College of Life Sciences, Beijing Normal University, Beijing, 100875, China; National Institute of Biological Sciences, Zhongguancun Life Science Park, Changping, 102206, Beijing, China; Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, 102206, Beijing, China.
Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Microb Pathog. 2020 Oct;147:104416. doi: 10.1016/j.micpath.2020.104416. Epub 2020 Jul 31.
Streptococcus agalactiae is a serious pathogen causing severe anthropozoonosis in a broad range of hosts, from aquatic animals to mammals, including humans. S. agalactiae HZAUSC001 was isolated from a moribund tilapia fish exhibiting classic clinical symptoms of streptococcosis in Zhanjiang, Guangdong, China. And it was identified as the etiological factor resulting in fish disease, but was notable because it exhibited attenuated virulence. Here, the genome of S. agalactiae HZAUSC001 was re-analyzed; we assessed the resistome and virulome and deciphered the attenuated characters of HZAUSC001. The S. agalactiae HZAUSC001 genome was assembled into one chromosome with a GC-content of 35.37% and 1972 predicted open reading frames (ORFs). Phylogenetic analysis indicated that it is evolutionarily similar to piscine GBS strains GD201008-001 and ZQ0910. After re-analyzing the published genomic sequence of HZAUSC001, we identified 38 virulence factor genes and one antibiotic-resistance gene. Note that three previously noted virulence genes, bca (C protein alpha-antigen), cpbA (choline-binding protein A) and esp (enterococcal surface protein), were absent in the virulence-attenuated strain S. agalactiae HZAUSC001 but present in the highly virulent strain S. agalactiae GD201008-001. We speculate that the absence of these three virulence genes may be associated with the attenuated traits of the HZAUSC001 strain. Collectively, our study supports that HZAUSC001 may be an excellent candidate for development of an attenuated vaccine, and our results contribute to further understanding of GBS epidemiology and surveillance targets.
无乳链球菌是一种严重的病原体，能引起包括人类在内的广泛宿主的严重人畜共患病。无乳链球菌 HZAUSC001 是从广东湛江一条濒临死亡的罗非鱼中分离出来的，该鱼表现出经典的链球菌病临床症状。它被鉴定为导致鱼类疾病的病因，但值得注意的是，它表现出减弱的毒力。在这里，我们重新分析了无乳链球菌 HZAUSC001 的基因组；评估了耐药组和毒力组，并破译了 HZAUSC001 的衰减特征。无乳链球菌 HZAUSC001 的基因组被组装成一条染色体，GC 含量为 35.37%，有 1972 个预测的开放阅读框（ORFs）。系统发育分析表明，它与鱼类 GBS 株 GD201008-001 和 ZQ0910 在进化上相似。在重新分析 HZAUSC001 的已发表基因组序列后，我们鉴定了 38 个毒力因子基因和 1 个抗生素耐药基因。值得注意的是，在毒力减弱的无乳链球菌 HZAUSC001 菌株中，以前注意到的三个毒力基因 bca（C 蛋白α-抗原）、cpbA（胆碱结合蛋白 A）和 esp（肠球菌表面蛋白）缺失，但在高毒力菌株无乳链球菌 GD201008-001 中存在。我们推测，这三个毒力基因的缺失可能与 HZAUSC001 菌株的衰减特性有关。总的来说，我们的研究支持 HZAUSC001 可能是一种开发减毒疫苗的优秀候选者，我们的结果有助于进一步了解 GBS 的流行病学和监测目标。
