Shigella

Shigella is a genus of intestinal bacteria, including different types of pathogens of dysentery. Domestic classification (1962) divides this kind of biochemical signs into three groups: 1) nesparova mannitol (species Grigorieva - Shigi, Fitting - Shmitta, Large - Sachs, pharmaceutical), 2) sbyivayutsya mannitol - view of the Flexner, including 3 subspecies (actually the Flexner, Newcastle, Boyd), and 3) slowly disintegrating lactose (view sonnei). Further differentiation Shigella on types and subtypes is on serological characteristics that are based on features of the antigenic structure.
The pathogens of dysentery - gram still sticks length of 2-3 MK, of a width of 0.6 MK, easily multiply on a regular nutrient mediums at the temperature of 37 degrees. By type of breathing - aerobes and facultative anaerobes, on the surface of the agar form a semi-transparent tender colony.

Shigella is a genus of pathogenic for humans and monkeys microorganisms; belongs to the family of intestinal bacteria (Enterobacteriaceae).
The first representative of the kind described by Shigai (K. Shiga); his name and the family.
There are two classification schemes Shigella: adopted in the USSR (1962) and international (1950-1958). These schemes comparable, because they include single list Shigella; based on a single principle of the division of dysentery bacteria in their attitude to mannitol and antigenic structure. All Shigella, except for the subspecies of the Flexner, antigenically distinct from each other and have "their" species - or typespecific antigen. Shigella species Flexner contain along with typespecific antigen determining serological type, number of group antigens (see Dysentery, etiology). The latter allows to differentiate the sticks Flexner, with single typespecific antigen (single serotype), serological subtypes (table. 1).

Table 1. Feature group antigens Shigella the Flexner different serological types and subtypes (International classification scheme)
Serological type Subtype Antigens
typespecific group
1 1a I 3,4
1b 3,4 6
2 2a II 3,4
2b 7,8
3 3a III 6 7,8
3b 3,4 6 (7,8)
3c 6
4 4a IV 3,4
4b (3,4) 6
5   V 7,8
  x - 7,8
y - 3,4

The definition of subtype is carried out by a special group set agglutinating sera in experiments agglutination on the glass. Shigella subspecies of the Flexner, unlike the rest of the family representatives, have the so-called fibreline, or ciliate, antigens that are common to all serological types.
The virulence of Shigella (pathogenicity to humans) determine currently on the number of laboratory models - sample Serena eye Guinea pig, "lung" model of M. K. Voino-Yasenetsky, growing in tissue culture (B. A. Arbuzov). Shigella differentiate on morphology, biochemical properties and agglutinating characteristic. In table. 2 provides a list occurring in Shigella enzyme variants.

Table 2. Deviations of some characteristics of dysentery bacteria
Signs Regularity Deviation
Mobility Stationary Unknown
Flatulence Not forming gas Only Newcastle
Fermentation Mannitol Not fermented: Grigoriev - Shiga, Fitting - Schmitz, the large - Sachs Only the large - Sachs (single observation)
Fermented: Flexner, Newcastle, Boyd, Sonne Newcastle (original strain occurs extremely rarely). Flexner, Sonne, Boyd (very rare)
Lactose Fermented: only sonnei Sonnei (extremely rare), Boyd 9, separate versions of this serotype slowly break down lactose
Xylose Not fermented: Flexner, Newcastle Serotype 4 (Boyd 103), some rare species
Dulcet Not fermented: Flexner, Sonne Unknown
Sorbitol Not fermented: sonnei Unknown

Serological identification, especially when using the method agglutination on glass with minoritarnymi sera, it is necessary to consider the availability of serological links between Shigella and the representatives of some of serological groups Escherichia. Somatic antigens of a number of Shigella and Escherichia identical.
Shigella, like several other representatives of the family of intestinal bacteria have the ability to produce colicins and the nature of the produced kolicina can be subdivided into a number of different Kaliningradian. Cm. also Bacteria.