How should antibiotics be chosen for the treatment of infective endocarditis (IE)?

Updated: Jan 03, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Prolonged administration of intravenous antibiotics remains the mainstay of treatment for IE.

In the setting of acute IE, institute antibiotic therapy as soon as possible to minimize valvular damage. Three to 5 sets of blood cultures are obtained within 60-90 minutes, followed by the infusion of the appropriate antibiotic regimen. By necessity, the initial antibiotic choice is empiric in nature, determined by clinical history and physical examination findings.

Empiric antibiotic therapy is chosen based on the most likely infecting organisms. Native valve endocarditis (NVE) has often been treated with penicillin G and gentamicin for synergistic coverage of streptococci. Patients with a history of intravenous (IV) drug use have been treated with nafcillin and gentamicin to cover for methicillin-sensitive staphylococci. The emergence of methicillin-resistant S aureus (MRSA) and penicillin-resistant streptococci has led to a change in empiric treatment with liberal substitution of vancomycin in lieu of a penicillin antibiotic.

Prosthetic valve endocarditis (PVE) may be caused by MRSA or coagulase-negative staphylococci (CoNS) [18] ; thus, vancomycin and gentamicin may be used for treatment, despite the risk of renal insufficiency. Rifampin is necessary in treating individuals with infection of prosthetic valves or other foreign bodies because it can penetrate the biofilm of most of the pathogens that infect these devices. However, it should be administered with vancomycin or gentamicin. These latter 2 agents serve to prevent the development of resistance to the rifampin.

Substitution of linezolid for vancomycin should be considered in patients with unstable renal function because of the difficulty of achieving therapeutic trough levels in this situation.

Linezolid or daptomycin are options for patients with intolerance to vancomycin or resistant organisms. [80] Organisms with a minimum inhibitory concentration (MIC) to vancomycin of equal to or greater than 2 mcg/mL should be treated with alternative agents. Appropriate regimens should be devised in consultation with a specialist in infectious disease.

In the case of subacute IE, treatment may be safely delayed until culture and sensitivity results are available. Waiting does not increase the risk of complications in this form of the disease.

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