Diphtheria

causative agent of diphtheria

Diphtheria — an acute infectious disease, life-threatening. It occurs as an acute inflammation of the upper respiratory tract, pharynx predominantly (about 90%), the nose, the skin at the point of damage to the eye or genitals.

The main threat, however, is not the inflammation and poisoning toxin that the bacterium — the causative agent of the disease, with mainly affects the cardiovascular and nervous systems.

Pathogen and route of infection

The causative agent of diphtheria are Corynebacterium diphteriae — Gram-positive bacteria in the form of rods with characteristic cone-shaped thickenings at the ends, which smears are pairwise at an angle of a Roman numeral V relative to each other. Diphtheria bacilli in the process of life is isolated diphtheria toxin, enzyme neuraminidase and other biochemically active compound.

Synthesis of diphtheria toxin microbial cells is controlled by a special gene tox. Bacteria can lose his life in the process, losing with it, and its ability to produce a toxin (toxigenicity). Conversely, originally nontoxigenic strains can acquire pathogenic properties, fortunately, this happens very rarely.

The disease is transmitted by airborne droplets from diphtheria patients or healthy carriers of infection, much less — through household items.

Most susceptible to infection with diphtheria in children aged 3-7 years, but in recent years has increased the incidence of adolescents and adults.
The source of the infection are sick people or healthy carriers of toxigenic bacteria. Most infectious suffering diphtheria throat, nose and throat, as they actively infective isolated from the exhaled air. Patients with diphtheria eyes, skin infection can spread by contact (hands, household items). Healthy carriers of bacteria is much less contagious, but the lack of any outward signs of their condition does not allow them to control the spread of infection, because they can be identified only by accident in the course of mass medical examinations. As a result, the majority of cases of diphtheria caused by contact with healthy carriers of diphtheria bacilli.

The incubation period (time from infection to the first signs of the disease) is 2-10 days.

Diphtherian toxin

The toxin produced by diphtheria wand consists of several components. One — hyaluronidase enzyme destroys hyaluronic acid capillaries and increase their permeability, which leads to failure of blood vessels and surrounding tissues impregnated with deposition of blood plasma protein fibrinogen. The second component — nekrotoksin destroys the cells of the epithelium with the release of these enzymes trombokinazy. Trombokinaza promotes the conversion of fibrinogen into fibrin and formation of tissue on the surface of fibrin film. Under the action of diphtheria toxin on the tonsils, which are coated with several layers of epithelial cells formed fibirinnaya film that penetrates deep into the epithelium of the tonsils and tightly welded to it.

The third (main) components — the actual toxin is able to block the process of cellular respiration and the synthesis of protein molecules. The most sensitive to its effects are capillaries, myocardial cells and nerve cells. As a result of developing myocardial degeneration and infectious-toxic myocarditis, capillary damage leads to infectious-toxic shock, damage to the Schwann cells (helper cells in the nervous tissue) leading to demyelination of nerve fibers (an insulating layer of myelin destruction in violation of nerve impulses along nerve fibers). Furthermore, diphtheria toxin intoxication is common organism.

Symptoms and course

Diphtheria throat usually begins with a low-grade fever, slight pain on swallowing, redness and swelling of the tonsils, forming them specific membranous deposit, increasing the front upper cervical lymph nodes. Colour films — usually white in the first 2-3 days of illness, but then becomes gray or yellowish-gray color. Approximately a week later disease or recovery end (mild, usually in vaccinated against diphtheria) or becomes more severe toxic form associated systemic action of diphtheria toxin.

The toxic form of diphtheria always takes very seriously. It is characterized by extremely high body temperature (39,5-41,0 ° C), severe headaches, drowsiness, apathy. The skin becomes pale, dry mouth observed in children can be repeated vomiting and abdominal pain. Swelling of the tonsils become pronounced, can lead to complete closure of the entrance to the throat, extending to soft and hard palate, often as the nasopharynx, difficult breathing, nasal voice often becomes. Plaque is distributed to all tissues oropharynx. The classic sign of a toxic form of diphtheria throat is swelling of the subcutaneous tissue in the neck, and sometimes the chest, causing the skin takes on a gelatinous consistency. Front upper cervical lymph nodes are significantly enlarged and painful.

Diphtheria of the nose proceeds with normal or slightly elevated body temperature, no intoxication. From the nasal passages can be seen seropurulent or saniopurulent discharge. On the wings of the nose, cheeks, forehead and chin areas appear soak and then dry crust. Inside the nose visible filmy raids. Disease process may also affect the paranasal sinuses. If there is a toxic form of swelling of subcutaneous tissue of cheeks and neck.

Diphtheria eyes proceeds as banal conjunctivitis is characterized by moderate conjunctival hyperemia and edema of the century, a small amount of sero-purulent discharge from the conjunctival sac (catarrhal form). Filmy form shows a pronounced swelling of the eyelids, conjunctiva having their films more difficult to remove grayish-white in color. The toxic form is also accompanied by swelling of the tissue around the eye socket.

