Pathogenic corynebacteria - F. K

Corynebacteria are gram-positive rod-shaped microorganisms that are widespread in nature and live in the human body. Most representatives of this genus are not pathogenic to humans. Some species cause severe infectious diseases, for example.

The genus Corynebacterium consists of obligate pathogens and agents of typical opportunistic infections. Each type of microorganism has specific biological features and causes various pathologies. Most often the skin and internal organs are affected. When non-sterile catheters are inserted and contaminated prostheses are installed, bacteremia develops.

Corynebacteria - pathogens:

1. Urinary tract infections - urethritis, prostatitis, kidney damage;
2. Respiratory diseases -,;
3. Purulent-septic processes - bacteremia, septicemia, brain abscess, osteomyelitis, endocarditis, septic arthritis,
4. Skin diseases - pseudomycosis;
5. Catheter-associated and wound infections.

Some corynebacteria are representatives of various normocinoses of the human body. They live on the skin, in the upper parts of the respiratory tract, visual analyzer, and urogenital tract. Thus, C. striatum has tropism for the skin, C. durum - for the respiratory epithelium of the respiratory organs, C. glucuronoliticam - for epithelial cells of the genitourinary tract in men. Many species are isolated from environmental objects.

Atoxigenic C. diphtheriae normally colonizes the skin and pharynx without causing disease. Non-pathogenic species of corynebacteria are included in the normocenosis of the large intestine in acceptable quantities. But sometimes these microbes lead to the development of infections and even epidemic outbreaks. This feature is due to the presence of other virulence factors in these microorganisms.

All corynebacteria are conventionally divided into groups:

• Microorganisms dangerous to warm-blooded animals
• Microbes that infect plants
• Opportunistic bacteria that do not cause harm to health.

Children, elderly people and people with immunodeficiency and multiple organ pathologies are most susceptible to the development of infection. In most cases, species identification of corynebacterium spp causes significant difficulties due to their morphobiological characteristics.

Properties of corynebacteria

Corynebacterium diphtheria

Corynebacterium diphtheriae is the causative agent of a dangerous disease for humans - diphtheria. Currently, pathology is recorded extremely rarely and only in certain individuals who, most likely, were not vaccinated in a timely manner.

The spread of infection occurs through airborne droplets or contact during communication with sick people or through infected objects. In case of contamination of food products, the nutritional route becomes relevant. From an epidemiological point of view, healthy bacteria carriers pose the greatest danger.

Depending on the location of the primary focus of infection, there are various shapes diseases. After 7-10 days of incubation, the first clinical signs appear. Fibrinous inflammation develops at the location of the pathological focus. It leads to the destruction of epithelial cells and blood vessels. The gradually formed exudate contains a lot of fibrinogen, which coagulates and forms a plaque on the mucous membrane gray-white color. It adheres tightly to the submucosal layer and cannot be removed. When you try to remove the plaque, bleeding begins. In addition to local signs of inflammation, due to the localization of the entrance gate of the infection, severe intoxication occurs with fever, chills, hyperhidrosis, body aches, lethargy, pale skin, adynamia, hypotension and other signs.

Throat diphtheria is the most dangerous form of infection, which can lead to development, which is fatal. It is caused by swelling of the laryngeal mucosa and severe asphyxia.

The main diagnostic method for diphtheria is microbiological. If dense fibrin films and swelling of the pharynx or other parts of the body appear, it is necessary to take a smear from the patient for diphtheria and begin this study. Throat discharge, mucus from the nose, plaque from the tonsils - biomaterial that is delivered to the bacteriological laboratory for analysis. It is inoculated on media containing serum or blood with potassium tellurite, which inhibits the growth of secondary microflora. After incubation, the grown colonies are examined under a microscope, a pure culture is accumulated, and final identification to species is carried out. The results of sero- and phage typing are important for clinicians. Determining the toxigenicity of an isolated culture has important diagnostic value.

Etiotropic therapy for diphtheria consists of administering antitoxic serum, antibiotics and sulfonamides to patients. Symptomatic and pathogenetic therapy improves the general condition of patients, relieving them of symptoms. After the acute symptoms of pathology have been relieved, sanitizing physiotherapy procedures are indicated - ultrasound and laser therapy directly on the lesion.

To prevent the development of such a serious disease as diphtheria, universal immunization of the population is carried out with the DPT vaccine in accordance with the National Vaccination Calendar. Mass vaccination has now significantly reduced diphtheria incidence and mortality rates.

Corynebacterium non diphtheriae are inhabitants of the external environment. They are found on the skin and mucous membranes internal organs, being representatives of normocenoses. In weakened individuals at risk, these microbes can cause inflammatory processes that are as severe as diseases caused by unconditional pathogens. In order to correctly select etiotropic therapy and cure the patient, it is necessary to accurately and quickly identify the microbe.

Corynebacterium glucuronolyticum

Corynebacterium glucuronolyticum - microorganisms isolated from people with diseases of the genitourinary system. They are causative agents of prostatitis and urethritis in men, but can live in optimal quantities in the body of healthy people, being representatives of this biocinosis.

Under the influence of negative factors, Corynebacterium glucuronolyticum actively grows and reproduces. Bacteria begin to acquire pathogenic properties, causing local inflammation. The prostate parenchyma swells, increases in size, and is infiltrated with lymphocytes. Inflammation spreads to the periglandular tissue, the structure of the organ changes, epithelial cells are destroyed, and the secretory function of the gland is lost.

Diphtheroids are part of the normocinosis of the urogenital tract of men along with staphylococci, enterococci, single mycoplasmas and ureaplasmas. During sexual activity, the urethra becomes colonized with potential uropathogenic bacteria. With hypothermia, nervous overstrain, and prolonged use of antibiotics, inflammation occurs in the prostate caused by opportunistic bacteria. In this case, the functions of local body defense factors are disrupted.

Patients with prostatitis or urethritis caused by Corynebacterium glucuronolyticum complain of pain in the perineum, scrotum, penis, intensifying at the end of urination; dysuric disorders: polyuria, nocturia, incomplete emptying of the bladder, weak stream; sexual weakness - erection and ejaculation disorders.

Diagnostic measures:

• Palpation of the prostate gland per rectum - changes in the size of the gland, heterogeneous consistency, alternation of dense and soft areas, painful sensations. The hemogram shows signs of inflammation.
• Bacteriological examination of urine and prostate secretions is carried out in a microbiological laboratory. The biomaterial is inoculated on standard media for primary identification, the grown colonies are examined microscopically, and then the structure, physiology, enzymatic and biochemical activity of the isolated pathogen is studied. Corynebacterium glucuronolyticum grows well on blood agar. After 24 hours, convex colonies of a whitish-yellowish hue without zones of hemolysis appear on it.
• PCR diagnostics - determination of the genetic material of corynebacteria in the test sample.

