Escherichia albertii sp. nov., a diarrhoeagenic species isolated from stool specimens of Bangladeshi children

Abstract

The taxonomic position of a group of five D-sorbitol- and lactose-negative enterobacterial isolates recovered from diarrhoeal stools of children at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), was investigated by DNA-DNA hybridization, phenotypic characterization and 16S rDNA sequencing. These strains were originally identified as 'Hafnia alvei-like' with the API 20E system but, in fact, show more phenotypic and genotypic resemblance to members of the genus Escherichia. By 16S rDNA sequencing, one representative strain of the ICDDR,B group was shown to be closely affiliated to the genera Escherichia and Shigella. Using the fluorimetric microplate hybridization method, the diarrhoeagenic ICDDR,B isolates were found to constitute a homogeneous taxon (> or = 82% internal DNA relatedness), with the closest affiliation to the type strains of Escherichia coli (55-64%) and Shigella flexneri (54-60%). The DNA-DNA hybridization levels were much lower with members of other described Escherichia species (16-45%) and with the type strain of H. alvei (9-17%). The G + C content of the ICDDR,B strains ranged from 50.5 to 50.7 mol%. Together with the diagnostic characteristics reported previously, including the presence of the eaeA gene of enteropathogenic E. coli and of the E. coli and Shigella-specific phoE gene, it is concluded that the ICDDR,B strains represent a novel taxon in the genus Escherichia, for which the name Escherichia albertii sp. nov. is proposed. Its type strain is Albert 19982(T) (= LMG 20976(T) = CCUG 46494(T)).