What are the treatment criteria for a patient suspected of having Infective Endocarditis (IE)?

From the Guidelines

The treatment of infective endocarditis (IE) requires prompt empiric antibiotic therapy followed by targeted treatment based on blood culture results, with consideration of the patient's clinical presentation, epidemiological factors, and potential complications, as outlined in the 2015 ESC guidelines 1. The initial choice of empirical treatment depends on several considerations, including whether the patient has received previous antibiotic therapy, the type of valve affected (native or prosthetic), and the place of infection (community, nosocomial, or non-nosocomial healthcare-associated IE) 1.

• For empiric therapy, a combination of vancomycin (15-20 mg/kg IV every 8-12 hours) plus ceftriaxone (2g IV daily) is recommended to cover both Staphylococcus aureus (including MRSA) and other common pathogens.
• Once the causative organism is identified through blood cultures, therapy should be narrowed to the most effective regimen, with consideration of the specific pathogen and its antibiotic susceptibility.
• For streptococcal IE, penicillin G (12-18 million units IV daily) or ceftriaxone (2g IV daily) for 4-6 weeks is typically used, while staphylococcal IE often requires nafcillin or oxacillin (2g IV every 4 hours) for methicillin-sensitive strains or vancomycin for resistant strains, usually for 6 weeks.
• Enterococcal IE typically requires combination therapy with ampicillin plus gentamicin, and treatment duration generally ranges from 4-6 weeks, with longer courses for prosthetic valve infections. Surgical intervention should be considered for complications such as heart failure, uncontrolled infection, or embolic events, as recommended in the 2014 AHA/ACC guideline 1. Patients require close monitoring with repeat blood cultures, echocardiography, and clinical assessment to ensure treatment efficacy, with consideration of repeat echocardiography if the initial images are negative and the diagnosis of IE is still being considered, as recommended in the 2015 AHA scientific statement 1. Early consultation with infectious disease and cardiology specialists is essential for optimal management of this serious condition, with consideration of the patient's individual needs and potential complications.

From the Research

Treatment Criteria for Infective Endocarditis (IE)

The treatment criteria for a patient suspected of having Infective Endocarditis (IE) involve several key considerations, including the identification of the causative organism, the selection of appropriate antimicrobial therapy, and the duration of treatment.

• The choice of antibacterial agent is dependent upon the susceptibility profile of the causative organism 2, 3.
• Patients with penicillin-sensitive viridans or nonenterococcal group D streptococcal endocarditis may be treated successfully with aqueous penicillin G alone for four weeks or with combined penicillin and streptomycin for two weeks 2.
• Enterococcal endocarditis should be treated for four to six weeks with a combination of aqueous penicillin G together with either streptomycin or gentamicin 2.
• Patients with endocarditis caused by Staphylococcus aureus should receive antimicrobial therapy for four to six weeks with a semisynthetic penicillin (nafcillin or oxacillin) or a cephalosporin such as cephalothin or cefazolin 2.
• In urgent cases where empiric antimicrobial therapy is necessary before the causative organism is identified, a combination of aqueous penicillin G, nafcillin, and gentamicin is effective therapy 2.

Diagnostic Considerations

• Isolating aetiological agents in patients with infective endocarditis remains problematical, and antibiotic exposure prior to blood cultures can result in culture-negative IE 4.
• Delaying antibiotic therapy for 72 hours in subacute presentations may improve the diagnostic yield 4.
• C-reactive protein (CRP) and rheumatoid factor (RF) can be useful in diagnosing IE, with CRP having a sensitivity of 97.0% and RF having a specificity of 93.8% 4.

Treatment Duration and Monitoring

• The duration of antibiotic treatment depends on the microorganism and whether there is a valvular prosthesis or not 5.
• Antibiotic treatment must be bactericidal, intravenously administered, and given for a long time to sterilize vegetations 5.
• Hospitalization is often mandatory, but there is a trend towards the use of outpatient treatments in some indications 5.
• The minimal inhibitory concentration (MIC) should be determined for all antibiotics used 6.