One of the dangerous infectious diseases that is gaining momentum in recent years 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 pathogen toxins - diphtheria corynebacteria. The defeat of the main systems of the body (nervous and cardiovascular) can be quite dangerous, and also lead to sad consequences. About the morphology and microbiology of Corynebacterium diphtheria, their pathogenicity and toxicogenicity, routes of infection, symptoms and treatment of the disease, read in the article
Diphtheria yesterday and today
This disease has been known to mankind since ancient times. It was described in his writings by Hippocrates (460 BC), in the 17th century, diphtheria epidemics mowed down the inhabitants of the cities of Europe, and from the 18th century, the inhabitants of North and South America. The name of the disease (from the Greek Diphthera, which means "film") introduced into medicineFrench pediatrician Armand Trousseau. The causative agent of the disease - the bacterium Corynebacterium diphtheriae - was first discovered in 1883 by the German physician Edwin Klebs. But his compatriot, the microbiologist Friedrich Leffler, isolated the bacterium into a pure culture. The latter belongs to the discovery of a toxin secreted by diphtheria corynebacteria. The first vaccine appeared in 1913 and was invented by Emil Adolf von Behring, a German microbiologist and physician, Nobel laureate in physiology.
Since 1974, the incidence and mortality from diphtheria has declined significantly in all countries that are members of the World He alth Organization, thanks to mass vaccination programs. And if before that in the world more than a million people fell ill every year, and up to 60 thousand died, then after the application of vaccination programs, only isolated cases of outbreaks of diphtheria are recorded. And the greater the percentage of citizens who have undergone preventive vaccinations, the less likely it is that epidemics will occur. Thus, the decrease in vaccination coverage of the CIS population in the 90s led to an outbreak of the disease, when about 160 thousand cases were registered.
Today, according to the he alth authorities, about 50% of the population has been vaccinated against diphtheria, and given that the vaccination schedule involves re-vaccination every 10 years, you can increasingly hear in the media information about a possible epidemiological outbreak of diphtheria in Russia and former CIS countries.
No longerchildhood illness
Diphtheria is an acute, predominantly childhood infectious disease. It is characterized by fibrinous inflammation of the site of localization of the diphtheria bacillus and severe intoxication of the body with its toxins. But over the past 50 years, this disease has “grown up”, and people who are much older than 14 years of age are increasingly suffering from it. In adult patients, diphtheria is a serious disease with a possible fatal outcome.
The most susceptible risk group are children between 3 and 7 years of age. Sources of infection can be sick and he althy 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 diphtheria of the eyes and skin can transmit the infection by contact. In addition, people who do not have external manifestations of the disease, but are carriers of corynebacterium 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 administration, there remains a 20% chance of death, the causes of which are suffocation, toxic shock, myocarditis and respiratory paralysis.
Genus Corynebacterium
The causative agent of diphtheria Corynebacterium diphtheriae (diphtheria bacillus, or Leffler's bacillus) is included in the genus of gram-positivebacteria, which has more than 20 species. Among the 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, a skin infection often found 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 lung abscess, endocarditis.
- Corynebacterium xerosis and Corynebacterium pseudodiphtheriticum - were previously considered to be the causative agents of conjunctivitis and inflammation of the nasopharynx, and today are recognized as saprophytes living on the mucous membranes as part of a different microflora.
The morphology of corynebacteria diphtheria is similar to the morphology of all representatives of this genus. The diphtheria bacillus has a capsule and constrictions (drank). Diphtheria corynebacteria in a smear are rod-shaped and arranged at an angle relative to each other, resembling Roman fives. Among the variety of representatives of this type of bacteria, there are both toxicogenic forms (producing exotoxins with pathogenic influence) and bacteria that do not secrete toxins. However, there is evidence that even non-toxigenic strains of Leffler's sticks contain in the genome the genes responsible for the production of toxins. This means that, under appropriate conditions, these genes canturn 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 boiled for 1 minute.
- On clothes and bedding - after 15 days.
- In the dust they will die in 3-5 weeks.
- When exposed to disinfectants - chloramine, sublimate, carbolic acid, alcohol - in 8-10 minutes.
Mechanism of disease progression
Through the entrance gates (mucous membranes of the tonsils, nose, pharynx, genital organs, skin lesions, conjunctiva), diphtheria corynebacteria enter 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 causative agent of diphtheria are possible:
- Corinebacteria die and the person remains he althy.
- With an insufficient immunity status and high virulence, diphtheria bacilli multiply at the site of invasion and cause a he althy bacteriocarrier.