Diphtheria skin privoditk long not healing any damage to the skin, redness on the skin there is a dirty-gray patina, there is a dense infiltration of the surrounding skin.

Diagnostics

Diagnosis of diphtheria is carried out on the basis of the examination of the patient and the test results. On examination for diagnosis diphtheria say the following features: the presence of specific films, as well as difficulty breathing and a whistling noise on inspiration, not typical for angina, barking cough. The diagnosis of diphtheria in the characteristic clinical signs in disease are mild, put more complicated.

Analyses:

1. Complete blood count — the signs of acute inflammation.

2. Smear under a microscope (bacterioscopy) — identification with a distinctive type of bacteria Corynebacterium diphteriae.

3. Bacteriological examination — sowing the biological material to a special growth medium and cultivation of colonies of microorganisms.

4. Determining the level (titer) of antitoxic antibodies (titer higher — 0.05 IU / ml or higher eliminates diphtheria).

5. Serology — Determination of specific antibodies in the serum using methods HAI, ELISA, etc.

Diphtheria throat must be differentiated from acute tonsillitis (follicular and lacunar forms), angina Simanovskiy-Vincent (fungal infection), syphilitic sore throats, tonsillitis lozhnoplenochnoy in infectious mononucleosis, paratonsillar abscess, mumps, leukemia. The children need to take a false diagnosis of croup.

Treatment

Of all cases of diphtheria, regardless of the severity of the condition, you need to be hospitalized in the infectious diseases hospital.

Treatment consists of the following:

1. Diet — Fortified, calorie, held a thorough cooking of food.

2. Causal treatment (that is aimed at addressing the causes of disease) — the introduction of diphtheria serum (PDS), the dose and the amount of time of administration depends on the severity and form of the disease. In mild VCP injected intramuscularly at a dose of 20-40 IU thousand at moderate form — 50-80 thousand IU singly or, if necessary, again with the same dose 24 hours later. In the treatment of severe forms of the disease the total dose is increased to 90-120 thousand IU or even up to 150 thousand IU (toxic shock, DIC). When 2/3 of the dose administered once, and during the first day of hospitalization to be administered 3/4 of the total dose.

3. Antibiotics: the milder forms — erythromycin, rifampin inside, with moderate to severe forms — injection of penicillin or cephalosporins. The duration of the course — 10-14 days. Antibiotics have no effect on the diphtheria toxin, but reduce the amount of bacteria producing it.

4. Local treatment — rinse and irrigation disinfectants.

5. Detoxification therapy — glucose-saline solutions, taking into account the daily fluid requirements and its loss (moderate and severe).

6. Corticosteroids — with moderate and severe forms.

Treatment with antibiotics bacteria carriers hold: tetracyclines (children older than 9 years), erythromycin, cephalosporins against strengthening therapy and elimination of chronic foci of infection.

Complications

Among the most serious oslozhneniydifterii on the cardiovascular system can be isolated myocarditis, cardiac rhythm.

Neurological complications of diphtheria are caused by lesions of various cranial and peripheral nerves and appear paralysis of accommodation, strabismus, limb paresis, and in more severe cases, paralysis of respiratory muscles and muscles of the diaphragm.

Secondary complications of diphtheria are serious pathological conditions such as acute ischemic attacks (thrombosis, embolism), metabolic encephalopathy, cerebral edema, renal toxicity, diphtheria hepatitis, as well as toxic shock and disseminated intravascular coagulation syndrome (dessiminirovannogo intravascular coagulation — a serious disturbance of blood clotting). The toxic form of diphtheria can lead to acute renal, cardiovascular, respiratory or poliorgannnoy failure.

Non-specific complications of diphtheria are paratonsillar abscess, otitis media, pneumonia.

Vaccination

Vaccination against diphtheria toxoid is held, that is inactivated toxin. In response to its introduction into the body is not produced antibodies to Corynebacterium diphteriae, and to diphtheria toxoid.

Diphtheria toxoid part of the combined domestic DTP (associate, that is integrated, the vaccine against diphtheria, pertussis and tetanus), AaKDS (vaccine with acellular pertussis) and DT (diphtheria-tetanus toxoid), and "forgiving" Td vaccine and BP-M. In addition, the Russian company registered vaccine «SanofiPasteur»: Tetrakok (diphtheria, tetanus, pertussis, polio), and tetrakis (diphtheria, tetanus, pertussis, polio, with acellular pertussis), DT Wachs (diphtheria-tetanus toxoid vaccination for children up to 6 years) and DT Imovaks Adyult (diphtheria-tetanus toxoid vaccination for children older than 6 years and adults), as well as Pentaxim (vaccine against diphtheria, tetanus, pertussis, polio and Haemophilus influenzae with acellular pertussis).

According to the Russian immunization schedule, vaccination of children under the age of 3 is held in, 4-5, and 6 months. The first revaccination is carried out in 18 months, the second — in 7 years, and the third — in 14. Adults need to re-vaccinated against tetanus and diphtheria every 10 years.

 

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