INFECTIVE ENDOCARDITIS DUE TO UNUSUAL OR FASTIDIOUS MICROORGANISMS

Infective endocarditis due to fastidious microorganisms is-commonly en countered in clinical practice. Some organisms such as fungi account f or up to 15% of cases of prosthetic valve infective endocarditis, wher eas organisms of the HACEK group (Haemophilus parainfluenzae, H. aphro philus, and H. paraphrophilus, Actinobacillus actinomycetemcomitans, C ardiobacterium hominis, Eikenella corrodens, and Kingella kingae) caus e 3% of community-acquired cases of infective endocarditis. Special te chniques are necessary to identify these microorganisms. A history of contact with mammals or birds may suggest infection caused by Coxiella burnetii (Q fever), Brucella species, or Chlamydia psittaci, A nosoco mial cluster of postsurgical infective endocarditis may be caused by L egionella species or Mycobacterium species. If risk factors that are c ommonly associated with fungal infections (cardiac surgical treatment, prolonged hospitalization, indwelling central venous catheters, and l ong-term antibiotic use) are present, fungal endocarditis is possible. Patients with endocarditis and a history of periodontal disease or de ntal work in whom routine blood cultures are negative might have infec tion due to nutritionally variant streptococci or bacteria of the HACE K group. Communication between the microbiologist and the clinician is of crucial importance for identification of these microorganisms earl y during the course of the infection before complications such as embo lization or valvular failure occur. In this article, we review the mic robiologic and clinical features of these organisms and provide recomm endations for diagnosis and treatment.