Institute for Microbiology, University of Veterinary Medicine, Hannover, Germany.
Central Facility for Microscopy, Helmholtz Centre for Infection Research, Braunschweig, Germany.
PLoS One. 2019 Jan 17;14(1):e0210801. doi: 10.1371/journal.pone.0210801. eCollection 2019.
Streptococcus suis is an economically important pathogen of pigs as well as a zoonotic cause of human disease. Serotyping is used for further characterization of isolates; some serotypes seem to be more virulent and more widely spread than others. This study characterizes a collection of German field isolates of Streptococcus suis from pigs dating from 1996 to 2016 with respect to capsular genes (cps) specific for individual serotypes and pathotype by multiplex PCR and relates results to the clinical background of these isolates. The most prominent finding was the reduction in prevalence of serotype-2/serotype-1/2 among invasive isolates during this sampling period, which might be attributed to widely implemented autogenous vaccination programs in swine against serotype 2 in Germany. In diseased pigs (systemically ill; respiratory disease) isolates of serotype-1/serotype-14, serotype-2/serotype-1/2, serotype 3 to 5 and 7 to 9 were most frequent while in carrier isolates a greater variety of cps types was found. Serotype-1/serotype-14 seemed to be preferentially located in joints, serotype 4 and serotype 3 in the central nervous system, respectively. The virulence associated extracellular protein factor was almost exclusively associated with invasive serotype-1/serotype-14 and serotype-2/serotype-1/2 isolates. In contrast, lung isolates of serotype-2/serotype-1/2 mainly harbored the gene for muramidase-released protein. Serotype 4 and serotype 9 isolates from clinically diseased pigs most frequently carried the muramidase-released protein gene and the suilysin gene. When examined by transmission electron microscopy all but one of the isolates which were non-typable by molecular and serological methods showed various amounts of capsular material indicating potentially new serotypes among these isolates. Given the variety of cps types/serotypes detected in pigs, not only veterinarians but also medical doctors should consider other serotypes than just serotype 2 when investigating potential human cases of Streptococcus suis infection.
猪链球菌是一种重要的猪病原体,也是人类疾病的人畜共患病病原体。血清型分析用于进一步鉴定分离株;一些血清型似乎比其他血清型更具毒力和更广泛传播。本研究通过多重 PCR 对来自 1996 年至 2016 年的德国猪源链球菌分离株的特定于个别血清型和血清型的荚膜基因 (cps) 进行了特征描述,并将结果与这些分离株的临床背景相关联。最显著的发现是在这一采样期间,侵袭性分离株中血清型 2/1/2 的流行率降低,这可能归因于在德国广泛实施的针对血清型 2 的猪同源疫苗接种计划。在患病猪(全身感染;呼吸道疾病)中,血清型 1/14、2/1/2、3 至 5 和 7 至 9 的分离株最为常见,而在携带分离株中发现了更多种类的 cps 型。血清型 1/14 似乎优先位于关节,血清型 4 和血清型 3 分别位于中枢神经系统。与侵袭性血清型 1/14 和 2/1/2 分离株相关的细胞外毒力相关蛋白因子几乎完全与该因子相关。相反,血清型 2/1/2 的肺分离株主要携带粘蛋白酶释放蛋白基因。来自临床患病猪的血清型 4 和 9 分离株最常携带粘蛋白酶释放蛋白基因和溶菌酶基因。通过透射电子显微镜检查,除了通过分子和血清学方法无法定型的分离株外,所有分离株均显示出不同数量的荚膜物质,表明这些分离株中存在潜在的新血清型。鉴于在猪中检测到的 cps 型/血清型种类繁多,兽医和医生在调查潜在的人类猪链球菌感染病例时,不仅应考虑血清型 2,还应考虑其他血清型。