Treatment of prostatitis and urethritis is antimicrobial. Patients are prescribed fluoroquinolones, macrolides and tetracyclines.

Corynebacterium glucuronolyticum is a causative agent of diseases of the urogenital tract in men. Today, infectious prostatitis and urethritis are quite common ailments and a serious medical problem. Specific diagnostic methods and therapeutic principles remain not fully understood. Patients, having “earned” such an illness, suffer all their lives. Only effective antimicrobial treatment will help them cope with the pathology.

Diphtheroids are microorganisms from the genus Corynebacterium, which are currently poorly studied. This microbe, which has another name, is one of them - Hofmann's bacillus. Corynebacterium received it in honor of its discoverer.

Corynebacterium pseudodiphtheriticum

Diphtheroids are ubiquitous: they are found in the air, soil, water, and on foods. Microbes are resistant to environmental factors - temperature, sunlight, humidity. Chloramine and other chlorine-containing disinfectants destroy them in a couple of minutes. Diphtheroids live in various biocenoses of a healthy human body - in the nasopharynx, on the skin, in the urethra, genitals, sperm.

Signs that distinguish this species from pathogenic corynebacteria:

1. Lack of volutin
2. Chaotic arrangement in the smear,
3. Massive growth on simple nutrient media at 37 degrees.

Corynebacterium pseudodiphtheriticum causes purulent-inflammatory processes when the macroorganism is weakened by viral infections, stress, oncopathologies, and secondary immunodeficiency. In this case, the disease does not develop in places where bacteria usually live. They are not capable of toxin formation. Penetrating into the blood, corynebacteria contribute to the development of bacteremia. There are known cases of severe bronchitis and pneumonia due to prolonged immunosuppression. These microbes can cause endocarditis, lymphadenitis, dermatological diseases, and urinary tract infections.

Dysbiotic changes develop in the body when the number of diphtheroids increases to 10 to 5 or 6 degrees of microbial cells. In this case, characteristic clinical manifestations arise.

Treatment of diseases caused by Corynebacterium pseudodiphtheriticum involves the use of bacteriophages, antibiotics, carrying out plasmapheresis and other methods of blood purification.

If diphtheroids have been isolated from blood, cerebrospinal fluid, urine and other sterile substrates, they should be considered as potential pathogens and treated accordingly. In a microbiological laboratory, a test is performed to determine the sensitivity of the isolated microbe to antibiotics.

Video: lecture - corynebacteria, stages of diphtheria infection

Corynebacteria. Bordetella.

The causative agent of diphtheria - Corynebacterium diphtheriae and a large group of microorganisms of the genus Corynebacterium that are similar in morphological and biochemical properties are called coryneform bacteria or diphtheroids. They are represented by gram-positive, motionless rods, often with thickenings at the ends, reminiscent of a club (coryne - club). Diphtheroids are widely distributed in soil, air, and food products (milk). Among them, three ecological groups can be distinguished:

Pathogens of humans and animals;

Plant pathogens;

Non-pathogenic corynebacteria.

Many types of diphtheroids are normal inhabitants of the skin, mucous membranes of the pharynx, nasopharynx, eyes, respiratory tract, urethra and genitals.

Diphtheria- an acute infectious disease mainly of childhood, which is characterized by intoxication of the body with diphtheria toxin and characteristic fibrinous (diphtheritic) inflammation at the site of localization of the pathogen (phther - film).

Morphological and tinctorial properties. C.diphtheriae are thin polymorphic rods with club-shaped ends, often containing volutinous inclusions, revealed by methylene blue or Neisser staining. With the latter, the sticks are colored yellow-straw, the grains of volutin (polymetaphosphate) are dark brown. In cultures, the sticks are at an angle to each other (features of division), forming various figures - spread fingers, V, Y, L, etc. They have a microcapsule and fimbriae that facilitate adhesion to the epithelium of the mucous membranes.

Cultural properties. Diphtheria root bacteria do not grow on simple media. They require media with blood or blood serum (Leffler's, Roux's media), on which growth is observed after 10-12 hours, during which time the accompanying (contaminating samples) microflora does not have time to fully develop.

The most optimal are tellurite medium and tellurite - McLeod's chocolate agar. High concentrations of potassium tellurite in these environments inhibit the growth of foreign flora. Corynebacterium diphtheria reduces tellurite to metallic tellurium, which gives its colonies a dark gray or black color.

This pathogen has biotypes - gravis, mitis, intermedius, which differ in morphology, antigenic and biochemical properties, and the severity of diseases in humans. The gravis type often causes outbreaks and a more severe course, and is characterized by large, daisy-shaped colonies with jagged edges and radial striations (R-form). The mitis type causes predominantly mild sporadic diseases and forms small, smooth colonies with smooth edges (S-forms) on dense media. The intermedius type occupies an intermediate position and forms on dense media RS-forms that are transitional in characteristics, but even smaller. In liquid media they cause turbidity of the media and form a crumbly precipitate.

Biochemical properties. Corynebacterium diphtheria ferments glucose and maltose. The lack of activity towards sucrose and urea is an important differential feature among diphtheroids. They have cystenase activity (break down cysteine) - Pisu test.

Antigenic structure. O- and K-antigens are isolated. The polysaccharide components of cell wall O-antigens have intergeneric properties, causing nonspecific cross-reactions with mycobacteria and actinomycetes (nocardia).

Surface K-antigens are capsular proteins that are species specific and immunogenic. There are 11 serotypes. Serotypes 1-5 and 7 belong to biovar gravis. Serotyping of cultures is carried out in the Republic of Armenia with diagnostic sera for the corresponding serovars and polygroup agglutinating serum.

In serological diagnosis in humans, RPGA, which is more sensitive than RA, is often used. Currently, ELISA is also used. Many strains of Corynebacterium diphtheria (especially non-toxigenic ones) have spontaneous agglutinability and polyagglutinability.

Pathogenicity factors. Toxigenic strains of the causative agent of diphtheria produce a strong exotoxin (heat-labile, highly toxic immunogenic protein). Nontoxigenic strains do not cause disease.

The toxin causes irreversible blocking of polypeptide chain elongation, i.e. any protein synthesis. Mainly certain systems are affected: sympathetic-adrenal, heart and blood vessels, peripheral nerves. There are structural and functional disorders of the myocardium, demyelination of nerve fibers, leading to paralysis and paresis.

