The HACEK group consists of fastidious, slow-growing, gram-negative bacteria whose growth requires carbon dioxide. Several Haemophilus spp., Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans, Aggregatibacter (formerly Haemophilus) aphrophilus, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae make up this group. Normal residents of the oral cavity, HACEK bacteria can cause both local oral infections and severe systemic disease, particularly endocarditis.