Description of Francisella hispaniensis sp. nov., isolated from human blood, reclassification of Francisella novicida (Larson et al. 1955) Olsufiev et al. 1959 as Francisella tularensis subsp. novicida comb. nov. and emended description of the genus Francisella

Abstract

Strain FhSp1T, isolated from human blood in Spain in 2003, was studied for its taxonomic allocation. By 16S rRNA and recA gene sequencing, the strain was shown to belong to the genus Francisella. In the 16S rRNA gene sequence, Francisella sp. FhSp1T shared similarity of more than 99 % with strains of Francisella tularensis subspecies and Francisella novicida U112T, 98 % with Francisella piscicida GM2212T and 98.4 % with Francisella philomiragia ATCC 25015T. In the recA gene sequence, Francisella sp. FhSp1T exhibited 91.6–91.7 % similarity to strains of F. tularensis subspecies, 91.2 % to F. novicida U112T and 84 % to F. philomiragia ATCC 25017. The genus affiliation was supported by a quinone system typical of Francisella (Q-8 as the major component), a complex polar lipid profile similar to that of F. tularensis with the major components diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unknown aminophospholipid (APL4) and a fatty acid profile consisting mainly of C10 : 0 (17.2 %), C14 : 0 (11.2 %), C16 : 0 (13.1 %), C18 : 0 3-OH (14.2 %) and C18 : 1 ω9c (7.1 %). DNA–DNA hybridization, which showed unambiguously that FhSp1T represents a novel species, and the results of biochemical tests allowed genotypic and phenotypic differentiation of the isolate from all hitherto-described Francisella species. A multiplex PCR developed in the course of this study discriminated FhSp1T from representatives of all other Francisella species and subspecies, clades A.I and A.II of F. tularensis subsp. tularensis and F. tularensis subsp. holarctica biovar japonica and also between these representatives of the genus. Therefore, we propose the name Francisella hispaniensis sp. nov., with the type strain FhSp1T (=FnSp1T =FSC454T =F62T =DSM 22475T =CCUG 58020T). Furthermore, we formally propose the transfer of the species Francisella novicida to the species Francisella tularensis as Francisella tularensis subsp. novicida comb. nov. (type strain ATCC 15482T =CCUG 33449T =CIP 56.12T). We also present an emended description of the genus Francisella.