The causative agent of dysentery: description, characteristics and treatment of the disease

Dysentery can be accompanied by poisoning the body with toxic substances and can cause diarrhea, stomach discomfort and other disorders of the gastrointestinal tract. Since ancient times dysentery is the most common acute disease of the intestine, and called her "bloody diarrhea."


Microbiology bacteria is quite simple. The causative agent of dysentery which causes the disease belongs to the genus Shigella. To date, the causative agent of dysentery consists of 40 types. A common characteristic of Shigella is: small stationary sticks, which are distributed to the gram-negative group. They do not form any capsules or spores. They are not choosy and therefore they can be cultivated on standard culture media. Can not exist in hungry environment malonate or citrate. The microorganisms emit hydrogen sulfide, and do not contain urease. When checking the reaction of Fogasa-Proskauer gives a negative result. They do not form lactose, adonit, Inositol, salicin. These bacteria are able to form catalase, glucose and do not contain phenylalaninemia and disintegrability. Bacteria of the genus Shigella are facultative anaerobes, with the temperature norm for the maturation of 37.2 C. When the temperature increases to higher levels (47S), microorganisms cease to grow. The acid-alkaline environment of pH equal to 6.6 and 7.3. In the cultivation of microorganisms on solid mediums are formed round, convex, almost colorless, with dissociation are growing rough colonies.

We must carefully monitor the heat treatment of food.

The selected microorganisms are formed in the colony, which are of two types:

  • phase 1 – small round convex,
  • phase 2 – large flat.

Classification of intraspecific determine properties of Shigella is formed using two methods:

  • They are divided into 14 b/x type and subtype, as well as on education raminez, xylose, maltose.
  • Unit pageType for susceptibility to a set of phages.

What resistance have Shigella?

These microorganisms have sverkhplastichnost to environmental influences. Infectious agents can survive long enough for cotton fabrics and paper are almost a month in dry Kale up to six months, in the ground up to 5 months, in an aqueous medium from 2 to 9 weeks on fresh vegetables and fruits up to 14 days, and in dairy products – within 2 weeks. If the temperature reaches about 60C, then death occurs in 20 - 25 minutes. These pathogens are susceptible to chlorine and disinfectants.

What pathogenic factors have Shigella?

Important biological functions that are responsible for the pathogenic properties of Shigella is the ability to penetrate the cells of the epithelium, share in them and cause death.

These properties were discovered by scientists in several ways:

  • Keratoconjunctivitis sample (artificial induction in the Guinea pig conjunctivitis, with the introduction of micro-organisms in the eyelid).
  • The cytotoxic sample (contamination by bacteria cells are often used and chicken embryos).
  • Intranasal infection is the induction of pneumonia by artificial means white laboratory mice.

All the pathogenic properties of microorganisms can be divided into several groups:

  • the properties that define the contact with mucous membrane,
  • features that provide resistance to cellular protective mechanisms of the organism and division in cells.
  • the release of toxins and harmful substances that contribute to the formation of pathological features.

The first group includes the processes of adhesion and colonization. Because of their functional role are responsible lipoprotein layer, proteins of the outer membrane sex pili. Also, these factors produce enzymes that are able to liquefy mucus. Such enzymes include hyaluronidase, mucinase, neuraminidase.

The second group includes processes of invasion, contributing to the introduction of microorganisms into the cells, the enterocytes. In these cells and the macrophages they begin to actively divide and are accompanied by cytotoxic and enterotoxicity effect. These functions are closely following genes of plasmid with M. M. 140 MD. These genes are responsible for synthesis of protein structures on the outer membrane. To help these genes also contribute to the chromosomal genes of Shigella: CSR (responsible for keratoconjunctivitis), sut (responsible for cell death) and other genes,which is still not fully found. Feature of Shigella is their high resistance to phagocytosis. This protection occurs due to the presence of the bacteria To the antigen of 3,4-antigen and lipopolysaccharide. In addition, there is a lipid, found In the endotoxin of the bacteria that is responsible for inhibition of the activity of the cellular memory immunity.

Third group. Here the pathogenic factor from Shigella found one 2 endotoxin and exotoxin. The formation of toxins is logged tox-genes converting phages. The enterotoxin activates the enzyme adenylate cyclase and controls the appearance of diarrhea.

The causes of dysentery?

The source of infection is exclusively human. Animals, insects are not able to hurt this disease. Only in laboratory conditions was to shift the source of infection in monkeys. It is possible to become infected with fecal-oral way. The source of the infection can penetrate the water, nutritional, and contact-household way. This is especially true of dairy products.

To protect themselves from dysentery it is necessary to clean running water. It is possible to pass through the filter, you can freeze, you can buy just drinking.

The causes of the disease is the replacement of species composition of microorganisms. It depends on what bacteria are associated with the differentiation of immunity and alteration of the functional characteristics of microorganisms. For example, when S. Dysenteriae returned and began to form the epidemic foci, the scientists suggested that the bacteria increased the number of plasmids, which have increased drug resistance and high virulence.

What symptoms are present with dysentery?

