Dr. Hall, Sweden, summarized previously published literature on antibiotic prophylaxis for post-operative oral bacteraemia and infective endocarditis (IE) and concluded that prophylactic use of antibiotics after oral surgery reduces the incidence of post-operative bacteraemia and is the most important factor in preventing IE, especially in high-risk cardiac patients. 1. Oral-derived bacteraemia Dental treatment is often considered a major cause of IE because of the high incidence of bacteraemia after invasive oral operations. Due to the application of anaerobic culture techniques and new blood culture techniques (such as hemolysis-filtration techniques) in recent years, the positive rate of postoperative bacteraemia has increased significantly compared to the past. The incidence of bacteraemia after various dental procedures varied: 40% for tooth extraction, 35% for scaling, 42% for endodontic surgery, 58% for periodontal surgery, and 34% for tonsil removal. Among them, the culture positivity rate of anaerobic bacteria is higher than aerobic bacteria, and Streptococcus griseus is the most frequently isolated bacteria. 2, antibiotic prophylaxis of IE For ethical and statistical reasons, prospective clinical studies of antibiotic prophylaxis of IE in the population cannot be conducted. A large number of studies in animal models of IE have found that prophylactic antibiotics can reduce the occurrence of IE. The mechanism is that antibiotics kill bacteria in the blood circulation, interfere with bacterial adhesion to the flab, and inhibit the growth of bacteria on the flab, thus allowing other defense mechanisms to gradually remove bacteria from the flab. Theoretically, an effective reduction in the incidence and severity of bacteremia could reduce the incidence of IE. Numerous studies have shown that prophylactic administration of antibiotics prior to oral surgery can be effective in reducing the incidence of bacteremia. However, some researchers have concluded that preoperative antibiotics do not reduce the incidence of bacteremia. Clinical studies have demonstrated the effectiveness of some case-control studies; while some case reports have concluded that prophylactic antibiotics are not effective in reducing the occurrence of IE. 3. The main principles and protocols of antibiotic prophylaxis for IE are to first identify high-risk cardiac patients (e.g., with prosthetic valves, cyanotic congenital heart disease, history of IE, valve dysfunction with regurgitation, non-cyanotic congenital heart disease, hypertrophic obstructive cardiomyopathy, etc.); then identify risky operations (e.g., all dental operations that can lead to gingival and mucosal bleeding); administer bactericidal antibiotics, and for a period of approximately 9 hour risk period to a serum concentration that exceeds the minimum inhibitory concentration (MIC) for the bacteria most likely to cause IE. The American College of Cardiology used to recommend a regimen of 3 g of oral amoxicillin 1 hour before surgery, followed by 1.5 g 6 hours later, and in 1997 changed to a single dose of 2 g of amoxicillin. Because serum amoxicillin concentrations can be maintained at MICs greater than those of most oral streptococci for long periods of time, and because blood amoxicillin maintains inhibition of these strains for 6 to 14 hours, those allergic to penicillin are switched to clindamycin, cefadroxil, cefadroxil, azithromycin, and methylerythromycin. The standard regimen recommended by the International Society for Chemotherapy is 3 g of amoxicillin orally preoperatively, or 300 to 600 mg of clindamycin orally for those allergic to penicillin. Some special patients, such as patients with high-risk heart disease, multiple surgeries and general anesthesia, are recommended to be administered with amoxicillin 2g intravenously plus gentamicin 1.5mg/kg intravenously, or vancomycin 1g plus gentamicin 1.5mg/kg intravenously for those allergic to penicillin.