Intestinal infections are a large group of diseases caused by pathogenic or opportunistic bacteria, viruses and protozoa. The leading symptom of such pathologies is diarrhea. Such diseases are very widespread in the world, including developed countries.
All intestinal infections are treated in the same way, therefore, identifying a specific pathogen is important not to the attending physician, but to epidemiologists studying the distribution paths, transmission methods, manifestations of the disease in each new case, treatment effectiveness and other characteristics of the bacterium or the pathogen virus. This information is extremely important, given the widespread spread of intestinal infections on the planet and their high infectivity, as bacteria and viruses change. In addition, the pathogen is established to understand what preventive measures should be taken to prevent infection of other people.
One way to identify an infectious agent is to use a feces bacteriological test. It is carried out at any visit to the doctor with complaints of diarrhea. This is the most universal way to identify the causes of intestinal infection, which does not require sophisticated equipment.
Bacteriological analysis of feces is based on a study of the physiological properties of the pathogen identified in the biomaterial. It includes cultivation, isolation of pure cultures, identification and typing of pathogens.
Classification of intestinal infections
We list the diseases that belong to the group of intestinal infections.
1. Caused by bacteria:
- Cholera.
- Botulism.
- Typhoid fever and paratyphoid (salmonellosis).
- Shigillosis (dysentery).
- Escherichiosis (coli infection).
- Other bacterial infections are campylobacteriosis, yersiniosis.
2. Caused by the simplest:
- Amoebiasis.
- Giardiasis and others
3. Caused by viruses:
- Rotavirus.
- Adenovirus.
- Norovirus and others.
4. Caused by opportunistic microorganisms:
- Staphylococci (there are conditionally pathogenic and pathogenic, for example, Staphylococcus aureus).
- Klebsiella.
- Citrobacter (there are pathogenic and opportunistic strains).
- E. coli.
- Proteus and others
5. Intestinal infections of unknown etiology.
6. Mixed intestinal infections.
In 40% of cases, the causative agent of intestinal infection is viruses, in 20% - bacteria, in 40% the pathogen cannot be established.
According to the WHO, acute intestinal infections account for 30% of deaths in children under 5 years of age.
How to pass the analysis
Preparation for the analysis of feces for bacteriological examination includes special rules:
- Using a special container for collecting feces. The doctor can give a special test tube with a nutrient medium and a sterile rectal loop.
- Preparation of the vessel - treat it with a disinfectant solution, rinse it several times with running water, pour over boiling water.
- Do not touch the spoon, the inner walls of the container and the lid.
- You can not take an analysis after taking antibiotics.
- Carrying a thorough toilet of the anus.
The sample should reach the laboratory as soon as possible. Storage of material for 2 hours at room temperature and 3 hours at a temperature of 2-8 ° C is allowed. To identify some pathogens, sowing on a nutrient medium is necessary immediately after taking the biomaterial.
Stages of bacteriological analysis of feces
1 day. Sowing material on differential diagnostic media.
These are special nutrient media used to identify groups of bacteria that differ in their ability to utilize a particular substance. For example, lactose is often added to the culture medium to grow intestinal pathogens. Some bacteria (E. coli) break it down. Then, colored colonies of microorganisms grow on the surface of the medium. Some microorganisms do not break down lactose (salmonella). Then unpainted colonies grow.
2 day. The grown colonies are examined under a microscope and described. Gram stain and reseed on other specific media for the accumulation of a pure culture of the pathogen.
3 day. With bacteria in pure cultures, agglutination reactions are carried out. Result crops on other media (Gissa) to determine the enzymatic activity.
4 day. The results of the agglutination reaction, growth on Giss media are evaluated. Based on the information received, they give a final answer about the type of pathogen present in the feces.
Deciphering the result
A standard analysis of feces for bacteriological examination includes the identification of several groups of bacteria. Particular attention is paid to E. coli - its colonies with different enzymatic properties are separately reported. Most of these bacteria belong to the group of opportunistic pathogens. That is, they live in the intestines as saprophytes, but under certain conditions they become pathogenic. A standard study includes bacteriological analysis of feces for dysbiosis. What bacteria can be detected in the sample? This can be found in the analysis result below (for an example).
E. coli, or Escherichia coli (E. coli)
These microorganisms colonize the baby’s large intestine immediately after birth. Here they prevail among facultative anaerobic bacteria. E. coli perform many useful functions in the human body. They contribute to the development of immunity to pathogenic varieties of bacteria, and also produce substances that inhibit the growth of other microorganisms.