The ripening period of the disease lasts about a week, but occasionally may last for about a day. Usually, the infection begins to be localized in the mucosa in the area of the rectum where the microorganism is implemented. The life cycle proceeds in a loop: first, the micro-organisms with food, air, or the other way it enters the body. Then there is the development of bacteria in the host organism. Next, Shigella penetrate into the cells-enterocytes, and is the division, the violation and rejection of epithelial cells, which leads to the ingress of bacteria into the intestine. The cycle is closed and starts all over again. The speed of the life cycle depends directly on the number of microorganisms that reside in the boundary layer of the intestinal lining. At the end of the growth cycles, the growth of the infection begin forming ulcers that merge to make the intestinal wall is thinner. That is why stool can appear traces of blood and mucus, pus, and nuclear leukocytes. Included with the cytotoxins responsible for cell death, the enterotoxins are responsible for the full intoxication of the host. The clinical picture of the disease can detect only the types of exotoxins made by bacteria, allergic potential and susceptibility of the immune system. But some questions still remained on the surface. One of them is: how is the disease in children up to two years, as the acute phase of the disease passes to the chronic stage, as is the mechanism of local immunity of the intestine, and also acts as a sensitization. The most common symptoms of dysentery are: diarrhea, frequent urinating. If dysentery is in a difficult phase, the circulation can reach up to 30 times, pain in the rectal area, as well as the poisoning of the body toxins and other harmful substances. The severity of diarrhea is determined by the strength of the attack by bacteria of the intestine. The most severe is the disease which is caused by the bacteria S. Dysenteriae and the easy – Shigella sonnei.

How is post-infectious immunity?

Laboratory experiments on monkeys scientists proved that after was dysentery, formed long immunity to this infection. This is due to the anti-microbial antibodies, high productivity of macrophages, antitoxins, T-lymphocytes. Very important role plays also the immune system of the intestinal mucosa. But it has a specific type and a strong immune system forms.

What diagnosis is used in the identification of dysentery?

The main methods include microbiological diagnosis. Microbiology of the pathogen – that is what should be studied first. Usually, as biological material for diagnosis using stool. The workflow looks like: first, a growing bacterial cell. As nutrient media for them to use the environment endo and Ploskireva to obtain individual colonies and culture in its purest form. Next, begin to explore its properties and identification of the pathogen using different agglutinating sera.

What is this serum? Currently producing a special serum, which is determined by the bacterial cell. These include:

Serum used for Shigella, which do not form beckons:

  • to S. dysenteriae 1 and 2,
  • to S. dysenteriae 3-7,
  • to S. dysenteriae 8-12.

Serum used for Shigella, which form beckons:

  • for the model S. flexneri antigens I, II, III, IV, V, VI,
  • to the group antigens of S. flexneri 3, 4, 6,7,8 polyvalent,
  • to antigens of S. boydii 1-18
  • to antigens of S. sonnei phase I, phase II,
  • to antigens of S. flexneri I-VI + S. sonnei polyvalent.

For moreeffective detection of micro-organisms often use a method more like this: a colony, which was at risk of pathogenicity, peresevat on other special medium. It consists of sucrose, glucose, lactose and called transahara agar with the addition of iron. This environment is used in detecting secreted by bacteria to hydrogen sulfide. The second environment, which is also suitable for sowing consists of sucrose, lactose, glucose, urea, and iron.

Every organism that breaks down urea after 4-5 hours of incubation can be attributed to bacteria of the genus Proteus and immediately put to rest, because he will not be pathogenic. If the bacteria in the material begin to give off hydrogen sulfide, or acid edge, also swept aside. But sometimes the exceptions can be checked and the bacteria that produce sulfide, they may belong to the genus Salmonella. The rest of the remaining bacteria should be investigated. You can also review the material on reaction of agglutination on the slide with the necessary serums that help to distinguish Shigella. Also there are other studies that determine the mobility of Shigella.

In order to find antigens in blood and other biological materials can be used methods:

  • the reaction of the passive hemagglutination,
  • reaction of complement binding,
  • the reaction of coagglutination (in the urine and feces),
  • the reaction of IFM,
  • the reaction RAGA (unit-hemaglutinacije),

These studies have high sensitivity and are well suited to diagnose in the early stages.

Also often use different serology. These include:

  • TPPA with the corresponding pure red cell antigens,
  • IFA,
  • the method of Coombs.

It is also reasonable to conduct an allergic test dizenterina. After the procedure, the reaction of the body to check during the day. If the stain is red, becomes pasty, begins to secrete infiltration and increases in size (1.5 to 2 cm), then the reaction is considered positive.

What treatment is used for dysentery?

You first need to resolve your diet and go on a diet. In such diseases as dysentery is very important. Definitely need to normalize the water-salt metabolism and in eliminating toxins and harmful substances from the body.

The main treatment is antibiotics. So as of now the bacteria have become increasingly resistant to antibiotics, then you need to carefully consider their choice. In the early stages is recommended to use a polyvalent dysentery bacteriophage (best if it will be in tablets coated with pectin shell). It is this shell will help

save the bacteriophage released from the hydrochloric acid in the stomach. In the intestine there is a dissolution of the shell, and the phages go out into the lumen, and is already working on the intestinal flora. As the prevention of such tablets it is necessary to give every few days (this is the survival time typical of bacteriophages).

Observe sanitary-hygienic norms. Don't forget to wash hands with soap and water, wet cleaning in the apartment and disinfection.

What preventive measures of dysentery?

In modern times use many methods to make an artificial immunity against the disease. For this purpose, different vaccine from dead microorganisms, alcohol, chemical. However, due to the poor performance of no more use. Was made of a new vaccine:

  • already of live Shigella flexneri,
  • the vaccine is made from ribosomes, which has each cell (ribosome). This vaccine is rarely used.

So to end the problem with the prevention of this disease have not yet decided. Small tips are:

  • improvement of sewer systems,
  • good treatment write,
  • observe the rules of personal hygiene (especially kindergartens and schools),
  • to monitor the quality of food in public places (cafés, eateries).
Buy only fresh vegetables fruits from reliable people. Carefully check the fruit, ensure they were not damaged and overripe. The fruit must be juicy and the skin has to be tight. Do not forget to rinse with boiling water and vegetables.