Update on blood culture-negative endocarditis

Blood culture-negative endocarditis is often severe, and difficult to diagnose. The rate of non-documented infective endocarditis has decreased with the advent of molecular biology improved performance for the diagnosis of bacterial endocarditis with blood cultures sterilized by previous antibacterial treatment and cardiac surgery access to the main infected focus, the endocardium, for half of the patients. Blood culture-negative endocarditis are classified in 3 main categories: (i) bacterial endocarditis with blood cultures sterilized by previous antibacterial treatment (usually due to usual endocarditis-causing bacteria, i.e. streptococci, more rarely staphylococci, or enterococci); (ii) endocarditis related to fastidious microorganisms (e.g. HACEK bacteria; defective streptococci Gemella, Granulicatella, and Abiotrophia sp. - Propionibacterium acnes, Candida sp.): in these cases, prolonged incubation will allow identifying the causative pathogen in a few days; (iii) and the true blood culture-negative endocarditis, due to intra-cellular bacteria that cannot be routinely cultured in blood with currently available techniques: in France. these are most frequently Bartonella sp., Coxiella burnetti (both easily diagnosed by ad hoc serological tests), and Tropheryma whipplei (usually diagnosed by PCR on excised cardiac valve tissue). Non-infective endocarditis is rare, mostly limited to marantic endocarditis, and the rare endocarditis related to systemic diseases (lupus, Behget). (C) 2014 Elsevier Masson SAS. All rights reserved.