The ability to form toxins is exhibited only by lysogenic strains infected with a bacteriophage (beta phage) carrying the tox gene, which encodes the structure of the toxin (i.e., carrying temperate prophage genes on their chromosome). Phage typing is used to differentiate strains of Corynebacterium diphtheria.

Epidemiology. The reservoir is a person (patient, convalescent, bacteria carrier). The main route of transmission is airborne droplets, seasonality is autumn - winter. The pathogen is well preserved at low temperatures, in a dried state (saliva, mucus, dust).

Clinical and pathogenetic features. The pathogen at the site of penetration causes fibrinous inflammation with the formation of a fibrinous film tightly fused to the tissues. The effect of exotoxin is essential in the pathology caused (described in the section “pathogenicity factors”). According to localization, diphtheria is distinguished from the oropharynx (most often), respiratory tract, nose and rare localization (eyes, external genitalia, skin, wound surface). Diphtheria of the pharynx can cause croup and asphyxia.

Laboratory diagnostics. The main diagnostic method is bacteriological. Used to identify patients, bacteria carriers, and contacts. Sterile swabs are used to take material for microscopy and culture - mucus from the throat and nose, films from the tonsils and other places suspected of diphtheritic lesions.

The pathogen is isolated by inoculation on selective tellurite media and blood agar. On the mucous membrane of the eye, C. xerosis is often detected (a possible cause of chronic conjunctivitis), in the nasopharynx - C. pseudodiphtheriticum (Hofmann's bacillus), and other diphtheroids are also detected.

To differentiate the causative agent of diphtheria from diphtheroids, indicators such as the ability to reduce tellurite and form dark colonies, the Pisa test, fermentation of carbohydrates (glucose, maltose, sucrose) and urea, and the ability to grow in anaerobic conditions (characteristic of the causative agent of diphtheria) are used.

An obligatory step is to determine the toxigenicity of the culture. The most common methods are bioassays on guinea pigs and the agar precipitation reaction. ELISA with antitoxin, genetic probes and PCR are also used to detect fragment A of the tox gene.

Treatment. Antitoxic diphtheria serum, antibiotics and sulfonamide drugs are used.

Post-infectious immunity is persistent, predominantly antitoxic. To quantitatively determine the level of antitoxic immunity, the Schick test (intradermal injection of a toxin) was previously used, now - RPGA with an erythrocyte diagnosticum obtained by sensitizing erythrocytes with diphtheria toxoid.

Prevention. The basis is mass immunization of the population. Various drugs containing diphtheria toxoid are used - DTP, ADS, ADS-M, AD and AD-M.

Corynebacterium diphtheriae (causative agent of diphtheria) - was discovered for the first time in 1883 by E. Klebs in film sections, obtained in pure culture in 1884 by F. Leffler. In 1888, E. Roux and A. Yersen discovered its ability to produce an exotoxin, which plays a major role in the etiology and pathogenesis of diphtheria. The production of antitoxic serum by E. Bering in 1892 and its use since 1894 for the treatment of diphtheria made it possible to significantly reduce mortality. A successful attack on this disease began after 1923 in connection with the development of a method for obtaining diphtheria toxoid by G. Rayon. Corynebacterium diphtheriae belongs to the genus Corynebacterium (class Actinobacteria). Morphologically, it is characterized by the fact that the cells are club-shaped thickened at the ends (Greek sogupe - club), form branching, especially in old cultures, and contain granular inclusions.

Diphtheria is an acute infectious disease, mainly of childhood, which is manifested by deep intoxication of the body with diphtheria toxin and characteristic fibrinous inflammation at the site of localization of the pathogen. The name of the disease comes from the Greek word diphthera - skin, film, since a dense, grayish-white film is formed at the site of the pathogen's reproduction.

The genus Corynebacterium includes big number species, which are divided into three groups.

Corynebacteria, pathogenic for plants.

Non-pathogenic corynebacteria. Many species of corynebacteria are normal inhabitants of the skin, mucous membranes of the pharynx, nasopharynx, eyes, respiratory tract, urethra and genitals.

Morphology of corynebacteria

C. diphtheriae - straight or slightly curved, motionless rods 1.0-8.0 µm long and 0.3-0.8 µm in diameter; they do not form spores or capsules. Very often they have swellings at one or both ends, often contain metachromatic granules - grains of volutin (polymetaphosphates), which, when stained with methylene blue, acquire a bluish-purple color. To detect them, a special Neisser staining method has been proposed. In this case, the rods are colored straw-yellow, and the volutin grains are dark brown, and are usually located at the poles. Corynebacterium diphtheriae stains well with aniline dyes and is Gram-positive, but in old cultures it is often discolored and has a negative Gram stain. It is characterized by pronounced polymorphism, especially in old cultures and under the influence of antibiotics. The G + C content in DNA is about 60 mol%.

Biochemical properties of corynebacteria

The diphtheria bacillus is an aerobe or facultative anaerobe, the optimum temperature for growth is 35-37 ° C (growth limits 15-40 ° C), the optimal pH is 7.6-7.8. It is not very demanding on nutrient media, but grows better on media containing serum or blood. Collapsed serum Roux or Leffler media are selective for diphtheria bacteria; growth on them appears after 8-12 hours in the form of convex, pinhead-sized colonies of grayish-white or yellowish-cream color. Their surface is smooth or slightly granular; on the periphery the colonies are somewhat more transparent than in the center. The colonies do not merge, as a result of which the culture takes on the appearance of shagreen leather. In the broth, growth manifests itself in the form of uniform cloudiness, or the broth remains transparent, and a delicate film forms on its surface, which gradually thickens, crumbles and settles in flakes to the bottom.

A feature of diphtheria bacteria is their good growth on blood and serum media containing such concentrations of potassium tellurite that inhibit the growth of other types of bacteria. This is due to the fact that C. diphtheriae reduces potassium tellurite to metallic tellurium, which, when deposited in microbial cells, gives the colonies a characteristic dark gray or black color. The use of such media increases the percentage of inoculation of diphtheria bacteria.

Corynebacterium diphtheriae ferment glucose, maltose, galactose with the formation of acid without gas, but do not ferment (as a rule) sucrose, have cystinase, do not have urease and do not form indole. According to these characteristics, they differ from those coryneform bacteria (diphtheroids), which are most often found on the mucous membrane of the eye (Corynebacterium xerosus) and nasopharynx (Corynebacterium pseiidodiphtheriticum) and from other diphtheroids.

