not change significantly between the two periods and were generally low. In 2006-2009, emm1, emm89, emm3, and emm6 represented 60% of the isolates. The chromosomally encoded superantigen (SAg) genes speG and smeZ were present in the majority (>90%) of the isolates, while speJ was found in only 45%. The phage encoded SAgs varied greatly in prevalence (2-53%). The distribution of emm types, pulsed-field gel electrophoresis profiling (PFGE) clusters, and SAg profiles changed significantly between the periods, although there were no statistically supported changes in the prevalence of individual types. While the macrolide susceptible clone emm1-T1-ST28 remained dominant (28%), there was a significant decrease in clonal diversity as indicated by both PFGE profiling and emm typing. This was accompanied by intra-clonal divergence of SAg profiles, which was statistically confirmed for isolates representing emm1, emm28, and emm44. This diversification was associated with the loss and acquisition of SAg genes, carried by phages and of chromosomal origin. These data suggest an ongoing genomic diversification of GAS invasive isolates in Portugal that may contribute to the persistence of clones with improved fitness or virulence.
产毒性强且具高度侵袭性的化脓性链球菌（A 群链球菌-GAS）克隆株的出现归因于毒力因子通过基因水平转移机制的交换，这强烈促成了基因组的多样性。我们对 2006 年至 2009 年期间从葡萄牙无菌部位采集的 191 株 GAS 分离株进行了特征描述，并与 2000 年至 2005 年期间获得的侵袭性分离株进行了比较。两个时期之间的抗生素耐药率没有显著变化，且通常较低。2006 年至 2009 年，emm1、emm89、emm3 和 emm6 占分离株的 60%。大多数（>90%）分离株存在染色体编码的超抗原（SAg）基因 speG 和 smeZ，而 speJ 仅存在于 45%的分离株中。噬菌体编码的 SAg 流行率差异很大（2-53%）。emm 型、脉冲场凝胶电泳图谱（PFGE）聚类和 SAg 图谱的分布在两个时期均有显著变化，尽管个别类型的流行率没有统计学支持的变化。虽然大环内酯类敏感克隆 emm1-T1-ST28 仍然占主导地位（28%），但 PFGE 图谱和 emm 分型均表明克隆多样性显著下降。这伴随着 SAg 图谱的种内分化，这在代表 emm1、emm28 和 emm44 的分离株中得到了统计学确认。这种多样化与噬菌体和染色体来源携带的 SAg 基因的丢失和获得有关。这些数据表明，葡萄牙侵袭性 GAS 分离株的基因组多样性正在不断发生，这可能有助于具有改善适应性或毒力的克隆株的持续存在。
