Identification of “ Haematobacter ,” a New Genus of Aerobic Gram-Negative Rods Isolated from Clinical Specimens, and Reclassification of Rhodobacter massiliensis as “ Haematobacter massiliensis comb. nov.”

Abstract

ABSTRACT Twelve strains of gram-negative, nonfermenting rods recovered mainly from septicemic patients were studied using conventional and molecular methods. The phenotypic profiles of these strains most closely resembled Psychrobacter phenylpyruvicus . They produced catalase, oxidase, urease, and H 2 S (lead acetate paper) but did not produce indole, reduce nitrate or nitrite, or hydrolyze gelatin or esculin. No acid production was observed in a King's oxidation-fermentation base containing d -glucose, d -xylose, d -mannitol, sucrose, lactose, or maltose. All strains were nonmotile and nonpigmented. Most strains produced green discoloration on blood agar. All strains grew at 25°C and 35°C and most grew on MacConkey agar. They shared a common cellular fatty acid (CFA) profile characterized by large amounts (56% to 90%) of 18:1ω7c and the presence of 3-OH-10:0, 16:1ω7c, 16:0, and 19:0cycω8c that overall was most similar to that of Rhodobacter species but was quite distinct from that of P. phenylpyruvicus . The MICs for most β-lactams, fluoroquinolones, aminoglycosides, and carbapenems were low. MICs for aztreonam and piperacillin were higher, with MICs for some strains of > 64 mg/liter and > 128 mg/liter, respectively. Polyphasic analysis of these strains, including morphological, biochemical, CFA composition, DNA-DNA hybridization, 16S rRNA gene sequencing, and percent guanine-plus-cytosine (G+C) content analysis, demonstrated that these strains and Rhodobacter massiliensis represent a new genus, “ Haematobacter ” (proposed name), with the species H. missouriensis (type strain H1892 T = CCUG 52307 T = CIP 109176 T ) and H. massiliensis comb. nov. (type strain Framboise T = CCUG 47968 T = CIP 107725 T ) and an unnamed genomospecies.