Ornithine
decarboxylase
Citrate
utilization
Malonate
utilization
Indole
production
Melibiose
fermentation
Dulcitol
fermentation
D-adonitol
fermentation
C. amalonaticus
+
+
-
+
-
-
-
C. freundii
-
[+]
[-]
[-]
+
[-]
-
C. braakii
+
[+]
-
[-]
[+]
d
-
C. farmeri
+
-
-
+
+
-
-
C. gillenii
-
[-]
+
-
d
-
-
C. koseri
(C. diversus)
+
+
+
+
-
d
+
C. murliniae
-
+
-
+
d
+
-
C. rodentium
+
-
+
-
-
-
-
C. sedlakii
+
[+]
+
[+]
d
+
-
C. werkmanii
-
+
+
-
-
-
-
C. youngae
-
[+]
-
[-]
-
[+]
-
Genus Citrobacter
Taxonomy
Morphology
Cultural characteristics
Biochemical characters
Ecology
Pathogenicity
References
Phylum Proteobacteria, Class Gammaproteobacteria, Order Enterobacteriales, Family Enterobacteriaceae, Genus Citrobacter,
C. amalonaticus (Levinea amalonatica)  Young et al. 1971,
C. braakii  (previously known as Citrobacter genomospecies 6) Brenner et al. 1993
C. diversus (C. diversum, Aerobacter diversum, Levinea malonatica ) (actual C. koseri), Braak 1928,
C. farmeri (Citrobacter amalonaticus biovar 1, Citrobacter genomospecies 4),
C. freundii  (Bacterium freundii, Escherichia freundii), Burkey 1928 - type species,
C. gillenii (Citrobacter genomospecies 10),
C. murliniae (Citrobacter genomospecies 11),
C. rodentium (C. freundii biovar 4280, Citrobacter genomospecies 9),
C. sedlakii (Citrobacter genomospecies 8),
C. werkmanii (Citrobacter genomospecies 7),
C. youngae (Citrobacter genomospecies 5).
Gram negative, straight rods, 1.0 x 2.0–6.0 μm, found singly or in pairs. Frequently
motile by means of peritrichous flagella. Usually not encapsulated.
Colonies on nutrient agar are generally 2–4 mm in diameter, smooth, low convex,
moist, translucent or opaque, and gray with a shiny surface and entire edge. Mucoid
or rough forms may occur.
Facultatively anaerobic. Incubation temperature 37
°C.
Media: Trypticase Soy Agar with 5% sheep blood, Nutritive Agar. Grows on media that inhibit
Escherichia coli: Muller’s tetrathionate
broth, Leifson’s selenite broth, Wilson-Blair  bismuth sulfite, Kristensen briliant green-phenol red agar.
Isolated from soil, water, seawage, food, feces, urine, clinical samples (humans and
other animals including mammals, birds, reptiles and amphibians).
They seem to be normal intestinal inhabitants but may occur in sporadic and mass
alimentary infections or some urinary tract infections, respiratory tract infections,
wound infections, osteomyelitis, meningitis & brain abscesses (young organisms are
more sensitive), enteritis, septicemia.

C. amalonaticus found responsible of enteric fever-like illness (one report).
Citrobacter freundii is often found in clinical specimens as an opportunistic or
secondary pathogen.
Citrobacter rodentium is the causative agent of Transmissible Murine Colonic
Hyperplasia.
O, K and H antigens presented. Cross-reactions identified with antisera of the other
members of the Enterobacteriaceae (Salmonella, Escherichia).
  1. J. G.Holt et al., 1994. Begey’s manual of Determinative Bacteriology, 9th-edition, Williams & Wilkins.
  2. 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.
  3. Werkman (C.H.) and Gillen (G.F.): Bacteria producing trimethylene glycol. Journal of Bacteriology,1932, 23,167-182
  4. Ewing(W.H.) and Davis (B.R.): Biochemical characterization of Citrobacter diversus (Burkey) Werkman and Gillen and designation
    of the neotype strain. Int. J. Syst. Bacteriol., 1972, 22, 12-18.
  5. Validation list 8. Int. J. Syst. Bacteriol., 1982, 32, 266-268. [FARMER III (J.J.): The genus Citrobacter.
  6. M.P. STARR et al. (ed.), The procaryotes, a handbook on habitats, isolation, and identification of bacteria.Springer-Verlag, Berlin,
    1981, p. 1140-1147
  7. Abbot SL, Klebsiella, Enterobacter, Citrobacter, Serratia, Plesiomonas, and other Enterobacteriaceae. In: Murray PR, Baron EJ,
    Jorgensen JH, Pfaller MA, Yolken RH. Manual of clinical microbiology. 8th edition. Washington DC: American Society for
    Microbiology, 2003:684-700
  8. DON J. BRENNER, Biochemical Identification of citrobacter Species Defined by DNA Hybridization and Description of Citrobacter
    gillenii sp. nov. (formerly C. genomospecies 10) and C. murliniae sp. nov. (formerly Citrobacter genomospecies 11), Journal of
    Clinical Microbiology Aug. 1999, p. 2619–2624, Vol. 37, No. 8.
Positive results for catalase, methyl red, ONPG (most of strains), nitrate reduction, mucate (most od strains), Tartrate (Jordans), acid
production from: glucose (with gas), L-arabinose, maltose, L-rhamnose, trehalose, D-xylose, D-mannitol, mannose & D-sorbitol.

Negative results fo oxidase, lysine decarboxylase, Voges-Proskauer, phenilalanine, gelatinase, esculin hydrolysis (most of strains),
deoxyribonuclease, lipase, acid production from: erythritol & myo-inositol.
(c) Costin Stoica
Antibiogram
Encyclopedia
Culture media
Biochemical tests
Stainings
Images
Movies
Articles
Identification
Software
R E G N U M
PROKARYOTAE
Differential characters between species:
Legend: +  positive 90-100%, - negative 90-100%, [+] positive 75-89%, [-] negative 75-89%, d positive 25-74% of strains
Previous page
Back