Bacteria of the species E. coli are pathogenic and conditionally pathogenic. Under the microscope, one and the other look the same. They are distinguished by the structure of antigens located on the surface of bacteria. To do this, conduct a serological study. Conditionally pathogenic E. coli live in the large intestine, but against the background of immunodeficiency can cause inflammation in other organs, for example, in the urinary tract. Pathogenic representatives of E. coli are called diarrheagenic. They belong to transient bacteria, that is, they are not permanently localized in the body. When they enter the intestinal tract, they cause diseases under the general name Escherichiosis, the main manifestation of which is diarrhea.
Deciphering the results of the determination of the amount of E. coli
A standard bacteriological analysis of feces for the intestinal group of infections includes such calculations of the number of Escherichia coli:
- The total number of E. coli.
- The sticks are typical.
- With poorly expressed enzymatic properties.
- Lactose-negative.
- Hemolytic.
The total amount of Escherichia coli in 1 g of feces in children ranges from 400 million to 1 billion, and in adults - 300-400 million. Excessive multiplication of bacteria in the intestine leads to dysbiosis.
Typical (classic) E. coli are good for the body. Their normal amount in feces should be in the range of 10 7 -10 8 . The decrease indicates intoxication, leading to the death of beneficial microflora in the large intestine, as well as the colonization of the intestine with parasites - worms or protozoa. Other causes are high sensitivity to allergens, damage to the liver, kidneys, pancreas and thyroid gland.
The high content of these bacteria in the feces indicates their excessive reproduction, which can lead to the appearance of purulent inflammations of different localization.
Escherichia coli with reduced enzymatic activity - "parasites." With normal immunity, they do not cause disease, but they do not bring benefits either. Such bacteria take the place of beneficial E. coli. As a result, the body loses a number of substances, including vitamins. Normally, they should be no more than 10 5 . Their increase always indicates dysbiosis and can lead to inflammation.
Species of E. coli that do not ferment lactose (lactose-negative) are pathogenic. They infect the cells of the colon, causing diarrhea. The amount of these bacteria in the stool should not exceed 10 5 . If a patient with diarrhea has more of them, for example 10 6 or 10 7 , then these microorganisms were the cause of the disease. Inability to use lactose and some other properties make them similar to shigella - pathogens of dysentery.
Hemolytic Escherichia coli are pathogenic, localized mainly in the cecum. Hemorrhagic colitis with symptoms of general intoxication (nausea, vomiting) is caused. Normal in feces are absent.
Conditionally pathogenic microorganisms that can cause intestinal infection
Increasingly, bacteria that constantly live in the human large intestine cause infections of various localization - the digestive tract, respiratory or genitourinary system. This is caused by a deteriorating environmental situation, the uncontrolled use of antibiotics and other drugs, the constant presence of bacteria in the human environment. Newborns and children of the first 6 months of life, as a rule, fall ill.
You can perform a bacteriological analysis of feces in Invitro. This is a network of laboratories with branches in all major cities. Patients like the fact that the results of the analysis can be obtained online, that is, you do not need to go to the laboratory for them.
Staphylococci
There are three types of bacteria of the genus Staphylococcus that can cause intestinal infection:
- Staphylococcus aureus (Staphylococcus aureus).
- Epidermal.
- Saprophytic.
Staphylococcus aureus is the most pathogenic of them, that is, when ingested, it always causes the development of the disease. Therefore, in the results of the analysis, it is usually prescribed in a separate line. Normally, Staphylococcus aureus should not be in feces. The picture shows a pure culture of Staphylococcus aureus under a microscope.
The epidermal species is also pathogenic, but it is less aggressive than the golden one, that is, it can be present in the body without damaging it. Saprophytic species is a common inhabitant of the large intestine. The total number of epidermal and saprophytic staphylococci should not exceed 10 4 .
Intestinal pathogens
Bacteriological analysis of feces for a pathogenic intestinal group includes the determination of bacteria of the genus Salmonella and the genus Shigella. They are pathogenic, that is, if they enter the intestines, they cause pathologies - salmonellosis, typhoid fever, dysentery. Normally absent in the body, so do not stand out with feces.
Less commonly, other pathogenic microorganisms that can cause intestinal infections are found in feces.
Stool viruses
In children of the first year of life, various viruses can be the causative agents of intestinal infections. When stool is analyzed by microscopic and bacteriological methods, viruses are not detected.
The detection of any intestinal infections in the feces requires hospitalization of children under 3 months of age. Hospitalization is also desirable for children up to a year.
When establishing dysentery, salmonellosis, staphylococcal infection, foodborne toxic infections, escherichiosis in adults and children older than a year, home treatment is prescribed. If the course of the disease is severe or there is a high degree of risk of the spread of the disease, patients are hospitalized in an infectious diseases hospital.