Medication Summary
Antibiotics are used in the treatment of bacterial endocarditis and are also employed for prophylaxis.
Antimicrobial Agents
Class Summary
Treatment with antibiotics is specific to the etiologic agent and its characteristics. Therapy for penicillin-susceptible streptococcal endocarditis (PSSE), penicillin-resistant streptococcal endocarditis (PRSE), enterococcal endocarditis, methicillin-susceptible S aureus (MSSA), methicillin-resistant S aureus (MRSA), endocarditis caused by HACEK organisms (ie, Haemophilus parainfluenzae, H aphrophilus, H paraphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, or Kingella species), and fungal endocarditis are aimed at total eradication of the organism.
After antibiotic treatment, patients with endocarditis remain at high risk for recurrence and for complications of a recurrence. These patients are still recommended to receive prophylactic antibiotics for dental procedures involving manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa and for respiratory tract procedures that involve incision or biopsy of the respiratory mucosa. [7]
Penicillin G (Pfizerpen)
This is a first-line agent. It interferes with the synthesis of cell-wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms.
Ampicillin (Omnipen, Principen)
Ampicillin has bactericidal activity against susceptible organisms. It is an alternative to amoxicillin when the patient cannot take oral medication. Bacterial endocarditis that is found to be a methicillin-susceptible S aureus (MSSA) infection on native valves is treated with nafcillin or oxacillin for at least 6 weeks.
Nafcillin (Unipen, Nafcil)
Ampicillin has bactericidal activity against susceptible organisms. It is an alternative to amoxicillin when the patient cannot take oral medication. Bacterial endocarditis that is found to be a methicillin-susceptible S aureus (MSSA) infection on native valves is treated with nafcillin or oxacillin for at least 6 weeks.
Oxacillin (Bactocill, Prostaphlin)
This is a bactericidal antibiotic that inhibits cell-wall synthesis. It is used to treat infections caused by penicillinase-producing staphylococci. Oxacillin may be used to start therapy when staphylococcal infection suspected.
Amoxicillin (Trimox, Moxatag)
Amoxicillin interferes with the synthesis of cell wall mucopeptides during active multiplication, resulting in bactericidal activity against susceptible bacteria. It is used as prophylactic therapy in in specific, high-risk patients.
Ceftriaxone (Rocephin)
This agent is an alternative to penicillin. It is a third-generation cephalosporin with broad-spectrum gram-negative activity. It has decreased efficacy against gram-positive organisms and increased efficacy against resistant organisms. It arrests bacterial growth by binding 1 or more penicillin-binding proteins. Antibiotics for endocarditis prophylaxis may be required for patients before performing procedures that are high risk for bacteremia. Ceftriaxone may be used prophylactically for high-risk patients undergoing dental procedures.
Cephalexin (Keflex)
Cephalexin is a first-generation cephalosporin that inhibits bacterial replication by inhibiting bacterial cell wall synthesis. It is bactericidal and effective against rapidly growing organisms forming cell walls. It is effective for treatment of infections caused by streptococci or staphylococci, including penicillinase-producing staphylococci. Cephalexin may be used prophylactically for high-risk patients undergoing dental procedures.
Gentamicin (Garamycin)
Gentamicin is an aminoglycoside antibiotic for gram-negative coverage. It is not the drug of choice, but consider using it if penicillins or other, less toxic drugs are contraindicated; if it is clinically indicated; or if mixed infections are caused by susceptible staphylococci and gram-negative organisms.
Dosing regimens for gentamicin are numerous; adjust the dose on the basis of creatinine clearance and changes in the volume of distribution. Follow up each regimen by measuring the trough level drawn 30 min before the third or fourth dose. Peak levels may be drawn 30 min after a 30-min infusion.
Vancomycin (Vancocin)
This is the drug of choice in patients who cannot receive or whose condition fails to respond to penicillins and cephalosporins or who have infections with resistant staphylococci. Vancomycin is a potent antibiotic that is directed against gram-positive organisms and is active against Enterococcus species. MRSA infection on native valves is treated with vancomycin for at least 6 weeks, with or without 3-5 days of gentamicin. To avoid toxicity, the current recommendation is to assay trough levels 0.5 hour before the fourth dose. In renal impairment, adjust the dose according to creatinine clearance.
Cefazolin
Cefazolin is a first-generation semisynthetic cephalosporin, which by binding to 1 or more penicillin-binding proteins, arrests bacterial cell wall synthesis and inhibits bacterial replication. In patients with penicillin allergies, cefazolin may be used for antibiotic prophylaxis for high-risk patients undergoing dental procedures.
Clindamycin (Cleocin, Cleocin Pediatric, Clindamax)
Clindamycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It distributes widely in the body, without penetration of the CNS. It is used in penicillin-allergic patients undergoing dental, oral, or respiratory tract procedures. It is useful for treatment against streptococcal and most staphylococcal infections. Clindamycin may be used prophylactically for high-risk patients undergoing dental procedures.
Azithromycin
Azithromycin is a macrolide antibiotic that acts by binding to the 50S ribosomal subunit of susceptible microorganisms and blocks the dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Azithromycin may be used prophylactically for high-risk patients undergoing dental procedures in patients who are penicillin allergic.
Rifampin
Rifampin inhibits RNA synthesis in bacteria by binding to the beta subunit of DNA-dependent RNA polymerase, which, in turn, blocks RNA transcription. Bacterial endocarditis with an MSSA infection on prosthetic tissue is treated with nafcillin or oxacillin plus rifampin for at least 6 weeks, in combination with gentamicin for 2 weeks. MRSA infection on prosthetic tissue is treated with vancomycin plus rifampin for at least 6 weeks, in combination with gentamicin for 2 weeks.
Amphotericin B (Amphocil, Fungizone)
Amphotericin B is produced by a strain of Streptomyces nodosus; it can be fungistatic or fungicidal. This agent binds to sterols (eg, ergosterol) in the fungal cell membrane, causing intracellular components to leak, with subsequent cell death. Amphotericin B may be effective in the treatment of fungal endocarditis.
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Pediatric Bacterial Endocarditis. A young adult with a history of intravenous drug use diagnosed with right-sided staphylococcal endocarditis and multiple embolic pyogenic abscesses on chest radiograph.
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Pediatric Bacterial Endocarditis. Long axis echocardiographic view demonstrating a vegetation (Veg) on the aortic (Ao) valve. LA, left atrium; LV, left ventricle.
