HACEK

HACEK is an acronym that refers to a group of Gram-negative bacteria that are a notable cause of endocarditis, an infection of the inner lining of the heart. The acronym stands for Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella. These bacteria are part of the normal flora of the human oropharynx but can become pathogenic under certain conditions.

Members of the HACEK Group

Haemophilus

Haemophilus species are small, pleomorphic, Gram-negative coccobacilli. They are known for causing a variety of infections, including otitis media, sinusitis, and pneumonia. Haemophilus influenzae is the most well-known species within this genus.

Aggregatibacter

Aggregatibacter species, formerly classified under Actinobacillus, are Gram-negative coccobacilli. Aggregatibacter actinomycetemcomitans is a significant pathogen in periodontal disease and can also cause endocarditis.

Cardiobacterium

Cardiobacterium species are Gram-negative rods that are part of the normal flora of the human respiratory tract. Cardiobacterium hominis is the species most commonly associated with endocarditis.

Eikenella

Eikenella species, particularly Eikenella corrodens, are Gram-negative facultative anaerobes. They are known for causing infections in human bite wounds and can also be involved in endocarditis.

Kingella

Kingella species are Gram-negative coccobacilli. Kingella kingae is a notable pathogen in pediatric populations, causing septic arthritis and osteomyelitis.

Clinical Significance

The HACEK organisms are a rare but important cause of infective endocarditis, particularly in patients with pre-existing heart conditions. They are slow-growing and may require extended incubation periods for detection in blood cultures. Treatment typically involves prolonged courses of antibiotics, often guided by susceptibility testing.

Diagnosis

Diagnosis of HACEK-related infections involves blood cultures and molecular techniques such as polymerase chain reaction (PCR). Due to their fastidious nature, these organisms may not grow well on standard culture media, necessitating specialized laboratory techniques.

Treatment

Treatment of HACEK infections generally includes the use of beta-lactam antibiotics such as ceftriaxone or ampicillin. In cases of endocarditis, prolonged antibiotic therapy is often required, sometimes in combination with surgical intervention.

Related Pages

• Endocarditis
• Gram-negative bacteria
• Antibiotics
• Blood culture
• Polymerase chain reaction