A Rare Case of Cardiac Device Related Infective Endocarditis Caused by Streptococcus Infantarius Subspecies Coli (S. Bovis Biotype II/1)

Streptococcus bovis (formerly group D streptococci) is a catalase-negative, gram-positive cocci in pairs or chains that are resident of the gastrointestinal microbiota of humans. These opportunistic pathogens are associated with various human diseases, including infective endocarditis and colonic neoplasm. We present the case of a 73-year-old male with significant cardiac history who presented after a syncopal episode following Implantable cardioverter defibrillator (ICD) multiple firing with blood cultures positive for Streptococcus infantarius subspecies coli (S. bovis biotype II/1) formerly known as Streptococcus lutiensis. Transesophageal echocardiography showed echodensity attached to the ICD lead that was suspicious for vegetation. CT abdomen and pelvis findings suggested splenic infarction, indicating embolization secondary to Infective endocarditis. Although previous studies have indicated that the S.bovis subspecies have varying propensities to cause IE, with S.gallolyticus accounting for the majority of IE cases, there is still insufficient data about the incidence of IE with other subspecies of S.bovis. We will discuss the incidence of IE with S.infantarius subspecies coli of S.bovis and the importance of considering echocardiography in bacteremia with S.infantarius.牛链球菌（Streptococcus bovis，原归类为D群链球菌）是一种过氧化氢酶阴性的革兰阳性球菌，常以成双或链状排列，为人类胃肠道菌群的常驻成员。该类机会致病菌可引发多种人类疾病，包括感染性心内膜炎与结肠肿瘤。 本文报告一例73岁男性患者，该患者有明确心脏病史，因植入式心脏复律除颤器（Implantable cardioverter defibrillator, ICD）多次放电后出现晕厥发作就诊，其血培养结果呈阳性，检出婴儿链球菌结肠亚种（Streptococcus infantarius subspecies coli，原归类为牛链球菌生物型II/1，曾称路蒂链球菌Streptococcus lutiensis）。经食管超声心动图检查可见附着于ICD导线的回声团块，高度疑似感染性赘生物。腹部及盆腔CT检查提示脾梗死，提示存在感染性心内膜炎继发的栓塞事件。 尽管既往研究显示，牛链球菌各亚种引发感染性心内膜炎（Infective Endocarditis, IE）的倾向存在差异，其中解脲链球菌（S. gallolyticus）占感染性心内膜炎病例的绝大多数，但目前关于牛链球菌其他亚种引发感染性心内膜炎的发病数据仍较为匮乏。本文将探讨牛链球菌婴儿结肠亚种引发感染性心内膜炎的发病情况，以及在婴儿链球菌菌血症患者中开展超声心动图检查的重要临床价值。