Subacute infective endocarditis in the blood culture each time to draw 10 ml of blood, need to pay attention to is must be strict aseptic operation, to prevent the blood specimen is contaminated, arterial or venous blood can be, and should be every one hour not less than three consecutive blood collection, and then carry out the blood culture, at least two cultures of the same microorganisms can be a definitive diagnosis, but not necessarily in the fever or chills when Blood should be collected and both anaerobic and aerobic cultures should be performed. Special cultures should be done if fungal or rickettsial infections are being considered, and blood should be collected several days or a week after stopping antibiotics, and the results of the cultures should be observed for no less than 3 weeks, or 4-6 weeks in the case of Borrelia burgdorferi.