The HACEK group includes weakly virulent, gram-negative organisms that primarily cause endocarditis.

The HACEK group of nonmotile, gram-negative bacilli or coccobacilli contains a number of minimally pathogenic, slow-growing, fastidious genera. Their primary pathology is endocarditis in susceptible people; about 1% of endocarditis cases are due to this group. The group consists of

• Haemophilus sp, which may cause respiratory infections or, less commonly, endocarditis
• Actinobacillus actinomycetemcomitans, which usually occurs with A. israelii in actinomycosis (see Anaerobic Bacteria: Actinomycosis)
• Cardiobacterium hominis
• Eikenella corrodens, which usually occurs in human bite wounds, endocarditis, brain and visceral abscesses, osteomyelitis, respiratory infections, uterine infections related to intrauterine devices, and mixed soft-tissue infections
• Kingella kingae

Antibiotic sensitivities differ among species, so treatment should be directed by susceptibility testing.

Last full review/revision August 2009 by Burke A. Cunha, MD

Content last modified February 2012