In nature, there are three main variants (biotypes) of diphtheria bacillus: gravis, intermedins and mitis. They differ in morphological, cultural, biochemical and other properties.

The division of diphtheria bacteria into biotypes was made taking into account the forms of diphtheria in patients with which they are isolated with the greatest frequency. The gravis type is often isolated from patients with severe diphtheria and causes cluster outbreaks. The mitis type causes milder and sporadic cases of disease, while the intermedius type is intermediate between the two. Corynebacterium belfanti, previously assigned to the mitis biotype, has been separated into an independent, fourth biotype. Its main difference from the biotypes gravis and mitis is the ability to reduce nitrates to nitrites. Strains of Corynebacterium belfanti have pronounced adhesive properties, and among them both toxigenic and non-toxigenic variants are found.

Antigenic structure of corynebacteria

Corynebacteria are very heterogeneous and mosaic. Several dozen somatic antigens have been found in diphtheria pathogens of all three types, according to which they are divided into serotypes. In Russia, a serological classification has been adopted, according to which 11 serotypes of diphtheria bacteria are distinguished, of which 7 main (1-7) and 4 additional, rare serotypes (8-11). Six serotypes (1, 2, 3, 4, 5, 7) belong to the gravis type, and five (6,8,9,10,11) belong to the mitis type. The disadvantage of the serotyping method is that many strains, especially non-toxigenic ones, exhibit spontaneous agglutination or polyagglutinability.

Phage typing of Corynebacterium diphtheriae

To differentiate diphtheria bacteria, various phage typing schemes have been proposed. According to the scheme of M.D. Krylova, using a set of 9 phages (A, B, C, D, F, G, H, I, K), it is possible to type the majority of toxigenic and non-toxigenic strains of the gravis type. Taking into account the sensitivity to these phages, as well as cultural, antigenic properties and the ability to synthesize coricins (bactericidal proteins), M. D. Krylova identified 3 independent groups of corynebacteria of the gravis type (I-III). Each of them contains subgroups of toxigenic and their non-toxigenic analogues of diphtheria pathogens.

Resistance of corynebacteria

Corynebacterium diphtheriae exhibits greater resistance to low temperatures, but quickly dies at high temperatures: at 60 ° C - within 15-20 minutes, when boiling - after 2-3 minutes. All disinfectants (Lysol, phenol, chloramine, etc.) in the usually used concentration destroy it in 5-10 minutes. However, the causative agent of diphtheria tolerates drying well and can remain viable for a long time in dried mucus, saliva, and dust particles. In a fine aerosol, diphtheria bacteria remain viable for 24-48 hours.

Pathogenicity factors

The pathogenicity of Corynebacterium diphtheriae is determined by the presence of a number of factors.

Factors of adhesion, colonization and invasion

The structures responsible for adhesion have not been identified, but without them the diphtheria bacillus would not be able to colonize cells. Their role is played by some components of the pathogen’s cell wall. The invasive properties of the pathogen are associated with hyaluronidase, neuraminidase and protease.

A toxic glycolipid contained in the cell wall of the pathogen. It is a 6,6"-diester of trehalose containing corynemycolic acid (C32H6403) and corynemycolic acid (C32H62O3) in equimolar ratios (trehalose-6,6"-dicorynemycolate). The glycolipid has a destructive effect on tissue cells at the site of pathogen reproduction.

An exotoxin that determines the pathogenicity of the pathogen and the nature of the pathogenesis of the disease. Nontoxigenic variants of C. diphtheriae do not cause diphtheria.

The exotoxin is synthesized in the form of an inactive precursor - a single polypeptide chain with mm. 61 kD. Its activation is carried out by its own bacterial protease, which cuts the polypeptide into two peptides linked by disulfide bonds: A (mw 21 kDa) and B (mw 39 kDa). Peptide B performs an acceptor function - it recognizes the receptor, binds to it and forms an intramembrane channel through which peptide A penetrates the cell and realizes the biological activity of the toxin. Peptide A is an ADP-ribosyltransferase enzyme that transfers adenosine diphosphate ribose from NAD to one of the amino acid residues (histidine) of the protein elongation factor EF-2. As a result of modification, EF-2 loses its activity, and this leads to suppression of protein synthesis by ribosomes at the translocation stage. The toxin is synthesized only by C. diphtheriae that carry the genes of a moderate converting prophage on their chromosome. The operon encoding the synthesis of the toxin is monocistronic, it consists of 1.9 thousand base pairs and has a toxP promoter and 3 sections: toxS, toxA and toxB. The toxS region encodes 25 amino acid residues of the signal peptide (it ensures the release of the toxin through the membrane into the periplasmic space of the bacterial cell), toxA - 193 amino acid residues of peptide A, and toxB - 342 amino acid residues of peptide B of the toxin. The loss of a prophage by a cell or mutations in the tox operon make the cell low-toxigenic. In contrast, lysogenization of nontoxigenic C. diphtheriae by converting phage converts them into toxigenic bacteria. This has been proven unequivocally: the toxigenicity of diphtheria bacteria depends on their lysogenization by converting tox-corynephages. Corynephages are integrated into the chromosome of corynebacteria using the mechanism of site-specific recombination, and strains of diphtheria bacteria can contain 2 recombination sites (attB) in their chromosomes, and corynephages are integrated into each of them with the same frequency.

Genetic analysis of a number of non-toxigenic strains of diphtheria bacteria, carried out using labeled DNA probes carrying fragments of the corynephage tox operon, showed that their chromosomes contain DNA sequences homologous to the corynephage tox operon, but they either encode inactive polypeptides or are located in “ silent" state, i.e. inactive. In this regard, a very important epidemiologically important question arises: can non-toxigenic diphtheria bacteria turn into toxigenic ones under natural conditions (in the human body), similar to what happens in vitro? The possibility of such a transformation of nontoxigenic cultures of corynebacteria into toxigenic ones using phage conversion was shown in experiments on guinea pigs, chicken embryos and white mice. However, whether this happens during the natural epidemic process (and if it happens, how often) has not yet been established.

Due to the fact that diphtheria toxin in the body of patients has a selective and specific effect on certain systems (mainly the sympathetic-adrenal system, heart, blood vessels and peripheral nerves are affected), it is obvious that it not only inhibits protein biosynthesis in cells, but also causes other disturbances in their metabolism.

The following methods can be used to detect the toxigenicity of diphtheria bacteria:

Biological tests on animals. Intradermal infection of guinea pigs with the filtrate of a broth culture of diphtheria bacteria causes necrosis at the injection site. One minimal lethal dose of toxin (20-30 ng) kills a 250 g guinea pig when administered subcutaneously on days 4-5. The most characteristic manifestation of the action of the toxin is damage to the adrenal glands; they are enlarged and sharply hyperemic.

