The Genus Edwardsiella
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The Genus Edwardsiella SHARON L. ABBOTT AND J. MICHAEL JANDA
Taxonomy In 1965, Ewing and colleagues proposed the creation of a new species, Edwardsiella tarda, to house a collection of 37 strains that were primarily of fecal origin. These strains, extensively studied at the United States Centers for Disease Control and Prevention (CDC) since 1959 and referred to as “bacterium 1483–59,” were sufficiently distinct biochemically from other taxa within the family Enterobacteriaceae to warrant this proposal. Simultaneously, a Japanese group (Sakazaki et al., 1965) had been independently studying a collection of 256 Japanese cultures, mostly from snakes, with similar, though not identical, biochemical properties to bacterium 1483–59 (Farmer and McWhorter, 1984). These reptilian isolates were given the vernacular name “Asakusa Group,” a reference to the place from which they were originally isolated. Others, most notably King and Adler (1964) and Rakovskí and Aldov (1965), described the “Bartholomew Group,” which was a collection of yet other unidentified Enterobacteriaceae strains isolated from diarrheal stools with properties similar to E. tarda. This group of organisms took its name from the county hospital in Columbus, Indiana, where the first fecal isolate had been recovered. Don Brenner at the Walter Reed Army Institute of Research, in a DNA hybridization study (Brenner et al., 1974), tested the validity of E. tarda as a new taxon within the Enterobacteriaceae and its relationship to the other phenotypically similar groups (Asakusa, Bartholomew). Polynucleotide sequence data indicated 1) the relatedness of E. tarda to Escherichia coli K-12 was only 20%, and 2) all 20 strains of E. tarda, isolated from diverse sources and geographic locales, formed a single highly related (88% at 60°C) hybridization group. Furthermore, by DNA-DNA hybridization, members of the bacterium 1483–59, and the groups Asakusa and Bartholomew were found to belong to the same species, E. tarda (Table 1). These studies conclusively established the legitimacy of the genus and species, Edwardsiella tarda, and the relationship
between this taxon and the Asakusa and Bartholomew groups. In 1975, Sakazaki and Tamura challenged the species name “tarda” over the epithet “anguillimortiferum” based upon an earlier published species designation, Paracolobactrum anguillimortiferum, proposed in 1962 by Hoshina, for an organism recovered from eels. This bacterium had biochemical properties identical to those of E. tarda in tests performed in common. However, Hoshina (1962) failed to designate a type strain, and the original culture of P. anguillimortiferum was lost in the intervening years. Because “anguillimortiferum” was validly published first and had taxonomic priority over “tarda,” Sakazaki and Tamura (1975) proposed the name E. anguillimortifera (Hoshina) comb. nov. to replace the illegitimate combination E. tarda. Invoking the first principle of the International Code of Nomenclature of Bacteria, which calls for
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