Lecture of anthrax (Anthrax)

2021-01-31 12:00 AM

In blood agar medium, B. anthracis is grey-white, colony rough, insoluble or weakly hemolytic. In contrast, in an environment rich in CO2 (sodium bicarbonate), the colonies are smooth.

Define

Anthrax is an acute, zoonotic, bacterial infection caused by the bacillus anthracis.

The clinical manifestation in humans is a severe systemic infection-intoxication syndrome, the most common lesions are the skin. Respiratory and gastrointestinal form is uncommon but very severe with high mortality.

Anthrax is one of the diseases classified as "particularly dangerous". Coal bacteria are easy to study and use in biological warfare.

Research history

The first descriptions of anthrax are known from 1491 BC, causing illness in both animals and humans. By the 17th century, the disease had killed many people and animals across Europe.

In 1881, Pasteur developed a vaccine and in 1939 Sterne successfully created a vaccine for anthrax.

Epidemiology

High-risk areas are South and Central African countries, South and Eastern Europe, Asia, Africa, the Caribbean and the Middle East.

Pathogens

Anthrax bacilli (Bacillus anthracis), gram (+), belonging to Bacillaceae, bacilli are large (3-10 x 1-1.5 mm), jacketed, not mobile. The charcoal bacilli usually stand together in chains, sharing a shell, like a "bamboo-segment".

In soil, the bacillus forms oval-shaped spores, which are smaller in size and can last for decades in harsh natural conditions. But the spores are easily killed when boiled for 10 minutes or oxygen-rich substances (potassium permanganate, H2O2 ...).

In blood agar medium, B. anthracis is grey-white, colony rough, insoluble or weakly hemolytic. In contrast, in an environment rich in CO2 (sodium bicarbonate), the colonies are smooth.

The toxin of B. anthracis is called anthrax toxin (anthrax-toxin), which consists of 3 proteins linked together. The shell (polypeptide) has an anti-phagocytic effect.

Inoculum

Being domestic animals, mainly herbivores: Buffaloes, cows, horses, donkeys, sheep, goats, camels, deer ... are sick. When dead, these animals spread pathogens into their surroundings. The spores can exist for a long time, many years in the soil, animal skin is old, animal hair, canned meat, smoke ...

Other animals such as pigs, mice ... can also be the source of the disease.

Infection

The main route of transmission is the skin-mucosal route (skin and mucous membranes), due to contact with pathogens from infected, dead animals or products from these animals (skin, fur, etc.). or spores in soil (indirect infection).

Secondary: inhaled by inhalation of dust with coal spores (found in the tanning workshop, processing animal hair ...). In biological warfare, the enemy often applies the respiratory tract (aerosol-type coal spore spray).

Gastrointestinal tract: by eating contaminated meat.

There are documents dealing with blood-borne transmission through blood-sucking insects (buffalo flies, yellow flies ...).

Sense of the body

People of all ages are equally likely to get sick.

After the disease, has relatively stable immunity (almost does not get it again)

Subjects susceptible to the disease are farmers, veterinarians, slaughterhouse workers, buffaloes, cows, sheep ... tannery, animal hair ...

The disease occurs all year round, but the epidemic is common in the summer. The cases of infection caused by infection from articles made of leather, animal hair ... can be scattered.

Mechanism of pathogenesis and pathology

Mechanism of pathogenesis

  1. anthracis after entering the body (through the skin, mucous membranes), thanks to virulence factors (polypeptide shell and anthrax toxin) exits phagocytes. Anthrax toxins include 3 proteins: protective antigen, oedema factor and lethal factor. Then, they colonize, multiply and damage (oedema, necrosis ...) regional lymph nodes.

The bacteria escape the body's support, from the lymph nodes along the lymphatic pathways and blood to the body's organs and cause disease. Depending on the organ damaged, there are different diseases.

Pathological anatomical injury 

Common pathological anatomical characteristics of organs are congestion causing blood stasis, haemorrhage and necrosis.

Skin: The specific skin lesions in anthrax are ulcers caused by necrosis, congestion, haemorrhage, and oedema.

Lungs: Very strong pulmonary congestion; haemorrhage and necrosis of mediastinal lymph nodes; Pneumonia can be encountered.

Gastrointestinal: Hemorrhage and necrosis of intestinal and mesenteric lymph nodes. It is also possible to damage the oropharyngeal lymph nodes (when pathogens enter through the oral mucosa).

Enlarged liver, spleen, kidney (due to congestion), bleeding ...

Cerebrospinal fluid is cloudy, contains many bacteria ...

Divide the clinical form

Anthrax (mainly, about 95%).

Respiratory form: rarely encountered (about 5%).

Digestive form: rare.

Meningitis: (manifested as meningitis): very rare and only secondary due to complications of septicemia of other types, so it is of little importance.