Infection of chicken embryos. Diphtheria toxin causes their death.

Infection of cell cultures. Diphtheria toxin causes a distinct cytopathic effect.

Enzyme-linked immunosorbent assay method using peroxidase-labeled antitoxins.

Using a DNA probe to directly detect the tox operon in the chromosome of diphtheria bacteria.

However, the simplest and most common way to determine the toxigenicity of diphtheria bacteria is serological - the gel precipitation method. Its essence is as follows. A strip of sterile filter paper measuring 1.5 x 8 cm is moistened with antitoxic diphtheria serum containing 500 AE in 1 ml and applied to the surface of the nutrient medium in a Petri dish. The cup is dried in a thermostat for 15-20 minutes. The test cultures are sown with plaques on both sides of the paper. Several strains are inoculated onto one plate, one of which, known to be toxigenic, serves as a control. The inoculated dishes are incubated at 37 °C, the results are taken into account after 24-48 hours. Due to counter diffusion of the antitoxin and toxin in the gel, a clear precipitation line is formed at the site of their interaction, which merges with the precipitation line of the control toxigenic strain. Stripes of nonspecific precipitation (they are formed if, in addition to the antitoxin, other antimicrobial antibodies are present in small quantities in the serum) appear late, are weakly expressed and never merge with the precipitation strip of the control strain.

Post-infectious immunity

Durable, persistent, virtually lifelong, repeated cases of the disease are rare - in 5-7% of those who have recovered from the disease. is mainly antitoxic in nature, antimicrobial antibodies are of lesser importance.

To assess the level of anti-diphtheria immunity, the Schick test was previously widely used. For this purpose, children were injected intradermally with 1/40 Dim guinea pig toxin in a volume of 0.2 ml. In the absence of antitoxic immunity, after 24-48 hours, redness and swelling with a diameter of more than 1 cm appear at the injection site. Such a positive Schick reaction indicates either the complete absence of antitoxin, or that its content is less than 0.001 AE/ml of blood. A negative Schick reaction is observed when the antitoxin content in the blood is above 0.03 AU/ml. When the antitoxin content is below 0.03 AE/ml, but above 0.001 AE/ml, the Schick reaction can be either positive or, sometimes, negative. In addition, the toxin itself has a pronounced allergenic property. Therefore, to determine the level of anti-diphtheria immunity (quantitative content of antitoxin), it is better to use RPGA with an erythrocyte diagnosticum sensitized with diphtheria toxoid.

Epidemiology of diphtheria

The only source of infection is a person - a sick person, a recovering person, or a carrier of the bacteria. Infection occurs through airborne droplets, airborne dust, and also through various objects that were used by sick or healthy bacteria carriers: dishes, books, linen, toys, etc. In case of contamination of food products (milk, creams, etc.) etc.) infection through nutritional routes is possible. The most massive release of the pathogen occurs in the acute form of the disease. However, those with subtle, atypical forms of the disease are of greatest epidemiological importance, since they are often not hospitalized and are not identified immediately. A patient with diphtheria is contagious during the entire period of illness and part of the recovery period. The average period of bacterial carriage in convalescents varies from 2 to 7 weeks, but can last up to 3 months.

Bacteria carriers play a special role in the epidemiology of diphtheria. In conditions of sporadic morbidity, they are the main distributors of diphtheria, contributing to the preservation of the pathogen in nature. The average duration of carriage of toxigenic strains is slightly shorter (about 2 months) than for non-toxigenic strains (about 2-3 months).

The reason for the formation of carriage of toxigenic and non-toxigenic diphtheria bacteria is not fully understood, since even a high level of antitoxic immunity does not always ensure complete liberation of the body from the pathogen. The level of antibacterial immunity may be of some importance. The carriage of toxigenic strains of diphtheria bacteria is of primary epidemiological importance.

Diphtheria symptoms

People of any age are susceptible to diphtheria. The pathogen can enter the human body through the mucous membranes of various organs or through damaged skin. Depending on the location of the process, diphtheria of the pharynx, nose, larynx, ear, eye, genital organs and skin is distinguished. Mixed forms are possible, for example diphtheria of the pharynx and skin, etc. The incubation period is 2-10 days. With a clinically pronounced form of diphtheria, a characteristic fibrinous inflammation of the mucous membrane develops at the site of localization of the pathogen. The toxin produced by the pathogen first affects epithelial cells and then nearby blood vessels, increasing their permeability. The escaping exudate contains fibrinogen, the coagulation of which leads to the formation of grayish-white filmy deposits on the surface of the mucous membrane, which are tightly fused to the underlying tissue and, when separated from it, cause bleeding. The consequence of damage to blood vessels may be the development of local edema. Diphtheria of the pharynx is especially dangerous, since it can cause diphtheria croup due to swelling of the mucous membrane of the larynx and vocal cords, which previously killed 50-60% of children with diphtheria as a result of asphyxia. Diphtheria toxin, entering the blood, causes general deep intoxication. It primarily affects the cardiovascular, sympathetic-adrenal systems and peripheral nerves. Thus, the symptoms of diphtheria consist of a combination of local signs, depending on the location of the entrance gate, and general symptoms caused by toxin poisoning and manifested in the form of adynamia, lethargy, pallor of the skin, low blood pressure, myocarditis, peripheral nerve paralysis and other disorders. Diphtheria in vaccinated children, if observed, is usually mild and without complications. Mortality in the period before the use of serotherapy and antibiotics was 50-60%, now it is 3-6%.

Laboratory diagnosis of diphtheria

The only reliable method for microbiological diagnosis of diphtheria is bacteriological, with mandatory testing of the isolated culture of corynebacteria for toxigenicity. Bacteriological tests for diphtheria are carried out in three cases:

for the diagnosis of diphtheria in children and adults with acute inflammatory processes in the pharynx, nose, nasopharynx;

according to epidemic indications of persons who were in contact with the source of the causative agent of diphtheria;

persons newly entering orphanages, nurseries, boarding schools, and other special institutions for children and adults, in order to identify possible diphtheria bacillus bacteria carriers among them.

The material for research is mucus from the throat and nose, film from the tonsils or other mucous membranes, which are the site of entry for the pathogen. Inoculations are carried out on tellurite serum or blood media and at the same time on coagulated serum media Roux (coagulated horse serum) or Leffler (3 parts bovine whey + 1 part sugar broth), on which the growth of corynebacteria appears within 8-12 hours. The isolated culture is identified by a set of morphological, cultural and biochemical properties; whenever possible, sero- and phage typing methods are used. In all cases, testing for toxigenicity using one of the above methods is mandatory. The morphological features of corynebacteria are best studied using three methods of staining a smear: Gram, Neisser and methylene blue (or toluidine blue).

