Department of Bacteriology, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
Vet Microbiol. 2013 Sep 27;166(1-2):281-5. doi: 10.1016/j.vetmic.2013.05.006. Epub 2013 May 25.
Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) is generally considered a commensal and an opportunistic pathogen of the upper airways in horses. Establishing whether certain strains of S. zooepidemicus can cause upper respiratory disease as a host-specific pathogen of horses, and if there are certain genogroups of S. zooepidemicus that are more virulent than others is of major clinical importance. In this study, we describe an outbreak of upper respiratory disease in horses that was associated with S. zooepidemicus. Upper respiratory samples were cultured, analyzed by real-time PCR for S. zooepidemicus and S. equi, and genetically differentiated by sequencing of the SzP protein gene and multi-locus sequence typing (MLST). Serum samples were analyzed for antibodies against S. equi and common viral respiratory pathogens. The ST-24 strain of S. zooepidemicus was isolated from all horses with clinical signs of disease, while the healthy horses carried other strains of S. zooepidemicus. Bacteriological, molecular and serological analyses strongly suggest that a single strain (ST-24) was responsible for the disease outbreak, and that certain strains of this presumed commensal may be more virulent than others.
马链球菌兽疫亚种（S. zooepidemicus）通常被认为是马上呼吸道的共生菌和机会致病菌。确定某些 S. zooepidemicus 菌株是否可以作为马的特定宿主病原体引起上呼吸道疾病，以及是否存在某些比其他菌株更具毒力的 S. zooepidemicus 基因群，这具有重要的临床意义。在本研究中，我们描述了与 S. zooepidemicus 相关的马的上呼吸道疾病暴发。对呼吸道样本进行培养，通过实时 PCR 对 S. zooepidemicus 和 S. equi 进行分析，并通过 SzP 蛋白基因测序和多位点序列分型（MLST）进行基因差异分析。对血清样本进行针对 S. equi 和常见病毒呼吸道病原体的抗体分析。从所有有临床疾病迹象的马中分离出 ST-24 株 S. zooepidemicus，而健康马携带其他 S. zooepidemicus 菌株。细菌学、分子和血清学分析强烈表明，单一菌株（ST-24）是疾病暴发的原因，并且这种假定的共生菌的某些菌株可能比其他菌株更具毒力。
