Aeromonas hydrophila subsp. dhakensis subsp. nov., isolated from children with diarrhoea in Bangladesh, and extended description of Aeromonas hydrophila subsp. hydrophila (Chester 1901) Stanier 1943 (approved lists 1980).

A group of 10 Aeromonas hydrophila-like strains referred to as group BD-2, which mainly comprised haemolytic and cytotoxic isolates from diarrhoeal children in Bangladesh, was subjected to a polyphasic taxonomic study including fluorescent amplified fragment length polymorphism (FAFLP) and ERIC-PCR fingerprinting, microplate DNA-DNA hybridization and extensive phenotypic characterization. Comparison of FAFLP and ERIC-PCR genotypic profiles indicated that the group BD-2 isolates constituted a separate taxon that was most closely related to A. hydrophila DNA hybridization group (HG) 1. Determination of DNA-DNA hybridization values with type and reference strains of all known Aeromonas taxa revealed that the BD-2 group represented a homogeneous taxon (internal DNA homology, 77-94%) that exhibited 78-92% DNA relatedness with the type strain of A. hydrophila HG1. These results indicated that the BD-2 group belongs genotypically to A. hydrophila HG1, but examination of 152 phenotypic characteristics revealed that the group BD-2 isolates differed from representatives of HG1 in eight biochemical properties. The diagnostic value of at least three of these tests, namely utilization of urocanic acid and L-arabinose and acid production from L-arabinose, has been confirmed outside this study by other workers. Collectively, the genotypic and phenotypic data reported suggest that the BD-2 group represents a subspecies of A. hydrophila, for which the name Aeromonas hydrophila subsp. dhakensis subsp. nov. is proposed. Its type strain is P21T (= LMG 19562T= CCUG 45377T). An extended description of A. hydrophila subsp. hydrophila (Chester 1901) Stanier 1943 (Approved Lists 1980) is given.