What is the antibiotic of choice for native valve endocarditis?

From the Guidelines

The antibiotic of choice for native valve endocarditis is penicillin G or ceftriaxone for 4 weeks, as recommended for highly penicillin-susceptible viridans group streptococci and Streptococcus bovis. This recommendation is based on the guidelines from the American Heart Association, as outlined in the study published in Circulation in 2005 1. The study provides a detailed table outlining the recommended therapy for native valve endocarditis caused by highly penicillin-susceptible viridans group streptococci and Streptococcus bovis, with penicillin G or ceftriaxone being the preferred regimen.

Some key points to consider when treating native valve endocarditis include:

• The importance of obtaining blood cultures before starting antibiotics, when possible
• The need to adjust treatment based on susceptibility results
• The recommendation for early consultation with infectious disease specialists
• The importance of monitoring for complications such as heart failure, embolic events, and drug toxicity
• The use of vancomycin as an alternative for patients who are unable to tolerate penicillin or ceftriaxone, as outlined in the study published in Circulation in 2005 1

It is essential to note that the treatment of native valve endocarditis should be individualized based on the causative organism, the patient's medical history, and the presence of any complications. The guidelines provided in the studies 1 should be used as a reference to guide treatment decisions.

In terms of specific dosing regimens, the study published in Circulation in 2005 1 recommends the following:

• Penicillin G: 12-18 million units IV daily divided every 4 hours
• Ceftriaxone: 2g IV daily
• Vancomycin: 30 mg/kg per 24 hours IV in 2 equally divided doses, not to exceed 2g/24 hours unless serum concentrations are inappropriately low.

These dosing regimens should be adjusted based on the patient's renal function and other factors, as outlined in the study 1.

From the FDA Drug Label

Vancomycin Hydrochloride for Injection, USP is effective in the treatment of staphylococcal endocarditis Vancomycin Hydrochloride for Injection, USP has been reported to be effective alone or in combination with an aminoglycoside for endocarditis caused by S. viridans or S. bovis.

The antibiotic of choice for native valve endocarditis is vancomycin in certain cases, such as when methicillin-resistant staphylococci are suspected, or when the infection is caused by vancomycin-susceptible organisms that are resistant to other antimicrobial drugs.

• Vancomycin is effective for the treatment of staphylococcal endocarditis.
• Vancomycin can be used alone or in combination with an aminoglycoside for endocarditis caused by S. viridans or S. bovis. 2

From the Research

Native Valve Endocarditis Antibiotic Treatment

The choice of antibiotic therapy for native valve endocarditis depends on the identity and antibiotic susceptibility of the infecting organism.

• For streptococcal endocarditis, treatment with aqueous penicillin or ceftriaxone is effective 3.
• For enterococcal endocarditis, a combination of penicillin or ampicillin with gentamicin is appropriate, unless the strain is highly resistant to penicillin, in which case vancomycin should be substituted 3.
• For native valve infection by methicillin-susceptible staphylococci, treatment with nafcillin, oxacillin, or cefazolin is recommended, with the addition of gentamicin for the first three to five days to accelerate clearing of bacteremia 3.
• For penicillin-resistant viridans group streptococci, treatment regimens including penicillin and an aminoglycoside, or ceftriaxone monotherapy, have been successful 4.

Specific Antibiotic Regimens

• Penicillin G 20 million units per day i.v. for 4-6 weeks for penicillin-susceptible strains of staphylococci 5.
• A penicillinase-resistant penicillin (oxacillin) 2 g i.v. q 4 h for 4-6 weeks plus an aminoglycoside (gentamicin) 1.0 mg.kg-1 i.v. q 8 h for 1 week, for penicillin-resistant, methicillin-susceptible strains of staphylococci 5.
• Vancomycin 30 mg.kg.day-1 i.v. in 2-4 doses for 4-6 weeks, with the addition or not of rifampin 600-900 mg.day-1 orally, for methicillin-resistant strains of staphylococci 5.

General Treatment Guidelines

• The American Heart Association recommendations should be followed for the treatment of native valve endocarditis 3, 6.
• Treatment regimens should be guided by identification of the causative micro-organism and its antibiotic susceptibility 6.
• Vancomycin is recommended for patients allergic to penicillin or with methicillin-resistant staphylococcal endocarditis 3, 6, 7.