Oakley C M
Department of Medicine (Clinical Cardiology), Hammersmith Hospital, London, U.K.
Eur Heart J. 1995 Apr;16 Suppl B:90-3. doi: 10.1093/eurheartj/16.suppl_b.90.
The most common cause for persistently negative blood cultures is the previous administration of antibiotics, but other causes include fastidious organisms (such as Brucella and Legionella), cell-dependent organisms (such as Chlamydia and Coxiella), fungi and a major immune reaction. Fastidious organisms may take up to 3 weeks to grow in optimal media. Abscess formation may take the organisms inaccessible. If the diagnosis is in doubt, echocardiography, and more specifically transoesophageal echocardiography, is invaluable. If the clinical diagnosis is made but cultures are unavailable or negative, treatment should be started without delay. The choice of antibiotic depends on the clinical setting. In general, penicillin and gentamicin are indicated for a subacute onset: flucloxacillin and gentamicin if the onset is acute. Intravenous drug abusers should receive vancomycin; those who have recently had a prosthetic valve inserted should receive vancomycin, together with rifampicin and gentamicin.
血培养持续呈阴性的最常见原因是先前使用过抗生素，但其他原因包括苛养菌（如布鲁氏菌和军团菌）、细胞内寄生菌（如衣原体和柯克斯体）、真菌以及严重的免疫反应。苛养菌在最佳培养基中可能需要长达3周的时间才能生长。脓肿形成可能使细菌难以被检测到。如果诊断存疑，超声心动图，尤其是经食管超声心动图，将非常有价值。如果已做出临床诊断但培养结果不可得或为阴性，应立即开始治疗。抗生素的选择取决于临床情况。一般来说，亚急性起病时选用青霉素和庆大霉素；急性起病时选用氟氯西林和庆大霉素。静脉药物滥用者应使用万古霉素；近期植入人工瓣膜者应使用万古霉素，同时加用利福平和庆大霉素。
