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HACEK Infections

By Larry M. Bush, MD, Maria T. Perez, MD

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 5% of endocarditis cases are due to this group, making them the most common causes of gram-negative bacilli endocarditis. The group consists of

  • Haemophilus sp ( H. parainfluenza, H. aphrophilus, and H. paraphrophilus), which may cause respiratory infections or, less commonly, endocarditis

  • Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans, which usually occurs with A. israelii in actinomycosis (see Actinomycosis)

  • Cardiobacterium hominis

  • Eikenella corrodens, which usually occurs in human bite wounds, endocarditis (often in IV drug users), brain and visceral abscesses, osteomyelitis, respiratory infections (including empyemas), 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. However, increasing β-lactam resistance has made ceftriaxone and ampicillin/sulbactam the current antibiotics of choice.

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