Streptococcus equi subsp. zooepidemicus is an emerging pathogen of pigs, resulting in high-mortality outbreaks of septicaemia and abortions. Here, we investigated the early pathogenesis of S. zooepidemicus in pigs following oronasal inoculation. Fourteen pigs were inoculated with live cultures of S. zooepidemicus ST-194, and monitored at 2,4, 8, and 24 h post-inoculation. Necropsies were performed to assess gross lesions and collect samples for bacterial culture and PCR analysis at each time point. Our findings revealed that S. zooepidemicus was detectable in various organs as early as 2 h post-inoculation, including liver and spleen, demonstrating rapid dissemination within the host. Tonsil samples consistently harboured live S. zooepidemicus throughout the study period, suggesting their potential for epidemiological sampling and diagnostics. Moreover, the presence of varying bacterial loads in mesenteric lymph nodes indicated persistence, replication, and a potential source for shedding. Further studies are required to determine the initial site of replication.

马链球菌亚种 兽疫弧菌是一种新出现的猪病原体，可导致败血症和流产的高死亡率暴发。在这里，我们研究了猪口鼻接种后兽疫链球菌的早期发病机制。十四头猪接种了兽疫链球菌ST-194 活培养物，并在接种后 2,4、8 和 24 小时进行监测。进行尸检以评估肉眼病变，并在每个时间点收集样本进行细菌培养和 PCR 分析。我们的研究结果表明，早在接种后 2 小时就可以在包括肝脏和脾脏在内的多个器官中检测到兽疫链球菌，这表明兽疫链球菌在宿主内快速传播。在整个研究期间，扁桃体样本始终含有活的兽疫链球菌，这表明它们具有流行病学采样和诊断的潜力。此外，肠系膜淋巴结中存在不同的细菌负荷表明存在持久性、复制性和潜在的脱落来源。需要进一步的研究来确定复制的初始位点。