RESUMO
Six species and six additional genovars are combined within the so-called Enterobacter cloacae complex, with one of them being the species Enterobacter hormaechei. In a recent population genetic study, two genetic clusters were found in close phylogenetic proximity to the genetic cluster of E. hormaechei. In order to prove the hypothesis that these three genetic clusters belong to the same species, we performed cross-hybridization experiments in microplates with DNAs of representatives of each genetic cluster. The close phylogenetic relationship among the clusters was reflected by their relatively low deltaT(m) values, ranging from 0.3 to 4.8, confirming the hypothesis that the clusters are parts of the same species. These clusters can be distinguished from the other species of the E. cloacae complex, which have deltaT(m) values of 5.6 to 10.3. Forty-eight E. hormaechei strains from the different genetic clusters were phenotypically characterized with 129 biochemical tests. In this way, E. hormaechei could be differentiated from the other species of the E. cloacae complex because it tests negative in the 3-hydroxy-butyrate test. The three genetic clusters of E. hormaechei could also be differentiated from each other by using phenotypic tests. Hence, we propose three new subspecies of E. hormaechei corresponding to genetic clusters VI, VII, and VIII of the E. cloacae complex. E. hormaechei subsp. hormaechei comb. nov. corresponds to the original species description, as it gives negative results for the adonitol, d-arabitol, d-sorbitol, and d-melibiose tests and a positive result for the dulcitol test. E. hormaechei subsp. oharae subsp. nov. gives negative results for the dulcitol, adonitol, and d-arabitol tests and positive results for the d-sorbitol and d-melibiose tests. E. hormaechei subsp. steigerwaltii subsp. nov. gives a negative result for the dulcitol test and positive results for the adonitol, d-arabitol, d-sorbitol, and d-melibiose tests. Among the members of the E. cloacae complex, E. hormaechei seems to be the species most frequently recovered from clinical specimens.
Assuntos
Enterobacter/classificação , Infecções por Enterobacteriaceae/microbiologia , Técnicas de Tipagem Bacteriana , Chaperonina 60/genética , Pré-Escolar , DNA Bacteriano/análise , DNA Ribossômico/análise , Enterobacter/genética , Enterobacter/isolamento & purificação , Humanos , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Fenótipo , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
The taxonomic position of Enterobacter dissolvens was re-evaluated based on the analysis of the type strain ATCC 23373T and three clinical isolates. The strains were assigned to the genetic cluster of the species by phylogenetic sequence analysis in the frame of a recent population genetic study. The relatedness of E. dissolves to the other species of the E. cloacae complex was analyzed by DNA-DNA hybridization studies based on melting profiles in microplates. The genetic cluster of E. dissolvens fell into the same DNA-relatedness group like E. cloacae with mean deltaTm-values of 3.9 degrees C confirming the hybridization results of three former studies. Phenotypic analysis of the E. cloacae and E. dissolvens strains, respectively, based on 115 biochemical reactions yielded the esculin test as the only one differentiating between them by being positive for E. dissolvens and negative for E. cloacae strains. The name E. cloacae subsp. dissolvens comb. nov. is proposed for the group of organisms formerly referred to as E. dissolvens, and the name E. cloacae subsp. cloacae comb. nov. for the group of organisms formerly referred to as E. cloacae. The species descriptions of Enterobacter kobei and Enterobacter asburiae were emended based on the data collected on 17 and 15 strains, respectively. The strains were assigned to the respective species by a combination of phylogenetic sequence analyzes and DNA-DNA hybridizations. Phenotypic analyzes of 115 reactions gave detailed species profiles with new differentiating phenotypic properties.
Assuntos
DNA Bacteriano/genética , Enterobacter/classificação , Hibridização de Ácido Nucleico , Técnicas de Tipagem Bacteriana , DNA Bacteriano/química , DNA Ribossômico/química , Enterobacter/fisiologia , Esculina/metabolismo , Genes de RNAr , Dados de Sequência Molecular , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Temperatura de TransiçãoRESUMO
A new species, Enterobacter ludwigii, is presented on the basis of the characteristics of 16 strains, which were isolated from clinical specimens. These bacteria form a distinct genetic cluster in phylogenetic analyses of the population structure of the Enterobacter cloacae complex. As determined by DNA-DNA cross-hybridization experiments in microplates, this genetic cluster can be delineated from the other species of the E. cloacae complex with deltaTm values equal to or above 5 degrees C with Enterobacter hormaechei being the closest relative. The bacteria are gram-negative, fermentative, motile rods with the general characteristics of the genus Enterobacter and the E. cloacae complex in particular. E. ludwigii can be differentiated from the other Enterobacter species by its growth on myo-inositol and 3-0-methyl-D-glucopyranose. The type strain is EN-119 (= DSM 16688T = CIP 108491T).
