OBJECTIVES: Bacteria with common microbiological and clinical characteristics are often recognized as a particular group. The acronym HACEK stands for five fastidious genera associated with infective endocarditis. Data on the epidemiology of HACEK are sparse and therefore we report a six-year nationwide study of HACEK bacteraemia in Denmark.

METHODS: Cases of HACEK bacteraemia 2010 through 2015 were retrieved from the national Danish Microbiology Database covering an average surveillance population of 5.6 million per year.

RESULTS: We found 147 cases of HACEK bacteraemia corresponding to an annual incidence of 0.44 per 100,000 population. The annual incidence for males and females was 0.56 and 0.31 per 100,000, respectively. The median age was 56 years (range 0-97 years) with variation among genera. One hundred and forty-three isolates were identified to the species level and six to the genus level: Haemophilus spp. n=55, Aggregatibacter spp. n=37, Cardiobacterium spp. n=9, Eikenella corrodens n=21, and Kingella spp. n=27.

CONCLUSIONS: This is the first study of incidence of HACEK bacteraemia in a large surveillance population and may inspire further studies of the HACEK group. Haemophilus spp. other than Haemophilus influenzae accounted for most cases of HACEK bacteraemia in Denmark with Aggregatibacter spp. in second place.