180
T. BERGAN
elaborated in Denmark by BojlCn (1934) who extended Thjntta’s classification with a type IV, which corresponds to Schmitz’s bacillus and is now
S. dysenterioe type 2.
In 1949, Ewing proposed the present taxonomic scheme for the genus
Shigella dividing it into, S. dysenteriae, S. Jexneri, S. boydii, and S. sonnei.
Six serotypes, characterised by Boyd between 1928 and 1938, became S.
boydii serotypes 1-6 (Ewing et al., 1971).
Soviet bacteriologists have used another classification scheme according
to which (a) S. grigorev-shiga and S. stuxeri-schmitxii correspond to S.
dysenteriae, (b) S. Jexneri and S. newcastle equal the international S.
Jexneri, and (c) S. boyd-novgorod correspond to S. boydii.
Shigella isolates are Gram-negative, catalase-negative, non-motile, nonencapsulated, aerobic, facultatively anaerobic rods. They cannot use
citrate or malonate as sole source of carbon or produce HzS, gas from
glucose (except aerogenic strains of S. Jexneri type 0:6), acid from mucinate, arginine hydrolase (except S. sonnei, a few strains), or lysine decarboxylase, but S. sonnei as a rule has ornithine decarboxylase. No growth
occurs in the presence of KCN (Carpenter, 1974).
Although shigellae usually do not produce acid from lactose, some S.
sonnei possess b-galactosidase (exhibit a positive ortho-nitrophenylP-D-galactoside test, ONPG). A few strains are even clearly lactose
positive to the same extent as the most common Escherichia coli. A few
S. sonnei strains are indole positive. Differentiating biochemical-cultural
characteristics appear in Table I.
111. SEROLOGY OF SHIGELLA
A. Major serogroups of Shigella
The antigenic composition of shigellae is important for variation in
susceptibility to phages, since their receptor sites are surface structures.
Serology also forms the basis of Shigella classification.
Shigella has O-antigens and envelope antigens of the K-variety. Group
and type specific O-antigens are present on the colony S-form of cells.
The more infrequent K-antigens inhibit agglutinability in O-sera. Kantigens are removed by boiling in water for 1 h. R-form colonies have core
R-antigens which are common for all shigellae.
Electron microscopic studies (Vaneeva et al., 1976) have shown that Sform cells have a relatively smooth surface. They differentiated between
phase I1 cells and R-cells. The former had a smooth surface with cell wall
fragments split off from it, whereas the latter had a coarse, folded surface
with numerous fragments split off most cells.
T. BERGAN
elaborated in Denmark by BojlCn (1934) who extended Thjntta’s classification with a type IV, which corresponds to Schmitz’s bacillus and is now
S. dysenterioe type 2.
In 1949, Ewing proposed the present taxonomic scheme for the genus
Shigella dividing it into, S. dysenteriae, S. Jexneri, S. boydii, and S. sonnei.
Six serotypes, characterised by Boyd between 1928 and 1938, became S.
boydii serotypes 1-6 (Ewing et al., 1971).
Soviet bacteriologists have used another classification scheme according
to which (a) S. grigorev-shiga and S. stuxeri-schmitxii correspond to S.
dysenteriae, (b) S. Jexneri and S. newcastle equal the international S.
Jexneri, and (c) S. boyd-novgorod correspond to S. boydii.
Shigella isolates are Gram-negative, catalase-negative, non-motile, nonencapsulated, aerobic, facultatively anaerobic rods. They cannot use
citrate or malonate as sole source of carbon or produce HzS, gas from
glucose (except aerogenic strains of S. Jexneri type 0:6), acid from mucinate, arginine hydrolase (except S. sonnei, a few strains), or lysine decarboxylase, but S. sonnei as a rule has ornithine decarboxylase. No growth
occurs in the presence of KCN (Carpenter, 1974).
Although shigellae usually do not produce acid from lactose, some S.
sonnei possess b-galactosidase (exhibit a positive ortho-nitrophenylP-D-galactoside test, ONPG). A few strains are even clearly lactose
positive to the same extent as the most common Escherichia coli. A few
S. sonnei strains are indole positive. Differentiating biochemical-cultural
characteristics appear in Table I.
111. SEROLOGY OF SHIGELLA
A. Major serogroups of Shigella
The antigenic composition of shigellae is important for variation in
susceptibility to phages, since their receptor sites are surface structures.
Serology also forms the basis of Shigella classification.
Shigella has O-antigens and envelope antigens of the K-variety. Group
and type specific O-antigens are present on the colony S-form of cells.
The more infrequent K-antigens inhibit agglutinability in O-sera. Kantigens are removed by boiling in water for 1 h. R-form colonies have core
R-antigens which are common for all shigellae.
Electron microscopic studies (Vaneeva et al., 1976) have shown that Sform cells have a relatively smooth surface. They differentiated between
phase I1 cells and R-cells. The former had a smooth surface with cell wall
fragments split off from it, whereas the latter had a coarse, folded surface
with numerous fragments split off most cells.