Xu Xingxing, Bian Qiao, Luo Yun, Song Xiaojun, Lin Shan, Chen Huan, Liang Qian, Wang Meixia, Ye Guangyong, Zhu Bo, Chen Liang, Tang Yi-Wei, Wang Xianjun, Jin Dazhi
Department of Clinical Laboratory, Women's Hospital, Zhejiang University School of Medicine, Hangzhou, China.
School of Laboratory Medicine, Hangzhou Medical College, Hangzhou, China.
Front Microbiol. 2021 Jul 5;12:651520. doi: 10.3389/fmicb.2021.651520. eCollection 2021.
sequence type 2 (ST2) has been increasingly recognized as one of the major genotypes in China, while the genomic characteristics and biological phenotypes of Chinese ST2 strains remain to be determined. We used whole-genome sequencing and phylogenetic analysis to investigate the genomic features of 182 ST2 strains, isolated between 2011 and 2017. PCR ribotyping (RT) was performed, and antibiotic resistance, toxin concentration, and sporulation capacity were measured. The core genome Maximum-likelihood phylogenetic analysis showed that ST2 strains were distinctly segregated into two genetically diverse lineages [L1 (67.0% from Northern America) and L2], while L2 further divided into two sub-lineages, SL2a and SL2b (73.5% from China). The 36 virulence-related genes were widely distributed in ST2 genomes, but in which only 11 antibiotic resistance-associated genes were dispersedly found. Among the 25 SL2b sequenced isolates, RT014 (40.0%, = 10) and RT020 (28.0%, = 7) were two main genotypes with no significant difference on antibiotic resistance (χ = 0.024-2.667, > 0.05). A non-synonymous amino acid substitution was found in (Y1975D) which was specific to SL2b. Although there was no significant difference in sporulation capacity between the two lineages, the average toxin B concentration (5.11 ± 3.20 ng/μL) in SL2b was significantly lower in comparison to those in L1 (10.49 ± 15.82 ng/μL) and SL2a (13.92 ± 2.39 ng/μL) (χ = 12.30, < 0.05). This study described the genomic characteristics of ST2, with many virulence loci and few antibiotic resistance elements. The Chinese ST2 strains with the mutation in codon 1975 of the gene clustering in SL2b circulating in China express low toxin B, which may be associated with mild or moderate infection.
序列类型2（ST2）在中国已越来越被认为是主要基因型之一，而中国ST2菌株的基因组特征和生物学表型仍有待确定。我们使用全基因组测序和系统发育分析来研究2011年至2017年间分离出的182株ST2菌株的基因组特征。进行了PCR核糖体分型（RT），并测定了抗生素抗性、毒素浓度和芽孢形成能力。核心基因组最大似然系统发育分析表明，ST2菌株明显分为两个遗传上不同的谱系[L1（67.0%来自北美）和L2]，而L2进一步分为两个亚谱系，SL2a和SL2b（73.5%来自中国）。36个与毒力相关的基因广泛分布于ST2基因组中，但其中仅分散发现11个与抗生素抗性相关的基因。在25株测序的SL2b分离株中，RT014（40.0%，n = 10）和RT020（28.0%，n = 7）是两个主要基因型，在抗生素抗性方面无显著差异（χ² = 0.024 - 2.667，P > 0.05）。在基因中发现了一个非同义氨基酸替换（Y1975D），该替换是SL2b特有的。虽然两个谱系之间的芽孢形成能力没有显著差异，但与L1（10.49 ± 15.82 ng/μL）和SL2a（13.92 ± 2.39 ng/μL）相比，SL2b中的毒素B平均浓度（5.11 ± 3.20 ng/μL）显著较低（χ² = 12.30，P < 0.05）。本研究描述了ST2的基因组特征，其具有许多毒力位点和较少的抗生素抗性元件。在中国流行的SL2b中，基因密码子1975发生突变的中国ST2菌株表达低毒素B，这可能与轻度或中度感染有关。