Treatment of diphtheria

A specific treatment for diphtheria is the use of anti-diphtheria antitoxic serum containing at least 2000 IU per 1 ml. The serum is administered intramuscularly in doses from 10,000 to 400,000 IU, depending on the severity of the disease. An effective treatment method is the use of antibiotics (penicillins, tetracyclines, erythromycin, etc.) and sulfonamide drugs. To stimulate the production of your own antitoxins, you can use toxoid. To free yourself from bacterial carriage, you should use those antibiotics to which this strain of corynebacteria is highly sensitive.

Specific prevention of diphtheria

The main method of combating diphtheria is mass routine vaccination of the population. For this purpose, various vaccine options are used, including combined ones, i.e., aimed at simultaneously creating immunity against several pathogens. The most widely used vaccine in Russia is the DTP vaccine. It is a suspension of pertussis bacteria killed by formalin or merthiolate (20 billion per 1 ml) adsorbed on aluminum hydroxide and contains diphtheria toxoid in a dose of 30 flocculating units and 10 binding units of tetanus toxoid per 1 ml. Children are vaccinated from 3 months of age, and then revaccinations are carried out: the first after 1.5-2 years, subsequent ones at the ages of 9 and 16 years, and then every 10 years.

Thanks to mass vaccination, which began in the USSR in 1959, the incidence of diphtheria in the country by 1966 was reduced by 45 times compared to 1958, and its rate in 1969 was 0.7 per 100,000 population. What followed in the 80s. XX century the decline in vaccinations has led to dire consequences. In 1993-1996 Russia was swept by a diphtheria epidemic. Adults, mostly those who had not received vaccinations, and children were sick. In 1994, almost 40 thousand patients were registered. In this regard, mass vaccination was resumed. During this period, 132 million people were vaccinated, including 92 million adults. In 2000-2001 The coverage of children with vaccinations on time was 96%, and with revaccination - 94%. Thanks to this, the incidence of diphtheria in 2001 decreased by 15 times compared to 1996. However, in order to bring the incidence rate to isolated cases, it is necessary to cover at least 97-98% of children in the first year of life with vaccination and ensure mass revaccination in subsequent years. It is hardly possible to achieve complete elimination of diphtheria in the coming years due to the widespread carriage of toxigenic and non-toxigenic diphtheria bacteria. Solving this problem will also take some time.

The genus Corynebacterium diphtheriae includes the pathogen diphtheriae and opportunistic corynebacteria. pseudodiphtheria corynebacteria C. pseudodiphtheriticum, C. xerosis and C. ulcerans, living in the human body.

Corynehactcrium diphtheriae was discovered in 1883 by E. Clsbs. isolated in 1884 by F. Leffler.

Morphology, cultural, biochemical properties. Corynebacteria diphtheria are thin, slightly curved gram-positive rods 1-5 µm long; they do not form flagella, spores or capsules. Characteristic morphological features of these bacteria: club-shaped thickenings at the ends in which volutin grains are located, the arrangement of rods in the iodine smear at an angle to each other, in the form of the letter V. Volutin grains are detected by staining with Leffler's blue (they are stained more intensely than the body of the bacterium) or according to Psysser (the body of the bacterium is painted yellow, the grains of the bacterium are dark blue) (color insert in Fig. 34).

Facultative anaerobe. The optimal temperature for growth is 37°C, pH 7.6. Grows on special nutrient media: on elective medium - coagulated whey, on Clauberg's medium. containing coagulated whey and potassium tellurite. Depending on the biological properties, biovars of diphtheria bacilli are distinguished: biovar gravis bacilli form large gray colonies on Clauberg’s medium with jagged edges, radial striations, reminiscent of a daisy flower; biovar mitis - small, black, convex colonies with smooth edges; intermedius - colonies of an intermediate type. The gravis type has the greatest virulence. Growth on beveled rolled whey is characteristic - even with abundant sowing, continuous growth does not form, colonies do not merge, growth resembles a cobblestone street or shagreen leather.

Differences in the enzymatic properties of individual corynebacterium species are used to differentiate them (Table 10).

Antigens. Based on O-antigen, C. diphtheriae is divided into 11 serovars. Factors of pathogenicity. The main property of the causative agent of diphtheria

Toxigenicity. The exotoxin of the diphtheria bacillus causes a local inflammatory reaction and general intoxication of the body with damage to the adrenal glands, myocardium, and nervous system. There are toxigenic and non-toxigenic strains of C. diphtheriae. Diphtheria is caused by toxigenic strains. The ability to produce exotoxin is associated with the presence in the cell of a prophage carrying the tox + gene, responsible for the synthesis of the toxin.

The strength of the toxin is measured in Dim - the smallest amount of toxin that kills a guinea pig weighing 250 g within 3-4 days. The toxin of all diphtheria bacilli is antigenically identical; there are no serotypes.

In addition to the toxin, Corynebacterium diphtheria produces enzymes: hyaluronidase, neuraminidase, fibrinolysin, which ensure their distribution in tissues, but bacteremia is not clinically manifested.

Sustainability. Diphtheria bacilli are resistant to drying and low temperatures. When children's toys get on dishes with saliva and films, they can remain there for a long time. They are sensitive to disinfectants and die immediately when boiled.

Disease in humans. The source of infection is sick people and carriers. The main route of transmission is airborne droplets, but contact and household contact is also possible - through dishes and toys. Diseases occur in individuals who do not have antitoxic immunity. In persons who have antitoxic immunity, in the absence of antimicrobial immunity against corynebacterin diphtheria, carriage of these pathogens may develop, localized on the mucous membrane of the pharynx or nose.

The incubation period of the disease is 2-10 days. At the site of penetration, inflammation develops and a diphtheritic film is formed. The exotoxin enters the blood and toxinemia develops. Clinical forms of diphtheria: diphtheria of the pharynx (85-90% of all cases), nose, larynx, eyes, external genitalia, skin, wounds, etc.

Immunity. After the illness we have a strong antitoxic immunity, but repeated cases are still observed. The level of antitoxin in the blood can be determined using RNGA with erythrocyte diapusticum, containing erythrocytes with diphtheria toxoid adsorbed on them.

Laboratory diagnostics. Early diagnosis is important in order to begin treatment in a timely manner. The material for research is taken from the affected areas using two sterile cotton swabs. When testing for carriage, mucus is taken from the throat and nose. It is very important to send the material to the laboratory immediately.

