An 8-y-old jenny was presented because of anorexia and mild depression. The jenny had weaned her colt 10 d before the admission. Upon arrival at the University of Illinois Veterinary Teaching Hospital, the heart rate was elevated, and the right udder was painful and swollen on palpation. Milk stripping of the affected side revealed purulent content; the contralateral udder had normal-appearing milk. Cytology of mammary gland secretions from the affected side revealed a large number of hypersegmented reactive neutrophils with phagocytized bacteria. Complete blood count, serum chemistry, and fibrinogen were within normal limits. A diagnosis of clinical mastitis was made, and the jenny was started on a 5-d course of broad-spectrum antibiotics, a non-steroidal anti-inflammatory, hydrotherapy, and milk stripping. Clinical signs reduced over time, and the cure was attained by 96 h post-admission. Aerobic culture and subsequent MALDI-TOF MS analysis identified a bacterium of the Streptococcus genus but not the species. Whole-genome analysis was performed, and 16S rDNA sequencing and analysis determined that our isolate 20-37394 clustered with 2 other Streptococcus strains (27284-01 and 28462). Single-nucleotide variations and phylogenetic tree analysis revealed that Streptococcus 20-37394 had 96.8% and 94.9% identities to Streptococcus strains 27284-01 and 28462, respectively; therefore, the bacteria isolated in our case was deemed as a new Streptococcus species.

一个 8 岁的 jenny 因厌食和轻度抑郁而出现。珍妮在入院前 10 天给小马断奶。到达伊利诺伊大学兽医教学医院后，心率升高，触诊右侧乳房疼痛肿胀。患侧乳汁剥脱，可见脓性内容物；对侧乳房有正常外观的乳汁。患侧乳腺分泌物的细胞学显示大量具有吞噬细菌的高分节反应性中性粒细胞。全血细胞计数、血清化学和纤维蛋白原均在正常范围内。诊断为临床乳腺炎，珍妮开始接受 5 天的广谱抗生素疗程、非甾体抗炎药、水疗和脱奶治疗。临床症状随着时间的推移而减少，入院后96小时治愈。需氧培养和随后的 MALDI-TOF MS 分析鉴定了一种细菌链球菌属但不是种。进行了全基因组分析，16S rDNA 测序和分析确定我们的分离株 20-37394 与 2 个其他链球菌菌株（27284-01 和28462）聚集在一起。单核苷酸变异和系统发育树分析显示，链球菌20-37394 与链球菌菌株 27284-01 和 28462 分别具有 96.8% 和 94.9% 的同一性；因此，我们病例中分离出的细菌被认为是一种新的链球菌。