choice of antibiotic

Last reviewed 01/2018

Treatment of infective endocarditis (IE) should be tailored to in-vitro susceptibility of the pathogen identified, and consultation with an infectious disease specialist can be considered (1, 2). In general, antibiotics such as penicillin, ampicillin, ceftriaxone, rifampin, vancomycin and daptomycin are used

  • length of treatment is dependent on the pathogen and type of valve (native vs. prosthetic)
    • viridans group streptococci endocarditis should be treated for 4 weeks for native valve IE and 6 weeks for prosthetic valve IE
    • for the more virulent staphylococcus aureus, treatment duration is 6 weeks, regardless of valve type. However, prosthetic valves require the addition of rifampin or gentamicin for synergy
    • enterococcus endocarditis requires combination antimicrobial therapy for 4-6 weeks, regardless of valve type
    • generally, ampicillin is used in combination with either gentamicin or ceftriaxone, depending on the patient's renal function
    • treatment duration for the HACEK organisms (Hemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella) is 4 weeks for native valves and 6 weeks for prosthetic valves.

Some examples are possible treatment regimes are detailed below:

  • blind therapy
    • intravenous benzylpenicillin and gentamicin unless staphylococcal suspected when vancomycin is substituted for penicillin
    • if patient is penicillin allergic then vancomycin and gentamicin

  • streptococci e.g. Strep. viridans
    • if uncomplicated and fully penicillin-sensitive viridans or S.bovis involving native valve then iv benzylpenicillin plus iv gentamicin for 2 weeks usually sufficient for cure (1); however, if not fully penicillin-sensitive or evidence of cardiac or embolic complications then treat for 4 weeks with benzylpenicillin, with gentamicin for first 2 weeks
    • if infection involves a prosthetic valve then penicillin should be continued for 6 weeks with gentamicin for first 2 weeks

  • enterococci e.g. Enterococcus faecalis
    • iv amoxicillin plus gentamicin for 4-6 weeks (1)
    • 25% of isolates gentamicin resistant and some respond to streptomycin plus amoxicillin; some organisms have high-level resistance to gentamicin and streptomycin and may respond to prolonged treatment with high-dose amoxicillin, but surgery to replace the infected valve is often necessary (1)

  • staphylococci e.g. Staph. aureus, Staph epididermis
    • for suspected staphylococcal endocarditis then iv vancomycin plus iv gentamicin
    • treat for 6 weeks; stop gentamicin after 1 week (1)
    • if a meticillin-sensitive staphylococcus is isolated then treatment can be changed to flucloxacillin for 6 weeks plus gentamicin for up to 1 week; if isolate is sensitive to penicillin (rare nowadays) then benzylpenicillin should be used instead of flucloxacillin
    • if a prosthetic valve then some recommend treatment for 6 weeks with vancomycin or flucloxacillin plus gentamicin for first 2 weeks (1)

  • Patients who are allergic to penicillin should not be given the above combinations of drugs, flucloxacillin or cephalosporins. Vancomycin is recommended in these patients

Notes:

  • these suggested regimes are merely illustrative of possible treatment options; prescribers must check drugs and their doses in the current issue of BNF. Also prescribers must check with local microbiological guidelines for antibiotic regimes to be used in infective endocarditis

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