One of the swabs is used for culture, and with the other swab they make smears for microscopic examination, but this will rarely give a positive result. The main thing is a bacteriological study - inoculation on a plate with a nutrient medium, examination of grown colonies: smears, study of morphology, determination of toxigenicity by precipitation in agar with antitoxic serum. The species C. diphhlheriae is determined by biochemical properties. The results of the bacteriological study indicate: “toxigenic C. diphtheriae has been isolated” or “non-toxigenic C. diphtheriae has been isolated.” Since the effectiveness of treatment depends on the earliest possible start, an accelerated method of detecting diphtheria toxin directly in the test material is used using the RIGA delay reaction. Reaction principle: the test material in different dilutions is added to a certain amount of antitoxic serum, then an erythrocyte diagnostic kit containing diphtheria toxoid is added. In the control (without the test material), the antitoxic serum causes agglutination of erythrocytes. If the test material contains a toxin, it combines with the serum and causes PHHA retention.

Preventive and therapeutic drugs. The main importance in the prevention of diphtheria is active immunization, which is carried out, starting from the age of three months, with a vaccine containing diphtheria toxoid: DTP, ADS. In the future, revaccination is carried out for children, and then for adults. Contraindications to vaccinations are very limited.

There are vaccines with a reduced content of antigens: DTP-m, ADS-m, AD-m. used for immunization of people for whom the full dose of vaccine is contraindicated.

For the treatment of patients, early specific serotherapy with antitoxic diphtheria serum using doses depending on the localization of the process is most important. The serum is administered using the Bezredka method. At the same time, antibiotic therapy (benzylpenicillin, erythromycin, rifampicin, etc.) is carried out.

Diphtheria is an acute infectious disease caused by toxigenic corynebacteria diphtheria. Transmitted by airborne droplets, it is characterized by local fibrous inflammation mainly of the mucous membranes of the mouth and nasopharynx, phenomena of general intoxication and damage to the cardiovascular, nervous and excretory systems. The damaging effect on organs and tissues is caused by the toxin secreted by the pathogen at its location.

The causative agent of diphtheria belongs to the species Corynebacterium diphtheriae of the genus Corynebacterium, family Actinomyceae.

Morphology. A distinctive feature of C. diphtheriae is polymorphism, manifested in a variety of cell shapes. In the culture of the same strain, along with the typical long curved rods, one can find short, thick ones, with swellings at the ends, giving them a club-like appearance. Dimensions vary from 1 to 6 µm in length and from 0.3 to 0.8 µm in diameter. Diphtheria bacteria are characterized by uneven staining of cells due to the presence of volutin grains in them, which perceive any aniline dye more intensely than protoplasm, as a result of which, when stained according to Leffler or Neisser, they appear in the form of granules, respectively, dark blue or blue-black. These granules are most often located in club-shaped thickenings at both ends of the corynebacteria.

The causative agents of diphtheria in smears are often located in pairs, at an acute angle to one another, which is explained by a peculiar type of cell division by fracture (“clicking type” of division), in contrast to non-pathogenic corynebacteria, which are characterized by a parallel arrangement in the smear.

They do not form spores, capsules, or flagella.

Cultural properties. The causative agent of diphtheria is an aerobe or facultative anaerobe, the optimal growth temperature is 37 0 C;

heterotroph, that is, it belongs to the group of bacteria that require for their growth organic matter. The media used for cultivation must contain amino acids as a source of carbon and nitrogen - alanine, cystine, methionine, etc. In this regard, selective cultivation media are those that contain animal protein: blood, serum, ascitic fluid. On the basis of this, the classical environment of Leffler was created, and then the environment of Clauberg and Tyndall.

Based on the cultural and biological properties of corynebacteria, diphtheria is divided into three biovars: gravis, mitis, intermedius, which differ in a number of characteristics. The most clear differentiation of types can be made by the shape of the colonies when the culture is grown on blood agar with the addition of tellurite.

Colonies of the gravis type reach 1-2 mm in diameter after 48-72 hours, have wavy edges, radial striations and a flat center (R-shape) of black or gray color. When growing in broth, gravis-type cultures form a crumbling film on the surface. On Hiss media with the addition of whey, they break down polysaccharides - starch, dextrin, glycogen with the formation of acid. Toxigenic strains of corynebacteria diphtheria belong to this biovar.

Mitis-type cultures on tellurite blood agar grow into large, slightly convex, smooth-edged, matte black colonies (S-shape). When growing in broth, they produce uniform turbidity and sediment. Starch, dextrin and glycogen are not broken down. Cultures of this type are generally less toxigenic and invasive than Corynebacterium biovar gravis.

Corynebacterium biovar intermedius occupy an intermediate position. Colonies grown on tellurite agar are small (RS-form), black in color, do not ferment starch and glycogen, and grow in broth with the appearance of turbidity and granular sediment.

Antigenic structure. Corynebacterium diphtheria is characterized by a complex antigenic structure and a variety of serological properties. The agglutination reaction reveals protein thermolabile R-antigens of a toxin-specific nature, localized in the surface layer of the cell wall, while the O-antigen is type-specific.

Among the corynebacteria of diphtheria, there are 19 phagotypes, with the help of which sources of infection are identified; they are also taken into account when identifying selected crops.

Serological properties are best studied in strains of the gravis variant. Its toxigenic strains are divided into five to nine serovars. The distribution of the latter in different territories is not the same; several serovars can circulate in the same territory, but one of them predominates.

Pathogenicity factors. Diphtheria corynebacteria produce strong exotoxins (histotoxin, dermonecrotoxin, hemolysin) in broth cultures. Toxinogenesis of diphtheria corynebacteria is determined by the gene contained in the prophage; therefore, the main means of aggression - toxin formation - is not associated with the bacterial chromosome. The peculiarity of toxin formation of the diphtheria bacillus is determined by its presence in the DNA of a specific prophage containing a structural toxicity gene, which is designated as TOX*. Thus, a diphtheria bacillus that is not infected with a specific phage is not capable of toxin formation. When it is infected by a prophage, TOX+ attaches to the DNA of the microbial cell. Due to the fact that the diphtheria bacillus is able to control the prophage, the effect of lysogeny is realized only with physiological aging or inhibition of the main life processes of the microbial cell, when the prophage gets out of control and ensures pronounced phage reproduction.

