Genus Edwardsiella
Taxonomy
Morphology
Cultural characteristics
Biochemical characters
Ecology
Pathogenicity
References
Phylum Proteobacteria, Class Gammaproteobacteria, Order Enterobacteriales, Family Enterobacteriaceae, Genus Edwardsiella,
- Edwardsiella ictaluri Hawke et al. 1981,
- Edwardsiella hoshinae Grimont et al. 1981,
- E
dwardsiella piscicida Abayneh et al. 2013,
- Edwardsiella tarda (E. anguillimortifera) Ewing & McWhorter 1965 - type species of the genus.
Grimont et al. (1980) described a new biogroup designated
E. tarda biogroup 1, only biochemically differentiated from E. tarda (see
table).
Gram negative, straight bacilli, 1.0 x 2.0–3.0 μm, usually motile by peritrichous flagella
(nonmotile strains may occur). No capsule production.
Growth occurs on usual media, producing small colonies (0.5–1.0 mm in diameter)
after 24 h incubation. Optimum temperature, 37 ºC.
E. ictaluri appears as smooth, circular (1-2 mm diameter), slightly convex non-
pigmented colonies. Center-black colonies on SS agar. Facultatively anaerobic.
Incubation temperature 28-37 ºC. The bacteria grows slowly but does not require
special nutrients.
E. piscicida on blood agar after 24 h of incubation at 30 ºC is pin-point, circular,
slightly convex, smooth and glistening with slight beta-haemolysis visible only under
the colony. Growth can occur at 25, 37 and 42 ºC but not at 12 ºC. Growth occurs at
NaCl concentrations of 1–3% but not at 5% or above.
Isolated from water, aquatic animals and reptiles and found in the intestinal tract of snakes and seals. They are occasionally isolated
from the urine, blood, and feces of humans (diarrhoea). Usually resistant to colistin but susceptible to most other antibiotics,
including penicillin.
They are occasional opportunistic pathogen for humans.
E. hoshinae - no evidence that can cause human disease.
Edwardsiella ictaluri - pathogen for catfish (Ictalurus punctatus), E. ictaluri causes
'enteric septicaemia of catfish' (disease may have 2 forms: chronic encephalitis or
acute septicaemia’, may cause sudden massive die-offs of up to 50% of pond
population.). One report of hepatic abscesses in dog.
Edwardsiella tarda - may cause gastroenteritis and wound infections in humans.
Produces the disease commonly known as fish gangrene, emphysematous
putrefactive disease of catfish or red disease of eels. Produce hemorrhagic ulcers on
the body and fins. Bacteria has a broad host range and causes diseases in
freshwater & marine fish, reptiles, birds and mammals.
E. tarda virulence factors:
adhesion and invasion of epithelial cells, anti-phagocyte-mediated killing, production
of haemolysin and other toxins.
Edwardsiella piscicida is pathogenic for zebra fish.
  1. Don J. Brenner and J.J. Farmer III, 2001. Family I. Enterobacteriaceae. In:  Bergey’s Manual of Systematic Bacteriology, Second
    edition,Vol two, part B, George M. Garrity (Editor-in-Chief), pp 587-897.
  2. J. G.Holt et al., 1994. Begey’s manual of Determinative Bacteriology, 9th-edition, Williams & Wilkins.
  3. Farmer et al.: Proposal to conserve the specific epithet tarda over the specific epithet anguillimortiferum in the name of the
    organism presently know as Edwardsiella tarda: Request for an Opinion. Int. J. Syst. Bacteriol., 1976, 26, 293-294.
  4. De Vos et al.: Judicial Commission of the International Committee on Systematics of Prokaryotes Xth International (IUMS)
    Congress of Bacteriology and Applied Microbiology. Minutes of the meetings, 28, 29 and 31 July and 1 August 2002, Paris, France.
    Int. J. Syst. Evol. Microbiol., 2005, 55, 525-532.
  5. T. Abayneh, D.J. Colquhoun, H. Sorum. Edwardsiella piscicida sp. nov., a novel species pathogenic to fish. J. Appl. Microbiol., 114,
    644-654..
Positive results for catalase, lysine decarboxylase, nitrate reduction, ornithine decarboxylase, acid production from: maltose,
mannose & glucose (usually with gas production).

Negative results for oxidase, Voges–Proskauer, citrate utilization (Simmons), arginine dihydrolase, phenylalanine deaminase,
gelatinase, urease (Christensen), beta-galactosidase, beta-glucuronidase, L-pyrrolidonyl aminopeptidase, lipase (Tween 80), DN-
ase, esculin hydrolysis, growth in KCN medium, acid production from: adonitol, D-arabitol, alpha-methyl-D-glucoside, D-cellobiose,
dulcitol, inositol, lactose, melibiose, raffinose, L-rhamnose, D-sorbitol & D-xylose.

E. piscicida can only be differentiated from E. tarda by degradation of alpha-methyl-D-glucoside, citric acid and L-proline.
(c) Costin Stoica
Antibiogram
Encyclopedia
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R E G N U M
PROKARYOTAE
Legend:  + positive 90-100%, - negative 90-100%, [+] positive 75-89%, [-] negative 75-89%, d positive 25-74% of strains
 
Hydrogen
sulfide (TSI)
Methyl red
Indole
production
L-Arabinose
fermentation
D-Mannitol
fermentation
Sucrose
fermentation
Trehalose
fermentation
E. tarda / E. piscicida
+
+
+
-
-
-
-
E. tarda biogroup 1
-
+
+
+
+
+
-
E. hoshinae
+
+
d
[-]
+
+
+
E. ictaluri
+
-
-
-
-
-
-
Differential characters between species:
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