CHU de Rennes, Service de Bactériologie-Hygiène Hospitalière, Rennes, France.
Inserm, CIC 1414, Rennes, France.
PLoS One. 2020 Dec 17;15(12):e0244063. doi: 10.1371/journal.pone.0244063. eCollection 2020.
Streptococcus pyogenes or group A Streptococcus (GAS) causes diseases ranging from uncomplicated pharyngitis to life-threatening infections. It has complex epidemiology driven by the diversity, the temporal and geographical fluctuations of the circulating strains. Despite the global burden of GAS diseases, there is currently no available vaccination strategy against GAS infections. This study, based on a longitudinal population survey, aimed to understand the dynamic of GAS emm types and to give leads to better recognition of underlying mechanisms for the emergence of successful clones. From 2009 to 2017, we conducted a systematic culture-based diagnosis of GAS infections in a French Brittany population with a prospective recovery of clinical data. The epidemiological analysis was performed using emm typing combined with the structural and functional cluster-typing system for all the recovered strains. Risk factors for the invasiveness, identified by univariate analysis, were computed in a multiple logistic regression analysis, and the only independent risk factor remaining in the model was the age (OR for the entire range [CI95%] = 6.35 [3.63, 11.10]; p<0.0001). Among the 61 different emm types identified, the most prevalent were emm28 (16%), emm89 (15%), emm1 (14%), and emm4 (8%), which accounted for more than 50% of circulating strains. During the study period, five genotypes identified as emm44, 66, 75, 83, 87 emerged successively and belonged to clusters D4, E2, E3, and E6 that were different from those gathering "Prevalent" emm types (clusters A-C3 to 5, E1 and E4). We previously reported significant genetic modifications for emm44, 66, 83 and 75 types resulting possibly from a short adaptive evolution. Herein we additionally observed that the emergence of a new genotype could occur in a susceptible population having specific risk factors or probably lacking a naturally-acquired cluster-specific immune cross-protection. Among emergent emm types, emm75 and emm87 tend to become prevalent with a stable annual incidence and the risk of a clonal expansion have to be considered.
化脓链球菌或 A 组链球菌（GAS）可引起多种疾病，从简单的咽炎到危及生命的感染。它的流行病学非常复杂，由流行菌株的多样性、时间和地理波动所驱动。尽管 GAS 疾病的全球负担很重，但目前还没有针对 GAS 感染的可用疫苗策略。本研究基于一项纵向人群调查，旨在了解 GAS emm 型的动态，并更好地认识导致成功克隆出现的潜在机制。从 2009 年到 2017 年，我们在法国布列塔尼地区进行了一项基于系统培养的 GAS 感染的前瞻性临床数据恢复。使用 emm 分型结合所有回收菌株的结构和功能聚类分型系统进行流行病学分析。通过单因素分析确定的侵袭性危险因素，在多因素逻辑回归分析中进行计算，模型中唯一剩余的独立危险因素是年龄（整个范围的比值比[95%CI] = 6.35 [3.63, 11.10]；p<0.0001）。在确定的 61 种不同 emm 型中，最常见的是 emm28（16%）、emm89（15%）、emm1（14%）和 emm4（8%），它们占流行菌株的 50%以上。在研究期间，相继出现了 5 种基因型，分别为 emm44、66、75、83 和 87，它们属于与聚集“流行”emm 型（集群 A-C3 至 5、E1 和 E4）不同的 D4、E2、E3 和 E6 集群。我们之前报道过 emm44、66、83 和 75 型的显著遗传修饰，这可能是由于短期适应性进化所致。在此，我们还观察到，在具有特定危险因素或可能缺乏自然获得的群特异性免疫交叉保护的易感人群中，可能会出现新基因型的出现。在出现的 emm 型中，emm75 和 emm87 倾向于成为流行型，其年度发病率稳定，需要考虑克隆扩张的风险。
