Incidence of HACEK bacteraemia in Denmark: A 6-year population-based study

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 (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella). Data on the epidemiology of HACEK are sparse. This article reports a 6-year nationwide study of HACEK bacteraemia in Denmark. Methods: Cases of HACEK bacteraemia occurring during the years 2010–2015 were retrieved from the national Danish microbiology database, covering an average surveillance population of 5.6 million per year. Results: A total of 147 cases of HACEK bacteraemia were identified, corresponding to an annual incidence of 0.44 per 100 000 population. The annual incidence for males was 0.56 per 100 000 and for females was 0.31 per 100 000. The median age was 56 years (range 0–97 years), with variation among the 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 on the incidence of HACEK bacteraemia in a large surveillance population and may inspire further studies on the HACEK group. Haemophilus spp other than Haemophilus influenzae accounted for most cases of HACEK bacteraemia in Denmark, with Aggregatibacter spp in second place.