The treatment of endocarditis mandates the use of bactericidal antimicrobials. The administration of bactericidal antimicrobials such as metronidazole alone or combined with clindamycin was more effective in preventing experimental endocarditis than were bacteriostatic agents such as clindamycin, chloramphenicol (31), cefoxitin or erythromycin. Similar experiences were noted in a limited number of patients (32).
Carbapenems (i.e., imipenem, merpenem) should be effective for anaerobic endocarditis, including B. fragilis group. Patients with endocarditis caused by penicillin-susceptible anaerobic microorganisms such as Peptostreptococci should receive therapy with penicillin G or vancomycin, and those unable to receive penicillin should be treated with metronidazole or clindamycin if the organism is susceptible to these agents.
Presumptive antimicrobial therapy is based on the patient's age, pre-existing cardiac condition, and other risk factors such as intravenous drug use, surgery, and previous episodes of bacteremia or endocarditis.
For therapy of aerobic and facultatives bacteria, a beta-lactamase-resistant penicillin or vancomycin are chosen because of their activity against staphylococci and streptococci. An aminoglycoside is given for synergistic interaction with those agents against enterococci and other streptococcal species and to cover aerobic or facultative gram-negative bacilli. If blood cultures do not show growth but the patient responds to treatment, initially selected antibiotics are not stopped while other methods of diagnosis are continued. If the blood cultures are positive, antibiotic treatment is then based on the susceptibility test results.
Therapy is given intravenously for four to six weeks. Individuals with prosthetic intravascular valves are treated for six weeks.
Surgical intervention may be indicated (33) for abscess of the valve annulus or myocardium, two or more embolic events, rupture of valve leaflet or chordae, valvular insufficiency, rupture of an aneurysm of the sinus of Valsalva, conduction disturbances caused by a septal abscess, deteriorating cardiac failure, and inability to sterilize the blood. Removal of prosthetic valves may be indicated if medical therapy fails.
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