[1] HACEK is an abbreviation of the initials of the genera of this group of bacteria: Haemophilus, Aggregatibacter (previously Actinobacillus), Cardiobacterium, Eikenella, Kingella.
[1] The HACEK organisms are a normal part of the human microbiota, living in the oral-pharyngeal region.
[2] The bacteria were originally grouped because they were thought to be a significant cause of infective endocarditis, but recent research has shown that they are rare and only responsible for 1.4–3.0% of all cases of this disease.
Culture-negative refers to an inability to produce a colony on regular agar plates because these bacteria are fastidious (require a specific nutrient).
The treatment of choice for HACEK organisms in endocarditis is the third-generation cephalosporin and β-Lactam antibiotic ceftriaxone.