ANTIMICROBIAL THERAPY
Antimicrobial therapy must be bactericidal and prolonged. See Table 87-2 for organism-specific regimens. Most pts defervesce within 5-7 days. Blood cultures should be repeated until sterile, and results should be rechecked if there is recrudescent fever and at 4-6 weeks after therapy to document cure. If pts are febrile for 7 days despite antibiotic therapy, an evaluation for paravalvular or extracardiac abscesses should be performed.

• Pts with acute endocarditis require antibiotic treatment as soon as three sets of blood culture samples are obtained, but stable pts with subacute disease should have antibiotics withheld until a diagnosis is made. Pts treated with vancomycin or an aminoglycoside should have serum drug levels monitored. Tests to detect renal, hepatic, and/or hematologic toxicity should be performed periodically.
• Selection of optimal treatment for streptococcal endocarditis requires determination of the minimal inhibitory concentration (MIC) of penicillin for the causative isolate. Two-week regimens should not be used for complicated NVE or for PVE. Groups B, C, and G streptococcal endocarditis should be treated with the regimen recommended for relatively penicillin-resistant streptococci (Table 87-2).
• Enterococci require the synergistic activity of a cell wall-active agent and an aminoglycoside for killing. Enterococci must be tested for high-level resistance to streptomycin and gentamicin; if resistance is detected, the addition of an aminoglycoside will not produce a synergistic effect, and the cell wall-active agent should be given alone for periods of 8-12 weeks or-for Enterococcus faecalis-high-dose ampicillin plus ceftriaxone can be given. If treatment fails or the isolate is resistant to commonly used agents, surgical therapy is advised (see below and Table 87-3). The aminoglycoside can be discontinued in those pts who have responded satisfactorily to therapy if toxicity develops after 2-3 weeks of treatment.
• Staphylococcal PVE is treated for 6-8 weeks with a multidrug regimen. Rifampin is important because it kills organisms adherent to foreign material. Two other agents in addition to rifampin help prevent the emergence of rifampin resistance in vivo. Susceptibility testing for gentamicin should be performed before rifampin is given; if the strain is resistant, another aminoglycoside or a fluoroquinolone should be substituted.
• Pts with negative blood cultures and without confounding prior antibiotic treatment should receive ceftriaxone plus gentamicin. If the pt has a prosthetic valve, those two drugs plus vancomycin should be given.

SURGICAL TREATMENT
Surgery should be considered early in the course of illness in pts with the indications listed in Table 87-3, although most of these indications are not absolute. However, pts who develop acute aortic regurgitation with preclosure of the mitral valve or a sinus of Valsalva abscess rupture into the right heart require emergent surgery. Likewise, surgery should not be delayed when severe valvular dysfunction with progressive CHF or uncontrolled or perivalvular infection is present. Cardiac surgery should be delayed for 2-3 weeks if possible when the pt has had a nonhemorrhagic embolic stroke and for 4 weeks when the pt has had a hemorrhagic embolic stroke. Ruptured mycotic aneurysms should be clipped and cerebral edema allowed to resolve prior to cardiac surgery.

ANTIBIOTIC THERAPY AFTER CARDIAC SURGERY

• Uncomplicated NVE caused by susceptible organisms, with negative valve cultures at surgery: The duration of pre- and postoperative treatment should equal the total duration of recommended therapy, with ~2 weeks of treatment given postoperatively.
• Endocarditis with paravalvular abscess, partially treated PVE, or culture-positive valves: Pts should receive a full course of therapy postoperatively.