Laribacter hongkongensis gen. nov., sp nov., a novel gram-negative bacterium isolated from a cirrhotic patient with bacteremia and empyema

A bacterium was isolated from the blood and empyema of a cirrhotic patient. The cells were facultatively anaerobic, nonsporulating, gram-negative, sea gull shaped or spiral rods. The bacterium grows on sheep blood agar as nonh emolytic, gray colonies I mm in diameter after 24 h of incubation at 37 deg reesC in ambient air. Growth also occurs on MacConkey agar and at 25 and 42 degreesC but not at 4, 44, and 50 degreesC. The bacterium can grow in 1 or 2% but not 3, 4, or 5% NaCl. No enhancement of growth is observed with 5% CO2. The organism is aflagellated and nonmotile at both 25 and 37 degreesC. It is oxidase, catalase, urease, and arginine dihydrolase positive, and it reduces nitrate. It does not ferment, oxidize, or assimilate any sugar tes ted. 16S rRNA gene sequencing showed that there are 91 base differences (6. 2%), 112 base differences (7.7%), and 116 base differences (8.2%) between t he bacterium and Microvirgula aerodenitrificans, Vogesella indigofera, and Chromobacterium species, respectively. The G+C content (mean and standard d eviation) is 68.0% +/- 2.43%, and the genomic size is about 3 Mb. Based on phylogenetic affiliation, the bacterium belongs to the Neisseriaceae family of the beta -subclass of Proteobacteria. For these reasons, a new genus an d species, Laribacter hongkongensis gen. nov., sp. nov., is proposed, for w hich HKU1 is the type strain. Further studies should be performed to ascert ain the potential of this bacterium to become an emerging pathogen.