One of the most dangerous infectious diseases that is gaining momentum recently is diphtheria. It is dangerous not so much by inflammatory processes in the upper respiratory tract, skin, eyes and genitals, but by poisoning the body with toxins of the pathogen - corynebacteria diphtheria. The defeat of the main systems of the body (nervous and cardiovascular) can be quite dangerous, as well as lead to sad consequences. Read about the morphology and microbiology of corynebacteria diphtheria, their pathogenicity and toxicogenicity, ways of infection, symptoms and treatment of the disease in the article
Diphtheria yesterday and today
This disease has been known to mankind since ancient times. He was described in his writings by Hippocrates (460 BC), in the 17th century, diphtheria epidemics mowed down the inhabitants of European cities, and from the 18th century, the inhabitants of North and South America. The name of the disease (from the Greek Diphthera, which means "film") was introduced into medicine by the French pediatrician Arman Trusso. The causative agent of the disease - the bacterium Corynebacterium diphtheriae - was first discovered in 1883 by the German doctor Edwin Klebs. But his compatriot, microbiologist Friedrich Leffler, isolated the bacterium into a pure culture. The latter also belongs to the discovery of the toxin secreted by corynebacteria diphtheria. The first vaccine appeared in 1913, and it was invented by Emil Adolf von Bering, a German microbiologist and doctor, Nobel Prize winner in physiology.
Since 1974, the incidence and mortality from diphtheria has declined significantly in all countries that are members of the World Health Organization, thanks to mass vaccination programs. And if before this, more than a million people were ill every year in the world, and up to 60 thousand died, then after applying vaccination programs, only a few cases of outbreaks of diphtheria are registered. And the greater the percentage of citizens who have undergone preventive vaccinations, the lower the likelihood of epidemics. Thus, a decrease in the coverage of the population of the CIS with vaccinations in the 90s led to an outbreak of the disease, when about 160 thousand patients were registered.
Today, according to health authorities, about 50% of the population is vaccinated against diphtheria, and given that the vaccination schedule requires re-vaccination once every 10 years, more and more often you can hear in the media about a possible epidemiological outbreak of diphtheria in Russia and the countries of the former CIS.
Already not a childhood illness
Diphtheria is an acute, predominantly childhood infectious disease. It is characterized by fibrinous inflammation of the localization site of diphtheria bacillus and severe intoxication of the body with its toxins. But over the past 50 years, this disease has “matured,” and people who are significantly older than 14 years old are increasingly affected by it. In adult patients, diphtheria is a serious illness with a possible fatal outcome.
The most susceptible risk groups are children from 3 to 7 years. Sources of infection can be sick and healthy carriers of the pathogen. The most contagious are patients with diphtheria of the upper respiratory tract, because the main route of infection is airborne. Patients with eye and skin diphtheria can pass the infection through contact. In addition, people who do not have external manifestations of the disease, but are carriers of corynebacteria diphtheria, can become a source of infection - the incubation period of the disease is up to 10 days. Therefore, symptoms do not appear immediately.
Diphtheria is a dangerous disease for an unvaccinated person. In the absence of immediate administration of antidiphtheria serum, the probability of death is 50%. And even with its timely introduction, there remains a 20% probability of a fatal outcome, the causes of which are suffocation, toxic toxic shock, myocarditis and respiratory paralysis.
Genus Corynebacterium
The causative agent of diphtheria Corynebacterium diphtheriae (diphtheria bacillus, or Leffler's bacillus) is part of the genus of gram-positive bacteria, which has more than 20 species. Among bacteria of this genus, there are pathogens of both humans and animals and plants. For practical medicine, in addition to diphtheria bacillus, other representatives of this genus are also important:
- Corynebacterium ulcerans - causes pharyngitis, infectious lesions of the skin, often detected in dairy products.
- Corynebacterium jeikeium - causes pneumonia, endocarditis and peritonitis, infects the skin.
- Corynebacterium cistitidis - may be the initiator of the formation of stones in the urinary tract.
- Corynebacterium minutissimum - provokes an abscess of the lungs, endocarditis.
- Corynebacterium xerosis and Corynebacterium pseudodiphtheriticum - were previously considered causative agents of conjunctivitis and inflammation of the nasopharynx, and today are recognized as saprophytes living on mucous membranes as part of another microflora.
