HACEK organism

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Template:GCC

Overview

HACEK organisms is a group of fastidious, pleomorphic Gram negative bacilli which form part of the oropharynx commensals and account for about 3% of cases of endocarditis. They are slow growing and require enhanced carbon dioxide tension for recovery in culture. HACEK refers to the initials of organisms including:

• Haemophilus parainfluenzae, Aggregatibacter aphrophilus (formerly Haemophilus aphrophilus and Haemophilus paraphrophilus)

• Aggregatibacter actinomycetemcomitans (formerly Actinobacillus actinomycetemcomitans)

• Cardiobacterium hominis, Cardiobacterium valvarum

• Eikenella corrodens

• Kingella kingae, Kingella denitrificans

Pathophysiology

All of these organisms are part of the normal oropharyngeal flora which grow slowly, prefer a carbon dioxide–enriched atmosphere and share an enhanced capacity to produce endocardial infections, especially in young children.

In addition to valvular infections in the heart, these organisms can also produce other infections such as bacteremia, abscesses, peritonitis, otitis media, conjunctivitis, pneumonia, peritonitis, arthritis and osteomyelitis, and periodontal infections.

Epidemiology and Demographics

Collectivelly, they account for 5-10% of cases of infective endocarditis involving native valves and are the most common gram-negative cause of endocarditis among people who do not use IV drugs.

Diagnosis

Laboratory Studies

Because of their fastidious growth requirements, they have been a frequent cause of culture-negative endocarditis. Culture negative refers to its inability to produce a colony on regular agar plates, this is because they are fastidious (require a specific nutrient).

Treatment

The treatment of choice for HACEK organisms in endocarditis is ceftriaxone, a cephalosporin antibiotic. The dose is 2 g I.V. daily as a single dose for 4 weeks.

References

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