- Infective endocarditis is an uncommon infection usually occurring in persons with preexisting cardiac valvular abnormalities (e.g., prosthetic heart valves) or with other specific risk factors (e.g., IV drug abuse).
- Three groups of organisms cause a majority of infective endocarditis cases: streptococci, staphylococci, and enterococci.
- The clinical presentation of infective endocarditis is highly variable and nonspecific, although a fever and murmur are usually present. Classic peripheral manifestations (e.g., Osler’s nodes) may or may not occur.
- The diagnosis of infective endocarditis requires the integration of clinical, laboratory, and echocardiographic findings. The two major diagnostic criteria are bacteremia and echocardiographic changes (e.g., valvular vegetation).
- Treatment of infective endocarditis involves isolation of the infecting pathogen and determination of antimicrobial susceptibilities, followed by high-dose, parenteral, bactericidal antibiotics for an extended period.
- Surgical replacement of the infected heart valve is an important adjunct to endocarditis treatment in certain situations (e.g., patients with acute heart failure).
- β-Lactam antibiotics, such as penicillin G (or ceftriaxone), nafcillin, and ampicillin, remain the drugs of choice for streptococcal, staphylococcal, and enterococcal endocarditis, respectively.
- Aminoglycoside antibiotics are essential to obtain a synergistic bactericidal effect in the treatment of enterococcal endocarditis. Adjunctive aminoglycosides also may decrease the emergence of resistant organisms (e.g., prosthetic valve endocarditis caused by coagulase-negative staphylococci) and hasten the pace of clinical and microbiologic response (e.g., some streptococcal and staphylococcal infections).
- Vancomycin is reserved for patients with immediate β-lactam allergies and the treatment of resistant organisms.
- Antimicrobial prophylaxis is used as an attempt to prevent infective endocarditis for patients who are at the highest risk (such as persons with prosthetic heart valves) before a bacteremia-causing procedure (e.g., dental extraction).
Upon completion of the chapter, the reader will be able to:
List patient populations at increased risk for developing infective endocarditis (IE).
Delineate bacteria that commonly cause IE as well as situations where certain bacteria are more likely.
Describe the sequential steps necessary to develop hematogenous spread of IE.
Identify the clinical manifestations of the disease, including physical findings, laboratory abnormalities, blood cultures, and other diagnostic test (e.g., echocardiography).
Argue the importance of correctly obtained blood cultures and state situations that may lead to “culture-negative” IE.
Justify the rationale for high-dose parenteral, bactericidal, extended-duration antibiotics for IE treatment.
Summarize the role of nonpharmacologic approaches (i.e., surgery) in the treatment of IE and identify situations where this approach is preferred.
Design drug regimens for the following types of infective endocarditis: streptococci, staphylococci, enterococci, the HACEK microorganisms, and “culture-negative” IE.
Describe why β-lactam antibiotics are preferred for the treatment of IE and classify situations where vancomycin is appropriate.
Evaluate the role of penicillin skin tests in patients with a documented penicillin allergy.
Distinguish situations where aminoglycosides (i.e., gentamicin) should and should not be used for the treatment of IE and develop an appropriate dosing strategy based on the identified organism.
Summarize approaches that can be used to ensure cost-effective IE treatment, including methods to identify candidates for home health care.