If there is no antitoxic immunity, toxigenic corynebacterium diphtheria leads to the development of clinical and morphological signs of infection. The toxin penetrates the tissues, lymphatic and circulatory systems, causesvascular paresis and increased permeability of their walls. Fibrinogenic exudate is formed in the intercellular space, necrosis processes develop. As a result of the transformation of fibrinogen into fibrin, films of fibrous plaque appear on the surface of the affected mucous membranes - a characteristic sign of diphtheria. With the blood, the toxin enters the circulatory organs and the nervous system, the adrenal glands and kidneys, and other organs. There it leads to disruption of protein metabolism, cell death and their replacement by connective tissue cells.
Pathogenic toxins
Diphtheria corynebacteria are characterized by high pathogenicity due to the ability to secrete exotoxin, which includes several fractions:
- A neurotoxin that leads to necrosis of mucosal epithelial cells, 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 - increases swelling and permeability of vessel walls.
- Hemolyzing element - leads to the destruction of red blood cells.
These properties of corynebacterium diphtheria, whose task is to spread pathogenic action through toxins throughoutbody, and are the causes of complications in this infection.
Disease classification
Diphtheria is a disease with many forms and manifestations. According to the localization of the invasion, localized and widespread forms of the disease are distinguished.
The shape and variant of the flow are distinguished:
- Diphtheria of the oropharynx - localized (with catarrhal, island or film inflammation), common (raids are located outside the nasopharynx), toxic (1, 2 and 3 degrees), hypertoxic. Occurs in 90-95% of all cases.
- 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: non-toxic (caused by non-toxigenic strains of corynebacterium diphtheria), subtoxic, toxic, hemorrhagic and hypertoxic diphtheria.
Clinic and symptoms
When in 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 days 2-10.
Since the first symptoms of the most common form of diphtheria with atypical presentation are similar to those of a sore throat, it is recommended to take smears at the first signs forpathogen detection. But, in addition to symptoms similar to angina, a typical form of the disease has characteristic signs, which consist in 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 they are 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 it spreads throughout the body with the bloodstream. It is the toxin that causes the development of complications, which may be as follows:
- Toxic shock.
- Affection of the heart muscle (myocarditis).
- Destrophic lesions of the kidneys (nephrosis).
- Blood clotting disorders (DIC - syndrome).
- Injury to the peripheral nervous system (polyneuropathy).
- Croupous manifestations (stenosis of the larynx).
Diagnosis of disease
The main diagnostic method is microbiological examination. With all suspicious tonsillitis, this analysis is prescribed for the identification of 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 for antibodies in the blood. There are many methods for conducting this analysis, but the bottom line is that if in the bloodthe patient does not have antibodies to diphtheria toxin, then contact with the infection, the probability of infection becomes close to 99%.
A non-specific study for diphtheria is a complete blood count. It does not confirm or deny the presence of a 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 begin treatment of diphtheria immediately, only in this way the likelihood of complications is minimal. Patients with suspected infection are immediately hospitalized in the infectious diseases department. Isolation, bed rest and a full range of therapeutic measures are provided, namely:
- Specific therapy. This is an injection of anti-toxic anti-diphtheria serum containing antibodies to the toxin.
- Antibacterial therapy. The use of the most active antibiotics against corynebacteria (erythromycin, ceftriaxone and rifampicin).
- Diet, the purpose of which is to reduce the irritability of the mucous membranes of the oropharynx.
Active prevention of diphtheria
Protection against this dangerous infectious disease is vaccination. Since the main harm is caused not by the diphtheria bacillus itself, but by its toxin, then vaccination is carried out with a toxoid. In response to its introduction into the body, antibodies are formed specifically to the toxins of the bacteria.
Today, preventive vaccination is carried out with associated complex vaccines against whooping cough, diphtheria and tetanus(DTP). In Russia, several complex vaccines, including diphtheria toxoid, of domestic and foreign production, are registered. Diphtheria toxoid is absolutely harmless, does not cause anaphylactic shock and allergic reactions. In some cases (10%), local allergic reactions may develop in the form of swelling, redness of the integument and soreness, which disappear on their own within 2-3 days. Contraindications to vaccination may 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. Repeated revaccinations are carried out at 1.5 years, at 7 and 14 years. For adults, revaccination every 10 years is recommended.
Natural Protection
Vaccination is also supported by the fact that after an infection, a rather unstable immunity is formed in a person, which lasts up to 10 years. After this period, the likelihood of contracting this disease increases. And although repeated diphtheria in many cases is milder, it is much easier for the patient to tolerate, but the occurrence of intoxication is quite likely.
Vaccination issues raise many questions in society today. But in our case, when making a decision, one should be guided not by emotions, but by facts.
Diphtheritic films can block the airways within 15-30 minutes. Emergency assistance in this case can only beprofessional - the imposition of a tracheostomy tube. Are you ready to risk your life and the lives of your loved ones - you choose.
