National Institute of Animal Health, Tsukuba, Ibaraki, Japan.
National Institute of Animal Health, Tsukuba, Ibaraki, Japan
Infect Immun. 2018 Aug 22;86(9). doi: 10.1128/IAI.00324-18. Print 2018 Sep.
causes swine erysipelas, an infection characterized by acute septicemia or chronic endocarditis and polyarthritis. Among 17 serovars, determined based on heat-stable peptidoglycan antigens, serovars 1 and 2 are most commonly associated with the disease; however, the molecular basis for the association between these serovars and virulence is unknown. To search for the genetic region defining serovar 1a (Fujisawa) strain antigenicity, we examined the 15-kb chromosomal region encompassing a putative pathway for polysaccharide biosynthesis, which was previously identified in the Fujisawa strain. Six transposon mutants of Fujisawa strain possessing a mutation in this region lost antigenic reactivity with serovar 1a-specific rabbit serum. Sequence analysis of this region in wild-type strains of serovars 1a, 1b, and 2 and serovar N, which lacks serovar-specific antigens, revealed that gene organization was similar among the strains and that serovar 2 strains showed variation. Serovar N strains displayed the same gene organization as the serovar 1a, 1b, or 2 strain and possessed certain mutations in this region. In two of the analyzed serovar N strains, restoration of the mutations via complementation with sequences derived from serovar 1a and 2 strains recovered antigenic reactivity with 1a- and 2-specific rabbit serum, respectively. Several gene mutations in this region resulted in altered capsule expression and attenuation of virulence in mice. These results indicate a functional connection between the biosynthetic pathways for the capsular polysaccharide and peptidoglycan antigens used for serotyping, which may explain variation in virulence among strains of different serovars.
导致猪丹毒，一种以急性败血性或慢性心内膜炎和多发性关节炎为特征的感染。在 17 个血清型中，根据耐热肽聚糖抗原确定，血清型 1 和 2 与该疾病最相关；然而，这些血清型与毒力之间关联的分子基础尚不清楚。为了寻找定义血清型 1a（藤泽）菌株抗原性的遗传区域，我们检查了包含多糖生物合成途径的 15kb 染色体区域，该途径先前在藤泽株中被鉴定。在该区域发生突变的藤泽株的 6 个转座子突变体失去了与血清型 1a 特异性兔血清的抗原反应性。野生型血清型 1a、1b 和 2 菌株和缺乏血清型特异性抗原的血清型 N 菌株中该区域的序列分析表明，菌株之间的基因组织相似，并且血清型 2 菌株表现出变异。血清型 N 菌株显示与血清型 1a、1b 或 2 菌株相同的基因组织，并在该区域具有某些突变。在分析的两个血清型 N 菌株中，通过用来自血清型 1a 和 2 菌株的序列互补来恢复突变，分别恢复了与 1a 和 2 特异性兔血清的抗原反应性。该区域的几个基因突变导致荚膜表达改变和小鼠毒力减弱。这些结果表明，荚膜多糖和用于血清分型的肽聚糖抗原的生物合成途径之间存在功能联系，这可能解释了不同血清型菌株之间毒力的差异。
