Description of Wautersiella falsenii gen. nov., sp. nov., to accommodate clinical isolates phenotypically resembling members of the genera Chryseobacterium and Empedobacter

Abstract

A total of 26 isolates of non-fermenting, Gram-negative rods, obtained between 1980 and 2004 by various clinical laboratories in Belgium, with phenotypic characteristics resembling those of members of the genera Chryseobacterium and Empedobacter (indole-positive) and a biochemical profile resembling that of CDC group II-h, but urease-positive, were collected at the Université Catholique de Louvain Microbiology Laboratory, Belgium. The 16S rRNA gene sequences were determined for most of the isolates and showed 94–95 % similarity with the type strain of Empedobacter brevis as the closest relative, indicating that these isolates might belong to a separate genus. Furthermore, the 16S rRNA gene sequences of the isolates were similar, but two clusters (genomovars) could be distinguished. The sequence similarities were 99.5–100 % for the 14 isolates of genomovar 1 and 99.4–100 % for the 12 isolates of genomovar 2. The similarity between the two clusters was 98.3–99.5 %. The presence of two clearly different groups was corroborated by using tRNA intergenic length polymorphism analysis, which also enabled differentiation of the novel species from all other species studied thus far using this technique. DNA–DNA hybridization results excluded a close relatedness to Empedobacter brevis. The DNA G+C contents of the reference strains of genomovars 1 and 2 were 33.8±0.4 and 34.4±0.2 mol%, respectively. The name Wautersiella falsenii gen. nov., sp. nov., is proposed for this group, comprising two closely related genomovars. The type strain of the species and reference strain for genomovar 1 is NF 993T (=CCUG 51536T=CIP 108861T), which was isolated from a surgical wound. The reference strain for genomovar 2 is NF 770 (=CCUG 51537=CIP 108860), which was isolated from blood.