The toxic effect of diphtheria toxin is based on the ability to suppress the biosynthesis of cellular protein, which is considered as the main cause of cell death and death of the body from diphtheria infection. Diphtheria toxin is a potent bacterial toxin and is second only to botulinum and tetanus. The toxin molecule consists of two fragments, one of which is thermostable and has enzymatic activity, the second is thermolabile and performs a protective function. After adding a 0.3-0.4% formaldehyde solution to the toxin and then keeping it at 38°C for three to four weeks, it is converted into an toxoid used to prepare a prophylactic drug.

During their life, diphtheria bacteria produce, in addition to the toxin, neuraminidase, hyaluronidase, necrotizing and diffusion factors.

Resistance. Diphtheria bacteria have significant resistance to environmental factors. In diphtheria film, droplets of the environment adhering to the wall of a glass, on door handles, children's toys, they can survive.

lasts up to 15 days, in water and milk - up to 20. Survival on environmental objects in the autumn-spring period reaches 5.5 months and is not accompanied by loss or weakening of their pathogenic properties. Unfavorable factors include direct sunlight, high temperature, and chemical agents. When boiled and in alcohol, diphtheria bacteria die within 1 minute, in a 10% solution of hydrogen peroxide - after three.

Epidemiology. The source of diphtheria is a person in whom it manifests itself in different clinical forms - from severe toxic to erased forms and healthy bacteria carriers.

The epidemiological significance and role of the source of infection in the implementation of the infection mechanism is determined mainly by the intensity of transmission of the infectious agent (pathogen). Naturally, the greater the contamination of the mucous membranes of the upper respiratory tract, the more likely it is that the pathogen can be released in mass doses into the environment when talking, coughing, or sneezing. The most dangerous in this regard are patients with diphtheria and bacteria carriers. The density of colonization of mucous membranes by corynebacteria diphtheria increases sharply in people with inflammatory diseases of the upper respiratory tract, tonsillitis, and tuberculosis. The prevalence of bacterial carriage of Corynebacterium diphtheria varies from 0 to 60%, which indicates the influence of the state of the body on the carriage process.

Pathogenesis. The highest incidence of diphtheria is noted in the fall, which is explained by an increase in crowding of the population at this time of year and a decrease in the body's resistance under the influence of cooling.

Susceptibility to diphtheria infection and the development of the disease are determined by a number of factors, the main of which should be considered the immunological state of the body, age, tissue resistance at the site of introduction of the pathogen, the state of the nervous system and general reactivity.

The body's reaction to the introduction of bacteria can be local and general, the degree and nature of which depend mainly on the body's defenses. A local reaction manifests itself at the point of introduction of the microbe. Before the toxin begins to act, the pathogen must go through the stage of engraftment and reproduction on the mucous membrane of the oropharynx, nasopharynx or skin. Once on favorable soil, the pathogen multiplies, produces an exotoxin, which is fixed on cell membranes, and then penetrates deep into the tissues and affects the nerve endings embedded in the walls of blood vessels, which leads to congestive hyperemia and the formation of exudate.

At the site of entry of the diphtheria pathogen (throat, nose, trachea, conjunctiva of the eye, skin, vulva of the vagina, wound surface), films with a large number of diphtheria corynebacteria and other microbes are formed. The produced exotoxin causes necrosis and inflammation of the mucous membranes and skin. When absorbed, it affects nerve cells, heart muscle, parenchymal organs, and causes general severe intoxication. Profound changes occur in the heart muscle, blood vessels, adrenal glands, as well as in the central and peripheral nervous system.

Clinic. The incubation period for diphtheria lasts two to ten days, the disease develops acutely. According to the localization of the process, diphtheria of the pharynx, respiratory tract (diphtheria croup), and nose is most often observed. Diphtheria of the eyes, ears, genitals, and skin is relatively rare. Diphtheria of the pharynx accounts for more than 90% of all diseases, with nasal diphtheria taking second place.

The disease begins with an increase in temperature with symptoms of general malaise. A cough appears immediately - at first it is a dry, rough “barking” cough, then it loses its sonority and becomes hoarse. Diphtheria films appear on the larynx, it swells and narrows.

Then the stenotic stage develops: the breathing noise is whistling in nature, reminiscent of the sound of a saw in damp wood; it is so strong that it can be heard in the next room. Breathing is accompanied by retraction of the compliant areas of the chest and tension of the auxiliary respiratory muscles.

The third stage - asphyxial - lasts from several minutes to tens of hours and is characterized by symptoms such as severe anxiety, change in skin color. She becomes covered in sweat, her lips, face, and limbs turn blue. A paradoxical pulse appears, convulsions occur, and death occurs.

Immunity in diphtheria is antitoxic and antibacterial in nature, while antitoxic immunity plays a decisive role in anti-infective protection.

Laboratory diagnostics. Bacteriological the method is based on selection pure culture and identification of pathogens by cultural, morphological, biochemical and toxic properties. The object for research is the discharge of the pharynx, nose, eyes, skin, etc., which is taken with a cotton swab and sown on Clauberg's medium or blood tellurite agar. The listed media contain 0.04% potassium tellurite, which suppresses the growth of accompanying microflora (staphylococci, streptococci). After 24-48 hours of cultivation, microscopy of smears is performed and a preliminary answer is given.

Diphtheria corynebacteria are not always morphologically typical; in some cases the pathogen takes the form of short rods, located not at an angle, but randomly, with weak granularity. In addition, the formation of volutin granules does not always occur and, therefore, this sign is not absolute. The most reliable method is toxin formation. Differentiation of toxigenic and non-toxigenic strains is carried out using the Ouchterlony method (double immunodiffusion method in Petri dishes or precipitation method in agar). It is based on the ability of diphtheria exotoxin to combine with antitoxin and form precipitates in the form of arrows - antennae.

Serological reactions are used to study herd immunity. They include: RPGA, characterized by high sensitivity, carried out with an antibody diagnosticum;

Schick test, carried out to determine individual immunity to diphtheria toxin; reaction to neutralize the cytotoxic effect of diphtheria toxin in tissue culture; RIA; enzyme immunoassay (ELISA).

Treatment. The main thing in the treatment of all forms of diphtheria is the neutralization of diphtheria toxin with the antitoxic anti-diphtheria serum "Diaferm". For moderate severity of the disease, 5000-15,000 IU is administered, for severe forms - 30,000-50,000 IU. Antibiotics are prescribed to treat carriers.

Prevention includes early diagnosis, immediate hospitalization, complete disinfection of the premises and objects, identification of carriers.

Specific prevention against diphtheria consists of active immunization of children from the age of five months using the method of primary double vaccination and distant single revaccination with pertussis-diphtheria-tetanus vaccine (DPT).

Related information.