Skip to Content

HACEK Infections


Larry M. Bush

, MD, FACP, Charles E. Schmidt College of Medicine, Florida Atlantic University;

Maria T. Vazquez-Pertejo

, MD, FACP, Wellington Regional Medical Center

Last full review/revision Feb 2020| Content last modified Feb 2020

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

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 species (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
  • 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 beta-lactam resistance has made ceftriaxone and ampicillin/sulbactam the current antibiotics of choice.

Drugs Mentioned In This Article

Drug Name Select Trade
ceftriaxone ROCEPHIN
ampicillin No US brand name

Copyright © 2022 Merck & Co., Inc., known as MSD outside of the US, Kenilworth, New Jersey, USA. All rights reserved. Merck Manual Disclaimer