The morphology of corynebacteria diphtheria is similar to the morphology of all representatives of this genus. Diphtheria bacillus has a capsule and constrictions (drank). Corynebacterium diphtheria in the smear are in the form of sticks and are located in relation to each other at an angle, resembling Roman fives. Among the entire variety of representatives of this type of bacteria, there are both toxicogenic forms (producing exotoxins with a pathogenic effect) and bacteria that do not secrete toxins. However, there is evidence that even non-toxicogenic strains of Leffler rods contain genes responsible for the production of toxins in the genome. This means that under appropriate conditions, these genes can turn on.
Virulence and persistence
The causative agent of diphtheria is quite stable in the external environment. Corynebacteria retain their virulence on the surfaces of household items for up to 20 days at room temperature. Microorganisms tolerate drying and low temperatures well. Bacteria die:
- When heat treated at a temperature of 58 ° C for 5-7 minutes, and when boiling - for 1 minute.
- On clothes and bedding - after 15 days.
- In dust, they will die in 3-5 weeks.
- When exposed to disinfectants - chloramine, mercuric chloride, carbolic acid, alcohol - in 8-10 minutes.
The mechanism of the development of the disease
Through the entrance gate (mucous membranes of the tonsils, nose, pharynx, genitals, skin lesions, conjunctiva), corynebacteria diphtheria penetrate the body, where they multiply and produce exotoxin. In the presence of high antitoxic immunity, the toxin is neutralized. But, nevertheless, in the future, two options for the development of the diphtheria pathogen are possible:
- Corynebacteria die and the person remains healthy.
- With insufficient immunity status and high virulence, diphtheria bacilli multiply at the site of invasion and cause healthy bacterial carriage.
If there is no antitoxic immunity , toxigenic corynebacteria diphtheria lead to the development of clinical and morphological signs of infection. The toxin penetrates the tissues, lymphatic and circulatory systems, causes paresis of blood vessels and increased permeability of their walls. Fibrinogenous exudate is formed in the intercellular space, necrotic processes develop. As a result of the conversion of fibrinogen to fibrin, films of fibrous plaque, a characteristic sign of diphtheria, appear on the surface of the affected mucous membranes. With blood, the toxin enters the circulatory system and nervous system, adrenal glands and kidneys, and other organs. There, it leads to disruption of protein metabolism, cell death and their replacement by connective tissue cells.
Pathogen toxins
Corynebacterium diphtheria is characterized by high pathogenicity due to the ability to secrete exotoxin, which includes several fractions:
- Neurotoxin, which leads to necrosis of the cells of the mucous epithelium, dilates blood vessels and increases their permeability. As a result, the liquid component of the blood enters the intercellular space, which leads to edema. In addition, blood fibrinogen reacts with necrotic cells and forms fibrous films.
- The second fraction of the toxin consists of a substance similar in structure to cytochrome C, the protein of all body cells that provides respiration. Corynebacteria toxin replaces the normal cytochrome of the cell and leads to its oxygen starvation and death.
- Hyaluronidase - enhances edema and vascular wall permeability.
- Hemolizing element - leads to the destruction of red blood cells.
These properties of corynebacteria diphtheria, whose task is to spread the pathogenic effect through toxins throughout the body, are the causes of complications of this infection.
Disease classification
Diphtheria is a disease with many forms and manifestations. According to the localization of the invasion, a localized and widespread form of the disease is distinguished.
The shape and version of the flow distinguish:
- Oropharyngeal diphtheria - localized (with catarrhal, island or film inflammation), widespread (plaques located outside the nasopharynx), toxic (1, 2 and 3 degrees), hypertoxic. It occurs in 90-95% of all cases of the disease.
- Diphtheria croup - localized (larynx), widespread (larynx and trachea), descending (infection spreads to the bronchi).
- Diphtheria of the nose, eyes, skin and genitals.
- A combined form of the disease in which several organs are affected at once.
According to the degree of intoxication of the body, the disease can be of the following forms: nontoxic (caused by nontoxigenic strains of corynebacteria diphtheria), subtoxic, toxic, hemorrhagic and hypertoxic diphtheria.
