Invited Commentary

Abstract

The term culture-negative endocarditis is an enigma. It is our inability to identify the causative organism. The article by Polat and colleagues [1Polat A. Tuncer A. Tuncer E.Y. et al.Surgical treatment of culture-negative aortic infective endocarditis.Ann Thorac Surg. 2012; (93:44–50)Google Scholar] highlights this problem and also refers to the reasons for not identifying the organism. However it is disturbing to note that nearly half of their patients had culture-negative endocarditis. Culture-negative endocarditis is a term that describes a situation in which the diagnosis of endocarditis according to Duke's criteria is not in doubt, but the causative organism is unidentified. There are several reasons for this unusual occurrence: (1) prior use of antibiotics is a major cause and as physicians we tend to overprescribe them; (2) slow-growing or attenuated organisms or nonbacterial species (fungus/virus) causing endocarditis; (3) endocarditis caused by unusual organisms such as Chlamydia, Legionella, Bartonella, and Aspergillus species; (4) unsatisfactory bacteriologic examination in which some laboratories fail to grow organisms; and finally (5) unsatisfactory examination of surgical /autopsy specimens (eg, pus from abscess, vegetations, valve cusp/tissue).With improvement in bacteriologic and serologic examination, one can expect to bring down the incidence of culture-negative endocarditis to around 20%. It is important to identify the organism carefully with meticulous examination. Treating patients with broad-spectrum antibiotics blindly for 6 weeks or longer—with a higher risk of recurrence, mortality, and morbidity—is best avoided. Aortic valve endocarditis gives the surgeon several options. One may repair or replace with a homograft, autograft, or mechanical valve. In the elderly, a tissue valve option is available. The choice of procedure will be based entirely on the availability of a tissue bank, experience of the surgeon, and age of the patient. A homograft or autograft is perhaps the best option to reconstruct an extensively destroyed aortic root in young patients, especially those with prosthetic valve endocarditis. A large number of additional procedures, especially of the mitral valve, may complicate the surgical procedure. The article by Polat and colleagues highlights many of these problems, including the high mortality rate when treating an invisible, invincible, and formidable enemy. The term culture-negative endocarditis is an enigma. It is our inability to identify the causative organism. The article by Polat and colleagues [1Polat A. Tuncer A. Tuncer E.Y. et al.Surgical treatment of culture-negative aortic infective endocarditis.Ann Thorac Surg. 2012; (93:44–50)Google Scholar] highlights this problem and also refers to the reasons for not identifying the organism. However it is disturbing to note that nearly half of their patients had culture-negative endocarditis. Culture-negative endocarditis is a term that describes a situation in which the diagnosis of endocarditis according to Duke's criteria is not in doubt, but the causative organism is unidentified. There are several reasons for this unusual occurrence: (1) prior use of antibiotics is a major cause and as physicians we tend to overprescribe them; (2) slow-growing or attenuated organisms or nonbacterial species (fungus/virus) causing endocarditis; (3) endocarditis caused by unusual organisms such as Chlamydia, Legionella, Bartonella, and Aspergillus species; (4) unsatisfactory bacteriologic examination in which some laboratories fail to grow organisms; and finally (5) unsatisfactory examination of surgical /autopsy specimens (eg, pus from abscess, vegetations, valve cusp/tissue). With improvement in bacteriologic and serologic examination, one can expect to bring down the incidence of culture-negative endocarditis to around 20%. It is important to identify the organism carefully with meticulous examination. Treating patients with broad-spectrum antibiotics blindly for 6 weeks or longer—with a higher risk of recurrence, mortality, and morbidity—is best avoided. Aortic valve endocarditis gives the surgeon several options. One may repair or replace with a homograft, autograft, or mechanical valve. In the elderly, a tissue valve option is available. The choice of procedure will be based entirely on the availability of a tissue bank, experience of the surgeon, and age of the patient. A homograft or autograft is perhaps the best option to reconstruct an extensively destroyed aortic root in young patients, especially those with prosthetic valve endocarditis. A large number of additional procedures, especially of the mitral valve, may complicate the surgical procedure. The article by Polat and colleagues highlights many of these problems, including the high mortality rate when treating an invisible, invincible, and formidable enemy.