Genus Shigella
Taxonomy
Morphology
Cultural characteristics
Biochemical characters
Ecology
Pathogenicity
References
Phylum Proteobacteria, Class Gammaproteobacteria, Order Enterobacteriales, Family Enterobacteriaceae, Genus Shigella,
Shigella boydii  Ewing 1949,
Shigella dysenteriae  Castellani and Chalmers 1919 - type species of the genus, old synonym: Bacillus dysentericus Shiga 1897,
Shigella flexneri Castellani and Chalmers 1919,
Shigella sonnei (Levine 1920) Weldin 1927.

The Shigella species and Escherichia coli are a single species on the basis of DNA relatedness,
but they remain separate species to avoid confusion.
Gram negative rods, non-motile, non-encapsulated.
S-type colonies, nonpigmented. Facultatively anaerobic, growth temperature 37 ºC.
Media: Nutrient Agar or Nutrient Broth, Trypticase Soy Agar ± 5% sheep blood, Mac
Conkey Agar.
Widely distributed in nature. Isolated from feces, water & soil. The normal habitat is intestinal tract of man & apes.
Shigella species are commonly pathogenic to humans, causing severe gastroenteritis (bacillary dysentery), more severe in children.
S. dysenteriae serotype 1 causes more severe disease than other serotypes and produces an exotoxin (Shiga toxin).
  1. J. G.Holt et al., 1994. Begey’s manual of Determinative Bacteriology, 9th-edition, Williams & Wilkins.
  2. Ewing W.H.: Shigella nomenclature. Journal of Bacteriology, 1949, 57, 633-638.
  3. Castellani A. & Chalmers A.J.: Manual of Tropical Medicine, 3rd ed., Williams Wood and Co., New York, 1919, p. 935.
  4. 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.
Positive results for nitrate reduction, methyl red  & acid production from D-mannose.

Negative results for H
2S production, oxidase, lysine decarboxylase, citrate utilization, Voges-Proskauer test, urea hydrolysis,
phenylalanine deaminase, gelatin hydrolysis, esculin hydrolysis, DN-ase, lipase, acetate utilization, acid production from lactose,
salicin, adonitol, myo-inositol, sucrose, alpha-methyl-D-glucoside & mucate.

The four species are often reffered to as subgroups A to D.  Subgroup A strains are mannitol non-fermenters (most of them) and the
other 3 subgroups are mannitol fermenters.
subgroup A: S. dysenteriae (15 serotypes)
subgroup B: S. flexneri (14 serotypes)
subgroup C: S. boydii (19 serotypes)
subgroup D: S. sonnei
S. dysenteriae: catalase is not produced by serotype 1, but is usually produced by strains of other serotypes. Dulcitol is fermented by
strains of serotype 5. Indole production is variable among serotypes.
S. flexneri: dulcitol is fermented by certain biotypes of serotype 6 and 4a some biotypes may produce gas from sugars.
S. boydii: dulcitol is usually fermented by serotypes 2, 3, 4, 6, and 10. Serotypes 13 and 14 may produce gas from sugars.
(c) Costin Stoica
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R E G N U M
PROKARYOTAE
 
ONPG
Ornithine
decarboxylase
Malonate
utilization
Growth on
KCN medium
Glucose
fermentation
L-rhamnose
fermentation
Maltose
fermentation
L-arabinose
fermentation
S. dysenteriae
d
-
+
-
-
d
[-]
d
S. boydii
-
-
-
-
+
-
[-]
+
S. flexneri
-
-
-
+
+
-
d
d
S. sonnei
+
+
-
-
+
[+]
+
+
Legend:  + positive 90-100%, - negative 90-100%, [+] positive 75-89%, [-] negative 75-89%, d positive 25-74% of strains
Differential characters of the species:
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