Clinic and symptoms
Upon contact with patients or carriers of a toxic strain, the probability of infection is about 20%. The first symptoms in the form of fever up to 38–39 ° C, sore throat and difficulty in swallowing appear on the 2nd-10th day.
Since the first symptoms of the most common form of diphtheria with an atypical manifestation are similar to the symptoms of a sore throat, it is recommended at the first signs to pass smears to detect the pathogen. But, in addition to symptoms similar to angina, a typical form of the disease has characteristic signs, which are a specific lesion of the tonsils. The fibrous plaque formed on them forms dense films. Fresh they are easily removed, but as they thicken, a bleeding wound remains when removed. But diphtheria is terrible not with films on the mucous membranes, but with its complications caused by the action of diphtheria toxin.
Possible complications
As the pathogen multiplies, the toxin released becomes more and more and spreads throughout the body with a blood stream. It is the toxin that causes the development of complications, which can be the following:
- Toxic shock.
- Damage to the heart muscle (myocarditis).
- Dystrophic lesions of the kidneys (nephrosis).
- Blood coagulation disorders (DIC - syndrome).
- Damage to the peripheral nervous system (polyneuropathy).
- Croupous manifestations (stenosis of the larynx).
Diagnosis of the disease
The main diagnostic method is microbiological research. For all suspicious tonsillitis, this analysis is assigned to identify corynebacteria. For its implementation, smears are taken from the affected tonsils and the material is placed in a nutrient medium. The analysis lasts 5-7 days and gives an understanding of the toxigenicity of the diphtheria bacillus strain.
An addition to this method is an analysis of antibodies in the blood. There are a lot of methods for carrying out this analysis, but the essence is that if the patient’s blood does not have antibodies to diphtheria toxin, then upon contact with the infection the probability of infection becomes close to 99%.
A non-specific study for diphtheria is a general blood test. It does not confirm or disprove the presence of the pathogen in the body, but only shows the degree of activity of the infectious and inflammatory process in the patient.
Treatment exclusively in the hospital
It is very important to immediately begin treatment of diphtheria, only in this way the likelihood of developing complications is minimal. Patients with a suspected infection are immediately hospitalized in the infectious department. Isolation, bed rest and a full range of therapeutic measures are provided, namely:
- Specific therapy. This is the introduction of antitoxic antidiphtheria serum containing antibodies to the toxin.
- Antibiotic therapy. The use of antibiotics most active against corynebacteria (erythromycin, ceftriaxone and rifampicin).
- A diet whose goal is to reduce the irritability of the mucous membranes of the oropharynx.
Active diphtheria prophylaxis
Protection against this dangerous infectious disease is vaccination. Since the main harm is caused not by diphtheria bacillus itself, but by its toxin, then the toxoid is also vaccinated. In response to its introduction into the body, antibodies are formed specifically to the toxins of the bacterium.
Today, preventive vaccination is carried out by the associated complex vaccines for pertussis, diphtheria and tetanus (DTP). In Russia, several complex vaccines have been registered, including diphtheria toxoid, domestic and imported. Diphtheria toxoid is absolutely harmless, does not cause anaphylactic shock and allergic reactions. In some cases (10%), local allergic reactions in the form of edema, redness of the integument and soreness, which pass by themselves within 2-3 days, may develop. Contraindications to vaccination can be allergic reactions to any component of the complex vaccine, the use of immunosuppressants, immunodeficiency states.
In accordance with the vaccination calendar, children aged 3 to 6 months are vaccinated. Revaccinations are carried out at 1.5 years, at 7 and 14 years. For adults, revaccination every 10 years is recommended.
Natural protection
In favor of vaccination is the fact that after the infection, a person develops a rather unstable immunity, which lasts up to 10 years. After this period, the likelihood of contracting this disease increases. And although repeated diphtheria in many cases is lighter, it is much easier for the patient to tolerate, but the occurrence of intoxication is likely.
Today, vaccination issues raise many questions in society. But in our case, when making a decision, it is worth guided not by emotions, but by facts.
Diphtheria films can clog the airways within 15-30 minutes. Emergency assistance in this case can only be professional - the placement of a tracheostomy tube. Are you ready to risk your life and the life of your loved ones - you choose.