The pathogenic equine streptococci

Abstract

-Streptococci pathogenic for the horse include S. equi (S. equi subsp. equi), S. zooepidemicus (S. equi subsp. zooepidemicus), S. dysgalactiae subsp. equisimilis and S. pneumoniae capsule Type III. S. equi is a clonal descendent or biovar of an ancestral S. zooepidemicus strain with which it shares greater than 98% DNA homology and therefore expresses many of the same proteins and virulence factors. Rapid progress has been made in identification of virulence factors and proteins uniquely expressed by S. equi. Most of these are expressed either on the bacterial surface or are secreted. Notable examples include the antiphagocytic SeM and the secreted pyrogenic superantigens SePE-I and H. The genomic DNA sequence of S. equi will greatly accelerate identification and characterization of additional virulence factors and vaccine targets. Although it is the most frequently isolated opportunist pyogen of the horse, S. zooepidemicus has been the subject of few contemporary research studies. Variation in the protectively immunogenic SzP proteins has, however, been well characterized. Given its opportunist behavior, studies are urgently needed on regulation of virulence factors such as capsule and proteases. Likewise, information is also very limited on virulence factors and associated gene regulation of S. dysgalactiae subspecies equisimilis. It has recently been shown that equine isolates of Streptococcus pneumoniae are clonal, a feature shared with S. equi. All equine isolates express capsule Type III, are genetically similar, and have deletions in the genes for autolysin and pneumolysin. In summary, the evolving picture of the interaction of the equine pathogenic streptococci and their host is that of multiple virulence factors active at different stages of pathogenesis. The inherent complexity of this interaction suggests that discovery of effective combinations of immunogens from potential targets identified in genomic sequence will be laborious.

Perfil fenotípico e susceptibilidade antimicrobiana de Streptococcus equi isolados de equinos da região Sul do Brasil

“…No entanto, para os isolados de S. equi subsp. equi, o padrão de colônias foi variável, o que confirma que esta característica fenotípica não pode ser utilizada para diferenciar estas subespécies (Timoney 2004 (Grant et al 1993), o que justifica a classificação de duas cepas de S. equi como atípicas, pois eram fermentadoras de lactose.…”

“…A diferenciação entre os subtipos é realizada de forma rotineira pela utilização de técnicas fenotípicas, como a fermentação de açúcares (Timoney 2004). O grupo C de Lancefield, do qual faz parte S. equi, apresenta três espé-cies, classificadas de acordo com a produção de hemólise e capacidade de fermentação de trealose, sorbitol e lactose (Lancefield 1933, Quinn et al 1994, Kuwamoto et al 2001.…”

Biochemical characteristics and antimicrobials susceptibility of pathogenic Streptoccus spp. isolated from respiratory tract of Thoroughbred horses in Jeju, Korea

“…면양 혈액 5% 첨가배지에서 발육 증식하며, 대부분은 용혈성을 나타내지만 혈액배지 상의 용혈 양상에 따라 α, β, γ 용혈성 streptococci로 분류하기도 한다. 또한, streptococci의 균체 항원성을 나타내는 C 다당체의 특성에 따라 혈청학적으로 Lancefield group A부터 T까지의(I, J 제외) 18종의 군으로 한다 (Whitworth, 1990 (Timoney, 2004;Preziuso 등, 2010). 이번 연구에서 분리된 S. equisimilis는 말의 호흡기 감염 및 림프절 감염 등의 보고가 있으나 높은 빈도 로 감염을 유발하는 원인체는 아닌 것으로 알려졌으 며, S. equisimilis는 건강한 개체로부터 분리되어 감염 증 발생과의 상관관계는 확인할 수 없었다.…”

Characterization of the haem-uptake system of the equine pathogen Streptococcus equi subsp. equi

“…equi (herein referred to as S. equi) is the causative agent of strangles, one of the most feared diseases of horses. Strangles is a highly contagious disease of the upper respiratory tract characterized by abscessation of lymph nodes in the head and neck (Timoney, 1993(Timoney, , 2004 et al, 2006b). Here, we demonstrate that S. equi expresses these two proteins and also a truncated Shr homologue (designated SeShr) under conditions of iron-limitation.…”

“…S. equi is considered to have evolved from S. equi subsp. zooepidemicus (herein referred to as S. zooepidemicus; Chanter et al, 1997), an opportunistic mucosal commensal which can cause serious diseases in a range of animals and, occasionally, humans (Timoney, 2004).…”