[Aminoglycosides in the treatment of infectious endocarditis]

The role of aminoglycosides in the treatment of infective endocarditis is well established. The combination of a beta-lactam with an aminoglycoside shortens the treatment of endocarditis due to penicillin-sensitive streptococci (MIC < or = 0.1 micrograms/mL) when compared to beta-lactams alone. Patients at higher risk (e.g. with prosthetic valves, clinical duration of symptoms > 3 months) should be treated with penicillin for 4 weeks in combination with an aminoglycoside for 2 weeks. Once-daily dosing (ODD) of aminoglycosides can be recommended in penicillin-sensitive streptococcal endocarditis. The treatment of endocarditis due to streptococci relatively and/or highly resistant to penicillin requires combined treatment with penicillin plus an aminoglycoside for a longer duration. At present ODD of aminoglycosides cannot be recommended. Enterococcal endocarditis requires combined treatment for 4 to 6 weeks. Based upon experimental data, ODD of aminoglycosides appears to be markedly inferior to q 8 h dosing. Enterococcal isolates should be screened for high-level resistance to streptomycin and gentamicin. Gentamicin is the preferred agent if susceptibility testing is not performed. Aminoglycosides are administered during the initial 3 to 5 days of treatment for staphylococcal endocarditis on native valves in order to shorten the duration of bacteremia. For staphylococcal prosthetic valve endocarditis, aminoglycosides are administered for the initial 2 weeks of treatment. However, there are no reliable clinical data for methicillin-susceptible isolates to support this recommendation. In prosthetic valve endocarditis due to coagulase-negative staphylococci combination with an aminoglycoside appears to suppress the emergence of rifampin-resistant variants during treatment. There are no data on ODD of aminoglycosides in staphylococcal endocarditis. Right-sided staphylococcal endocarditis due to methicillin-susceptible staphylococci is adequately treated with a two-week course of a beta-lactam plus an aminoglycoside. This short regimen can be recommended for low risk patients, e.g. those without significant heart failure and vegetations < 2 cm3 and with an aminoglycoside-susceptible isolate.