SHIGELLAS

From Big Medical Encyclopedia

SHIGELLAS — the bacteria making the family Shigella of the Entero-bacteriaceae family. Highways pathogens for the person (see Dysentery) and monkeys, generally humanoid, however are described dizenteriyepodobny diseases and shigellezny sepsis at young growth of nek-ry animals.

Sh. received the generic name by name K. Shigi who in detail studied in 1898 during epidemic of dysentery in Japan of an infestant nowadays known as Shigella dysenteriae 1. On the International classification

of shigellas (1958) the sort Shigella includes 4 subgroups and respectively types: And. —

S. dysenteriae, V. — S. flexneri, With — S. boydii and D-S. sonnei differing on biochemical properties and composition of antigens. Taking into account the additions made to classification of shigellas by the International subcommittee by enterobakteriya in 1982 in a type of S. dysenteriae distinguish 12 serotypes (serovars), the type of S. flexneri is made by subserotypes (under - serovars) la, lb, 2a, 2, For, Z, 4a, 4, 5a, 5, a serotype 6 (S. new-castle), X-variant, Y-variant, an at

S. boydii distinguish 18 serotypes. In the USSR and nek-ry other countries allocation of S. flexneri 4 with an antigenic formula IV is registered: 7, 8, there is no edge in the operating classification of shigellas.

Shigellas — sticks with the rounded-off ends 2 — 3 microns long, 0,5 — 0,7 microns wide. Capsules, and flagellums they have no dispute. The majority of iodserotip of S. flexneri is supplied with fimbrias, or pilyam. Distinguish the general and sexual saw — hollow shoots on a surface of a bacterial

cell 0,3 — 2 microns long and 0,01 microns wide. Consider that the general drank, increasing a surface of a cell of a bacterium, create it the best conditions for digestion of nutritious substrates and oxygen. Their participation in adhesion (sticking) of bacteria, in particular to an epithelium of a mucous membrane of a large intestine is proved. The general drank are controlled by chromosomal genes, synthesis of sexual pileas is regulated by extra chromosomal elements — plasmids (see). Sexual saw serve as pairing channels by transfer of genetic material (see Conjugation at bacteria). Being heterogeneous on the structure and specific structure of antigens, they are capable to adsorb donorspetsifichesky RNA - and DNA-containing a phage that is the basis for criteria of their classification. F-like and I-like sexual pilyam there correspond F-and I-fagi adsorbed by these pilyam.

Except S. dysenteriae 1, exotoxin can form S. dysenteriae 3 — 7, S. sonnei, S. flexneri

6, however in smaller quantity (in 1000 and more time), than S. dysenteriae

1. Shigellas are not mobile, do not split adonit, an inositol, salicin, cellobiose, do not hydrolyze urea, do not liquefy to gelatin. Glucose and nek-ry other carbohydrates are split with education only to - you (except for nek-ry gas-forming strains). Nek-ry representatives of Sh. can produce a r-galactosidase, to an ornitinde-carboxymanhole and argininedihydrolase. To Fenilalanindezaminaz, whether-zindekarboksilazu Sh. do not produce. Highways cannot use citrate, acetate, malonate, D-tartrate. Growth of bacteria is suppressed with potassium cyanide. An indole by training Sh. are variable, and they do not form hydrogen sulfide and methyl-acetyl carbinol.

Shigellas have O-antigens, and nek-ry of them and K-antigens. O-antigens are a component of a cell wall of bacteria. They represent lipopolisakharidoproteinovy complexes, from to-rykh a polisakharidny component causes serological specificity. The last depends on a chemical structure of O-specific polisakharidny side chains of a lipopoli-sakharid. Availability of K-antigens is assumed at S. dysenteriae,

S. flexneri 6, S. boydii. K-antigens

are the acid polysaccharides located in more superficial part of a bacterial cell than O-antigens, and unlike them a termolabilna.

Highways are unstable to influence physical. - chemical and biol. factors. They perish instantly at boiling, within 10 min. in UV rays and 30 min. at a direct sunlight. In a gastric juice only several minutes survive, in fecal samples can remain not longer than 6 — 10 hours, gradually perishing under the influence of a bacteriophage, acid reaction of the environment and microbic antagonism. However in the dried-up or frozen excrements (— 20 °) shigellas remain viable within several months. Sh.'s preservation in water, the soil and foodstuff partially depends on their specific accessory (are steadiest S. sonnei, least — S. dysenteriae) and substantially — on heating environments and an obsemenennost other microorganisms.

Bibliography: Short determinant of bacteria of Bergi, under the editorship of J. Hoult, the lane with English, M., 1980; About Committee of the USSR on taxonomy and nomenclature of pathogenic bacteriums, protozoa and mushrooms, Zhurn. mikr., epid. and immun., No. 4, page 119, 1980; P r I-mukhina am N. S., Kolobova of JI. T. and Bobrova T. P. Preservation and indication of shigellas in the environment, M., 1983, bibliogr.; Pryamukhina N. S., etc. Modern ideas of biology of activators and methods of laboratory diagnosis of bacterial dysentery, M., 1981; S e 1 t m a n n G. Immunochemistry of shigellas, Zhurn. mikr., epid. and immun., No. 7, page 20, 1977; Tim -

k V. D., Petrovsky V. G. and Bondarenko V. M. Biological and genetic characteristics of bacteria of the sort Shigella, M., 1980; Brenner D. J. Recommendations on recent proposals for the classification of Shigellae, Int. J. system. Bact., v. 34, p. 87, 1984; Edwards P. R. a. Ewing W. H. Identification of enterobacteriaceae, Minneapolis, 1972; Ewing W. H. Biochemical reactions of Shigella, Atlanta, 1971; Shiga K. t } ber den Dysenteriebacillus (Bacillus dysenteriae), Zbl. Bakt., I. Abt., Bd 24, S. 817, 870, 913, 1898.

H. S. Pryamukhina.

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