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Journal of Integrative Agriculture
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Molecular epidemiological and phenotypic characteristics of Streptococcus suis isolated in Hainan Island of China

Song Liang1, 2, 3, Shaoyan He2, 3, Shidan Zhang1, 2, 3, Jiqi Song1, 2, 3, Yubing Wang1, 2, 3, Xinyi Liu1, 2, 3, Lei Dai4, Jinxiu Wang4, Youzhi Xie4, Huochun Yao2, 3, Guangjin Liu1, 2, 3#

1Sanya Institute of Nanjing Agricultural University, Nanjing Agricultural University, Sanya 572025, China

2WOAH Reference Lab for Swine Streptococcosis, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.

3Key Laboratory of Animal Bacteriology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China

4Hainan Animal Disease Prevention and Control Center, Haikou 570203, China

 Highlights 

Serotypes 16 and 2 predominated among the 298 S. suis isolates, while 17.79% of the strains belonged to non-classical serotypes.

Two novel NCL subtypes (NCL3-3, NCL29-2) discovered in S. suis from diseased pigs in Hainan.

High-virulence isolates from healthy pigs showed a high genetic similarity to the Chinese epidemic strains 98HAH33 and 05ZYH33.

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摘要  

猪链球菌S. suis)是一种重要的全球性人畜共患病病原体,可引发人和猪的脑膜炎、关节炎等,严重时甚至导致死亡。海南作为中国唯一的热带岛屿,猪群中猪链球菌全年流行,人类感染风险较高。本研究旨在探究海南猪群猪链球菌的分子流行病学特征相关表型。2022年至2024我们从全岛采集了639份样本(含健康猪样本629份、病猪样本10份),共分离获得298株猪链球菌,平均分离率达46.63%。其中,血清型16型(占比22.15%)和2型(占比11.74%)为优势血清型,其次是7型(占比6.04%)和31型(占比5.37%),此外还有17.79%的菌株属于非经典血清型,其中我们鉴定出2个新NCL亚型(NCL3-3NCL29-263株代表性菌株开展全基因组测序,结果表明65.08%的菌株属于新型STs,这一发现反映出海南本土流行的猪链球菌具有独特的进化关系。值得关注的是,从健康猪分离出的菌株D74-2D77-1携带106个毒力相关基因(VAGs),在斑马鱼感染模型中展现出较强毒力,且与曾引发中国两次人类疫情的流行株98HAH3305ZYH33的进化关系最为密切。这一发现提示,海南健康猪群中的猪链球菌可能对公共卫生安全构成潜在威胁。无论测序菌株源自健康猪还是病猪,98.41%的菌株均表现出多重耐药表型。斑马鱼感染实验显示,所有SS2/ST1SS7/ST29菌株均为高毒力菌株,所有16型菌株均为低毒力菌株,同时分缺乏经典毒力标志物组合(mrp/sly/epfsrtF/ofsNisR/K)的菌株仍表现出高毒力。综上所述,本研究揭示了海南猪群中流行的猪链球菌具有复杂的分子流行病学特征及表型多样性,为中国热带地区该人畜共患病病原体的防控策略制定提供了科学依据。



Abstract  

Streptococcus suis (S. suis) is an important global zoonotic pathogen that can cause meningitis, arthritis, and even death in humans and pigs. Hainan, as the only tropical island in China, experiences a year-round prevalence of S. suis in swine and a high risk of human infection. This work aimed to investigate the molecular epidemiological and phenotypic characteristics of S. suis isolates from pigs in Hainan. Between 2022 and 2024, a total of 298 S. suis isolates were recovered from 639 samples (629 from healthy pigs and 10 from sick pigs) collected across Hainan Island. Serotype 16 (22.15%) and 2 (11.74%) strains exhibited the highest prevalence, followed by serotypes 7 (6.04%) and 31 (5.37%), while 17.79% of the strains belonged to non-classical serotypes. Whole-genome sequencing was conducted on 63 representative strains, and the genome data showed that 65.08% of the strains belonged to novel sequence types, which reflects the distinctive evolutionary relationships of strains originating from Hainan. Notably, D74-2 and D77-1, isolated from healthy pigs, exhibited high virulence with 106 virulence-associated genes (VAGs), and had the closest evolutionary relationship to the human strains 98HAH33 and 05ZYH33, which were responsible for two human outbreaks in China. Further, two new NCL subtypes (NCL3-3, NCL29-2) were identified from diseased pig-derived strains. Furthermore, 98.41% of sequenced strains exhibited multidrug resistance, irrespective of whether they originated from healthy or diseased pigs. Interestingly, all SS2/ST1 and SS7/ST29 strains were classified as highly virulent, whereas all SS16 strains were categorized as lowly virulent in zebrafish infection experiments. Nevertheless, our data showed that some strains lacking combinations of virulence markers (mrp/sly/epf, srtF/ofs, and NisR/K) still exhibited high virulence. In conclusion, the results presented above illustrate the diverse molecular epidemiological and phenotypic characteristics of S. suis in Hainan, providing a targeted scientific basis for the development of prevention and control strategies for this zoonotic pathogen in the Chinese tropical region

Keywords:  Streptococcus suis       molecular epidemiology              novel cps loci              virulence              multidrug resistance  
Online: 07 January 2026  
Fund: 

We thank Zongfu Wu (College of Veterinary Medicine, Nanjing Agricultural University) for providing strain SH040917. This work was supported by the General Program from the National Natural Science Foundation of China (32470199) and the scientific research grants from Hainan Province Science and Technology Special Fund (ZDYF2022XDNY236).

About author:  #Correspondence Guangjin Liu, E-mail: liugj100@njau.edu.cn; Song Liang, E-mail: vector12306@163.com

Cite this article: 

Song Liang, Shaoyan He, Shidan Zhang, Jiqi Song, Yubing Wang, Xinyi Liu, Lei Dai, Jinxiu Wang, Youzhi Xie, Huochun Yao, Guangjin Liu. 2026. Molecular epidemiological and phenotypic characteristics of Streptococcus suis isolated in Hainan Island of China. Journal of Integrative Agriculture, Doi:10.1016/j.jia.2026.01.008

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