Edwardsiella

Ed.ward.si.el' la . M.L. dim. ending ‐ ella; M.L. fem. n. Edwardsiella named after the American bacteriologist RR . Edwards (1901–1966). Proteobacteria / Gammaproteobacteria / Enterobacteriales / Enterobacteriaceae / Edwardsiella Straight rods , ~1.0 × 2.0–3.0 µm, conforming to the general definition of the family Enterobacteriaceae . Gram negative. Motile by peritrichous flagella , but nonmotile strains may occur. Facultatively anaerobic. Growth occurs on ordinary media with small colonies (0.5–1.0 mm in diameter) after 24 h incubation. Optimum temperature, 37°C, except for E . ictaluri , which prefers a lower temperature. Nicotinamide and amino acids are required for growth . Reduce nitrate to nitrite. Ferment D ‐glucose with the production of acid and often gas. Also ferment a few other carbohydrates but are inactive compared to many taxa in the family Enterobacteriaceae . Usually resistant to colistin but susceptible to most other antibiotics, including penicillin . Frequently isolated from river fish and cold‐blooded animals and their environment, particularly fresh water. Pathogenic for eels, catfish, and other animals, sometimes causing economic losses; also opportunistic pathogen and possibly rare cause of gastroenteritis for humans. A member of the Gammaproteobacteria . The mol % G + C of the DNA is : 53–59. Type species : Edwardsiella tarda Ewing and McWhorter in Ewing, McWhorter, Escobar and Lubin 1965, 37.