Aortic valve endocarditis possibly caused by a Haematobacter-like species

Haematobacter is a newly proposed genus for a group of fastidious Gram-negative aerobic bacilli isolated mostly from blood samples from patients with septicemia. The Haematobacter genus currently includes two species, H. massiliensis and H. missouriensis. We report isolation of a novel Haematobacter-like species from the blood of a 65-year-old man who suffered from probable aortic valve endocarditis. The possible causative role was suggested by the monomicrobial culture and the absence of another causative agent in a patient with probable endocarditis by Duke criteria. This fastidious organism could not be identified by routine biochemical tests. Sequencing analysis of the 16S rRNA gene (1,425 bp) best matched the known Haematobacter species yet was substantially different with a nucleotide similarity of 96.7%. This strain also reduced nitrate to nitrite, unlike known species. This case is likely the first reported case of endocarditis possibly caused by a Haematobacter-like organism.