Infective Endocarditis: Treatment and Prophylaxis

Hana Saleh

Jonathan P. Moorman

INTRODUCTION

Empirical antibiotic treatment must be immediately started and targeted against the suspected organisms in patients with either native or prosthetic valve endocarditis.
Antibiotic therapy would then be modified according to the specific organism growing in blood cultures, its susceptibility, and the antibiotic minimum inhibitory concentration (MIC).
The antibiotic dose should be adjusted according to the patient’s renal function, and patients should be monitored for development of medication side effects.
Duration of antibiotic therapy starts from the time of first set of negative blood cultures.

ANTIBIOTIC THERAPY IN INFECTIVE ENDOCARDITIS:

I. Antibiotic regimens for treatment of infective endocarditis caused by streptococci and staphylococci species in patients with native valve and prosthetic valve are outlined in Table 29-1 and Table 29-2. The use of initial, low-dose gentamicin in the setting of native valve Staphylococcus aureus endocarditis appears to add nephrotoxicity and is no longer recommended.

It is recommended to rule out colon cancer or other gastrointestinal lesions in patients with bacteremia or endocarditis caused by Streptococcus bovis.

II. Antibiotic regimens for treatment of infective endocarditis caused by Streptococcus pneumoniae, Streptococcus pyogenes, and groups B, C, and G streptococci:

S. pneumoniae (highly susceptible to penicillin) or S. pyogenes: penicillin G IV, cefazolin, or ceftriaxone for 4 weeks. Vancomycin is considered as an alternative only in penicillin allergic patients.
S. pneumoniae (intermediately or highly resistant to penicillin): High-dose penicillin or a third-generation cephalosporin.
Groups B, C, and G streptococci: penicillin or cephalosporin for 4 to 6 weeks, plus gentamicin for 2 weeks

III. Antibiotic regimens for treatment of infective endocarditis caused by enterococci species in patients with native valve and prosthetic valve are outlined in Table 29-3.

Table 29-1 Treatment of Endocarditis Caused by Streptococci and Staphylococci Species in Patients with Native Valve

Organism		Antimicrobial Regimen	Alternative Regimen^a
Viridans group streptococci and S. bovis	MIC ≤0.12 µg/mL (highly susceptible to penicillin)	Penicillin G 12-18 million U IV per day, in a continuous infusion, or given in four to six doses, for 4 weeks	Vancomycin 30mg/kg divided in two IV doses per day (not more than 2g/day), for 4 weeks
		Penicillin G 12-18 million U IV per day, plus gentamicin 3mg/kg IV/IM once daily, for 2 weeks Ceftriaxone 2g IV once daily, plus gentamicin 3mg/kg IV/IM once daily, for 2 weeks
	MIC >0.12 and ≤0.5 µg/mL (relative resistance to penicillin)	Penicillin G 24 million U IV per day, for 4 weeks, plus gentamicin 3mg/kg IV/IM once daily, for 2 weeks	Vancomycin 30mg/kg divided in two IV doses per day (not more than 2g/day), for 4 weeks
		Ceftriaxone 2g IV once daily, for 4 weeks, plus gentamicin 3mg/kg IV/IM once daily, for 2 weeks
Staphylococci (S. aureus or coagulase-negative staphylococci)	Methicillin-sensitive	Nafcillin or oxacillin^b 12g/day IV in four to six doses, for 6 weeks	Cefazolin^c 6g/day IV in three doses, for 6 weeks
	Methicillin-resistant	Vancomycin 30mg/kg divided in two IV doses per day, (not more than 2g/day), for 6 weeks^d	Daptomycin 6mg/kg daily for 6 weeks Daptomycin 6mg/kg daily for 6 weeks
Some experts believe vancomycin dose should be adjusted for a trough level of 10-20 µg/mL.
^aAlternative therapy to be used in patients with penicillin intolerance
^bIn cases of uncomplicated right-sided endocarditis, 2-week therapy with nafcillin/oxacillin plus gentamicin can be used.
^cSubstitute with vancomycin if history of anaphylaxis to penicillin is present.
^dDaptomycin should be considered for treatment of methicillin-resistant S. aureus, if MIC to vancomycin is >1 µg/mL.
MIC, minimum inhibitory concentration.
Modified from Baddour LM, Taubert KA, et al. Infective endocarditis: diagnosis, antimicrobial therapy, and management of complications: a statement for healthcare professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young, and the Councils on Clinical Cardiology, Stroke, and Cardiovascular Surgery and Anesthesia, American Heart Association. Circulation 2005;111(23):e394-e434.

Table 29-2 Treatment of Endocarditis Caused by Streptococci and Staphylococci Species in Patients with Prosthetic Valve

Organism		Antimicrobial Regimen	Alternative Regimen^a
Viridans group streptococci and S. bovis	MIC ≤0.12 µg/mL (highly susceptible to penicillin)	Penicillin G 24 million U IV per day, for 6 weeks, ± gentamicin 3 mg/kg IV/IM once daily, for 2 weeks	Vancomycin 30mg/kg divided in 2 IV doses per day, (not more than 2g/day), for 6 weeks
		Ceftriaxone 2g IV once daily, for 6 weeks, ± gentamicin 3mg/kg IV/IM once daily, for 2 weeks
	MIC >0.12 (relative or complete resistance to penicillin)	Penicillin G 24 million U IV per day, for 6 weeks, plus gentamicin 3mg/kg IV/IM once daily, for 6 weeks	Vancomycin 30mg/kg divided in two IV doses per day, (not more than 2g/day), for 6 weeks
		Ceftriaxone 2g IV once daily, for 6 weeks, plus gentamicin 3mg/kg IV/IM once daily, for 6 weeks
Staphylococci (S. aureus, or coagulase-negative staphylococci)	Methicillin-sensitive	Nafcillin or oxacillin^b 12g/day IV in four to six doses, for ≥6 weeks, plus rifampin 900mg/day in 3 doses, for ≥6 weeks, plus gentamicin 3 mg/kg IV/IM per day in two to three doses, for 2 weeks
	Methicillin-resistant	Vancomycin 30mg/kg divided in two IV doses per day, (not more than 2g/day), for ≥6 weeks, plus rifampin 900mg/day in three doses, for ≥6 weeks, plus gentamicin 3 mg/kg IV/IM per day in two to three doses, for 2 weeks
^aAlternative therapy to be used in patients with penicillin intolerance
^bCan substitute nafcillin or oxacillin with penicillin G 24 million U IV per day in four to six doses, if the staphylococcus strain is penicillin-sensitive (MIC ≤0.1 µg/mL)
Some experts believe vancomycin dose should be adjusted for a trough level of 10-20 µg/mL.
MIC, minimum inhibitory concentration
Modified from Baddour LM, Taubert KA, et al. Infective endocarditis: diagnosis, antimicrobial therapy, and management of complications: a statement for healthcare professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young, and the Councils on Clinical Cardiology, Stroke, and Cardiovascular Surgery and Anesthesia, American Heart Association. Circulation 2005;111:e394-e434.