Wan Xiulin, Li Xinhui, Osmundson Todd, Li Chunling, Yan He
School of Food Science and Engineering, South China University of Technology, Guangzhou, China.
Department of Microbiology, University of Wisconsin-La Crosse, La Crosse, United States of America.
PeerJ. 2020 Jun 22;8:e9293. doi: 10.7717/peerj.9293. eCollection 2020.
() is a respiratory pathogen of swine and the etiological agent of Glässer's disease. The structural organization of genetic information, antibiotic resistance genes, potential pathogenicity, and evolutionary relationships among global strains remain unclear. The aim of this study was to better understand patterns of genetic variation, antibiotic resistance factors, and virulence mechanisms of this pathogen.
The whole-genome sequence of a ST328 isolate from diseased swine in China was determined using Pacbio RS II and Illumina MiSeq platforms and compared with 54 isolates from China sequenced in this study and 39 strains from China and eigtht other countries sequenced by previously. Patterns of genetic variation, antibiotic resistance, and virulence mechanisms were investigated in relation to the phylogeny of the isolates. Electrotransformation experiments were performed to confirm the ability of pYL1-a plasmid observed in ST328-to confer antibiotic resistance.
The ST328 genome contained a novel Tn transposon harbouring a unique resistance determinant. It also contained a small broad-host-range plasmid pYL1 carrying and ; when transferred to RN4220 by electroporation, this plasmid was highly stable under kanamycin selection. Most (85.13-91.74%) of the genetic variation between isolates was observed in the accessory genomes. Phylogenetic analysis revealed two major subgroups distinguished by country of origin, serotype, and multilocus sequence type (MLST). Novel virulence factors ( and ) and drug resistance genes (, and ) in were identified Resistance determinants (, and ) were widespread across isolates, regardless of serovar, isolation source, or geographical location.
Our comparative genomic analysis of worldwide isolates provides valuable insight into the emergence and transmission of in the swine industry. The result suggests the importance of transposon-related and/or plasmid-related gene variations in the evolution of .
（）是猪的一种呼吸道病原体，也是猪传染性胸膜肺炎的病原体。全球菌株之间的遗传信息结构组织、抗生素抗性基因、潜在致病性和进化关系仍不清楚。本研究的目的是更好地了解这种病原体的遗传变异模式、抗生素抗性因素和毒力机制。
使用Pacbio RS II和Illumina MiSeq平台测定了一株来自中国患病猪的ST328分离株的全基因组序列，并与本研究中测序的54株中国分离株以及之前测序的39株来自中国和其他八个国家的菌株进行了比较。根据分离株的系统发育研究了遗传变异、抗生素抗性和毒力机制的模式。进行电转化实验以证实ST328中观察到的pYL1-a质粒赋予抗生素抗性的能力。
ST328基因组包含一个携带独特抗性决定簇的新型Tn转座子。它还包含一个携带和的小的广宿主范围质粒pYL1；当通过电穿孔转移到RN4220时，该质粒在卡那霉素选择下高度稳定。分离株之间大部分（85.13 - 91.74%）的遗传变异存在于辅助基因组中。系统发育分析揭示了两个主要亚组，它们由原产国、血清型和多位点序列类型（MLST）区分。在中鉴定出了新的毒力因子（和）和耐药基因（、和）抗性决定簇（、和）在分离株中广泛存在，与血清型、分离来源或地理位置无关。
我们对全球分离株的比较基因组分析为猪产业中猪传染性胸膜肺炎的出现和传播提供了有价值的见解。结果表明转座子相关和/或质粒相关基因变异在猪传染性胸膜肺炎进化中的重要性。
