Genome diversity of spatially distinct Streptococcus agalactiae. Genome diversity of spatially distinct Streptococcus agalactiae

"Streptococcus agalactiae clones infecting humans were selected and fixed through the extensive use of tetracycline." Pubmed ID: 25088811. Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal of the digestive and genitourinary tracts of humans that emerged as the leading cause of bacterial neonatal infections in Europe and North America during the 1960s. Due to the lack of epidemiological and genomic data, the reasons for this emergence are unknown. Here we show by comparative genome analysis and phylogenetic reconstruction of 229 isolates that the rise of human GBS infections corresponds to the selection and worldwide dissemination of only a few clones. The parallel expansion of the clones is preceded by the insertion of integrative and conjugative elements conferring tetracycline resistance (TcR). Thus, we propose that the use of tetracycline from 1948 onwards led in humans to the complete replacement of a diverse GBS population by only few TcR clones particularly well adapted to their host, causing the observed emergence of GBS diseases in neonates.

导致人类感染的无乳链球菌（Streptococcus agalactiae）克隆株，因四环素的广泛使用而被筛选并固定存续。PubMed编号：25088811。无乳链球菌（B群链球菌，GBS）是人类消化道与泌尿生殖道的共生菌群，于20世纪60年代在欧洲和北美成为新生儿细菌性感染的首要致病菌。由于当时缺乏流行病学与基因组学相关数据，其出现暴发的具体原因至今不明。本研究通过对229株分离株的比较基因组分析与系统发育重建，证实人类GBS感染率的上升，仅对应少数克隆株的筛选与全球播散。这些克隆株的平行扩张，始于可赋予四环素耐药性（TcR）的整合接合元件的插入。因此，我们提出：自1948年起四环素的临床使用，使得人类体内多样化的GBS种群被少数几株高度适配宿主的TcR克隆株完全取代，进而引发了观测到的新生儿GBS疾病流行。