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Journal of Integrative Agriculture  2023, Vol. 22 Issue (2): 568-584    DOI: 10.1016/j.jia.2022.08.109
Animal Science · Veterinary Medicine Advanced Online Publication | Current Issue | Archive | Adv Search |
The vital role of CovS in the establishment of Streptococcus equi subsp. zooepidemicus virulence
XU Bin1, 2, MA Zhe1, 3, ZHOU Hong1, LIN Hui-xing1, FAN Hong-jie1, 3

1 MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, P.R.China

2 Key Laboratory of Veterinary Biological Engineering and Technology of Ministry of Agriculture and Rural Affairs, National Research Center of Veterinary Biologicals Engineering and Technology, Institute of Veterinary Medicine, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, P.R.China

3 Jiangsu Co-innovation Center for the Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, P.R.China

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目的:马链球菌兽疫亚种(Streptococcus equi subsp. zooepidemicus,SEZ)是一种人畜共患病病原,在我国主要引起猪链球菌病。本实验室前期研究发现了一株源于强毒株SEZ ATCC35246自然变异的弱毒株M35246M35246表现为一个连续25基因的丢失和covS基因的功能丧失性突变。这是第一次发现在SEZ中的涉及covS的自然变异。涉及covS的自然变异是增强化脓链球菌致病性的关键,所以需要确定covS的自然变异是否对SEZ毒力具有相同的影响。本工作的目的是研究CovSSEZ毒力形成中的作用有助于研究SEZ的致病机制,特别是涉及SEZ毒力的转录调控机制。

方法:本研究通过转录组测序和DNA测序,确定了M35246covS的碱基突变形式。在野生强毒株ATCC35246的基础上分别构建了25基因敲除株ΔPIcovS突变株McovS及对应的互补株。随后,本研究检测了ATCC35246M35246M35246 CcovSMcovSCMcovSΔPI的生长能力、对上皮细胞HEp-2黏附能力、对巨噬细胞Raw264.7的抗吞噬能力以及菌体荚膜含量;测定了ATCC35246M35246McovSΔPI24种抗生素的敏感性、对小鼠的半数致死量和攻毒后的菌体脏器分布;进行了ATCC35246M35246McovS的比较转录组学分析。


结论:本文系统研究了SEZ CovS在细菌抗吞噬作用、荚膜形成、致病性、抗生素耐药性以及各种重要毒力因子和关键代谢系统转录调控的作用。此外,转录组分析揭示了CovS在抗吞噬作用、荚膜形成、致病性和抗生素耐药性方面的调节机制。



Streptococcus equi subsp. zooepidemicus (SEZ) is an important zoonotic agent.  Here, a virulence-attenuated strain M35246 derived from natural variation of wild-type SEZ ATCC35246 was found.  M35246 showed a deletion of 25 contiguous genes as well as a loss-of-function mutation in covS.  Subsequently, a 25-gene-deleted strain (ΔPI), a covS-mutant strain (McovS), and relevant complementary strains were constructed and investigated.  M35246 and McovS were significantly less encapsulated and exhibited poorer anti-phagocytic capacity compared to wild-type SEZ.  McovS was significantly more sensitive to β-lactams, aminoglycosides, macrolides, and lincosamides than wild-type SEZ.  M35246, McovS, and ΔPI exhibited an increase in median lethal dose (LD50) in mice by 105, 105, and 5 times when compared to wild-type SEZ, respectively.  Neither M35246 nor McovS were isolated from mice 48 h after being challenged with approximately 2 000 times the LD50 of wild-type SEZ.  Transcriptome analysis showed that 668 significantly differentially expressed genes existed between McovS and wild-type SEZ.  Numerous virulence factor-encoding genes and anabolic-related genes in McovS that were involved in anti-phagocytosis, capsule formation, pathogenicity, and antibiotic resistance were downregulated significantly relative to the wild-type strain.  This study revealed that the CovS plays a vital role in the establishment of SEZ virulence

Keywords:  Streptococcus equi subsp. zooepidemicus       covS       natural variation       virulence       regulation  
Received: 07 December 2021   Accepted: 21 April 2022

This study was supported by the National Key Research and Development Program of China (2021YFD1800400), the National Natural Science Foundation of China (31872480), the Jiangsu Agriculture Science and Technology Innovation Fund, China (CX(19)2020), and the Priority Academic Program Development of Jiangsu Higher Education Institutions, China (PAPD).

About author:  XU Bin, E-mail:; Correspondence FAN Hong-jie, Tel/Fax: +86-25-84399592, E-mail:

Cite this article: 

XU Bin, MA Zhe, ZHOU Hong, LIN Hui-xing, FAN Hong-jie. 2023. The vital role of CovS in the establishment of Streptococcus equi subsp. zooepidemicus virulence. Journal of Integrative Agriculture, 22(2): 568-584.

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