This paper describes the discovery and characterization of a new bacterial genus, Cedecea, within the Enterobacteriaceae family. Seventeen strains were isolated from human clinical specimens in North America and analyzed using DNA-DNA hybridization and phenotypic testing. The genus name derives from CDC (Centers for Disease Control), where the organisms were originally identified. Two named species are proposed: Cedecea davisae (nine strains), the type species, and Cedecea lapagei (five strains), along with three unnamed strains. C. davisae ferments sucrose and D-xylose, requires thiamine for growth, and tests positive for ornithine decarboxylase and ascorbate. C. lapagei lacks these characteristics and grows on glucose without growth factor supplementation. DNA hybridization studies revealed five distinct DNA relatedness groups, with within-species homology of 80-100% but only 32-52% relatedness between the two named species and less than 23% relatedness to other Enterobacteriaceae. Phenotypically, Cedecea strains are gram-negative, peritrichous rods that produce lipase, are resistant to colistin and cephalothin, and negative for deoxyribonuclease and gelatin liquefaction. The clinical significance of these organisms remains unknown.

Key findings

• A new bacterial genus Cedecea was established within Enterobacteriaceae, comprising two validly named species (C. davisae and C. lapagei) plus three additional strains, all isolated from clinical sources
• DNA-DNA hybridization analysis showed five distinct DNA relatedness groups among 17 Cedecea strains, with within-species homology of 80-100% but less than 23% relatedness to other known Enterobacteriaceae genera
• C. davisae and C. lapagei can be differentiated by ornithine decarboxylase and ascorbate tests, acid production from sucrose and D-xylose, and thiamine requirement (present in C. davisae only)
• All Cedecea strains shared distinctive phenotypic characteristics: lipase positive, resistant to colistin and cephalothin, negative for deoxyribonuclease and gelatin liquefaction