Genus Yokenella (Koserella)
Cultural characteristics
Biochemical characters
Phylum Proteobacteria, Class Gammaproteobacteria, Order Enterobacterales, Family Enterobacteriaceae, Genus Yokenella,   
Yokenella regensburgei Kosako et al. 1985, synonym: Koserella trabulsii Hickman-Brenner et al. 1985.

Other synonyms: Hafnia hybridization group 3, CDC Enteric Group 45.
Gram-negative, rods. Motile at 36 ºC by peritrichous flagella.
S-type colonies, nonpigmented. Facultatively anaerobic, growth temperature 28-37 ºC.
No growth at 4 ºC.
Media: Nutrient Agar or Nutrient Broth, Trypticase Soy Agar ± 5% sheep blood.
Isolated from water, human clinical specimens (stools, knee fluid, wounds), animals (sheep intestine) and insects.
Resistant to colistin, penicillin, ampicillin, carbenicillin, cephalothin and some strains to streptomycin.
May be associated with bacteremia and wound infections in humans.
  1. J. G. Holt et al., 1994. Facultatively Anaerobic Gram-Negative Rods. Subgroup 1. Family Enterobacteriaceae. In: Begey’s Manual of
    Determinative Bacteriology, 9th-edition, Williams & Wilkins, pp 175-189.
  2. Kosako Y., Sakazaki R. & Yoshizaki E.: Yokenella regensburgei gen. nov., sp. nov.: a new genus and species in the family
    Enterobacteriaceae. Jpn. J. Med. Sci. Biol., 1984, 37, 117-124 (VALIDATION LIST N° 17. Int. J. Syst. Bacteriol., 1985, 35, 223-225).
  3. Kosako Y., Sakazaki R., Huntley-Carter G.P. & Farmer III J.J.: Yokenella regensburgei and Koserella trabulsii are subjective
    synonyms. Int. J. Syst. Bacteriol., 1987, 37, 127-129.
  4. Hickman-Brenner F.W., Huntley-Carter G.P., Richard G.: Koserella trabulsii, a new genus and species of Enterobacteriaceae
    formerly known as Enteric Group 45. Journal of Clinical Bacteriology, Jan. 1985, p. 39-42.
  5. 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.
  6. Adeolu M, Alnajar S, Naushad S, S Gupta R. Genome-based phylogeny and taxonomy of the 'Enterobacteriales': proposal for
    Enterobacterales ord. nov. divided into the families Enterobacteriaceae, Erwiniaceae fam. nov., Pectobacteriaceae fam. nov.,
    Yersiniaceae fam. nov., Hafniaceae fam. nov., Morganellaceae fam. nov., and Budviciaceae fam. nov. Int J Syst Evol Microbiol
    2016; 66:5575-5599.
Yokenella regensburgei can be differentiated from Hafnia species by its ability to utilize citrate and to produce acid from cellobiose,
melibiose and D-arabitol.

Positive results for methyl red, citrate utilization (Simmons), lysine decarboxylase,
ornithine decarboxylase, growth in the presence of cyanide, beta-galactosidase,
tetrathionate reductase, acid production from glucose (with gas production), D-mannitol, L-arabinose, L-rhamnose, maltose,
D-xylose, trehalose, cellobiose, melibiose, D-mannose, D-galactose, L-fucose and D-gluconate.

Negative results for indole production, Voges-Proskauer, H
2S production (TSI), urea hydrolysis, phenylalanine deaminase, arginine
dihydrolase, malonate utilization, gelatin hydrolysis, lipase (corn oil and Tween 80), DN-ase, esculin hydrolysis, pectinase, chitinase,
beta-xylosidase, acid production from adonitol, lactose, sucrose, dulcitol, salicin,  myo-inositol, D-sorbitol, raffinose,
alpha-methyl-D-glucoside, erythritol, D-arabitol, glycerol and mucate.
(c) Costin Stoica
Culture media
Biochemical tests
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