What causes culture-negative infective endocarditis (IE)?

Updated: Jan 03, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Approximately 5% of cases of possible IE yield negative blood culture results (ie, culture-negative IE). Patients with culture-negative IE occasionally present with signs and symptoms highly suggestive of IE, but the blood cultures remain negative.

Culture-negative IE may have noninfectious causes (eg, vasculitis) or may be caused by fastidious organisms. Modern blood culture systems recover the vast majority of pathogens within 4-5 days, including members of the HACEK group and Abiotrophia species. Overall, the most common cause of culture-negative IE is prior antimicrobial therapy that can suppress bacterial growth within the vegetation but is insufficient to eliminate the valvular infection.

In certain populations, infections with Coxiella burnetii (in southern France and Israel) and Bartonella species (among homeless persons) have become more frequent causes of culture-negative IE. The blood culture results in fungal valvular infections are often sterile. In S aureus IE, the blood cultures results may be negative when the organism burrows deep within the thrombus, leaving the surface of the valvular thrombus sterile (surface sterilization). [63]

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