Symptoms study according to the clinical form

Infection: from a few hours to a few days (3-9 days), but most of the time within 48 hours after exposure.

Skin anthrax

Anthrax: An ulcer, where the pathogen penetrates the skin (usually in the open skin: legs, arms, neck, face ...), progresses through the following stages: maculopapular, nodule, posterior purple red blisters (blood blisters). Severe itching, the patient scratching, rupture, extensive necrosis, after 2-4 days forming a large ulcer, on the surface covered with a hard black scab. Around the ulcer there are many small secondary blisters ("pearl ring" image). At the ulcer, the patient feels no pain, even when the needle is inserted. After 3-4 weeks, the ulcer scabs, forming a white scar.

The swelling around the ulcer is very strong and widespread. Compressed edema (swelling of the neck, chest causing compression to the trachea ...) and signs of "frozen meat" (Stephan ski sign).

Lymph nodes in the area of ​​the ulcer are often swollen, but painless, without pus.

Severe systemic infection-poisoning syndrome: High fever of 39-400C, chills, fatigue, headache, insomnia ... Peripheral blood leukocytes increased very high ( 20 000 / mm3).

If left untreated, anthrax is 5-20% fatal; If treated, death rarely occurs.

Respiratory form

Severe infectious-intoxication syndrome (as if skin).

Chest pain, shortness of breath, manifestations of pneumonia or bronchitis, coughing up rust-coloured sputum; pleural effusion or pulmonary oedema sometimes occurs.

Lung X-ray: Mediastinum dilated due to inflammation of the mediastinal lymph nodes. Lung parenchyma with diffuse dense infiltration ...

Severe: Breathlessness, cyanosis, shock ...

Digestive

Severe infection-intoxication syndrome.

Abdominal pain, vomiting, blood and mucus stools ... The disease is like hemorrhagic necrotizing enterocolitis; sometimes resembles a surgical abdominal emergency (due to mesenteric lymphadenitis ...)

Implementing the quadrants

Based on clinical (mainly cutaneous) and epidemiology, but the decisive significance for the diagnosis is specific testing:

Staining: (this technique is only of directional value). Specimens are blood fluid in pustules, sputum, urine, faeces, vomit, organ fluid ... Gram stain for bacteria: gram (+). Staining Ziehl - Neelson: detection of spores.

Culture for bacteria.

Rapid diagnosis by immunofluorescence method.

Skin reaction with anthraxcin antigens: Intradermal injection of 0.1 ml of antigen extracted from the outer membrane of bacteria (anthraxcin). If there is immunity to anthrax, at the injection site, the red halo is> 3cm in diameter.

Differential diagnosis

The skin form of anthrax with the plague: Although there are manifestations of severe infection-intoxication, swollen lymph nodes; but in the plague, the lymph nodes are swollen and very painful, pus and rupture ...

Ulcers of anthrax with ulcers in tularemia or staphylococcal ulcers: different from anthrax, ulcers in tularemia and staphylococcus are not scaly, little oedema and just around ulcers, less pain ...

Tuberculosis ulcers: the same is the same black scaly, but smaller, no oedema around, no secondary bulging, leukocytes usually do not increase ...

Treatment

Need treatment as soon as possible. Isolation of patients in a private room, service staff must have gloves and boots.

Antibiotic

Penicillin G 4,000,000UI intravenously every 4-6 hours x 7-10 days.

Or: Ciprofloxacin 400mg every 8-12 hours. Tetracycline 0.4 g / time (or Doxycycline 100 mg) x4 times / day for 7-10 days.

Other alternative antibiotics: erythromycin, amoxicillin, chloramphenicol ...

For the respiratory and digestive forms: higher doses should be used and resuscitation must be combined.

Cardiovascular aids, water and electrolyte replenishment.

Do not cut the pimples because they easily cause sepsis.

If there is specific Gamma globulin or antitoxin serum, then use it well.

Standard of discharge

Clinical recovery: Fever, eating, sleeping, normal activities, normal peripheral blood leukocytes ... For the skin: exfoliated, scaly pimples.

Bacterial tests were negative twice for sputum, stool, and blood, 5 days apart.

Prevention

General prevention

Ensure proper animal quarantine regime. Sick animals should not be slaughtered. Animals that die from anthrax must be buried deeply, disinfected and disinfected according to regulations ...

Workers in slaughterhouses, animal products processing factories (meat, bones, skin, feathers ...) need to comply with protection regulations, periodically check health, and skin lesions. need good treatment ...

Disinfection and disinfection of human and animal wastes.

Specific

Prevention of diseases for humans and animals at high risk with BioThraxT vaccine.

Treatment of exposure prophylaxis with ciprofloxacin (500mg orally twice daily) or doxycycline (100mg x 2 times/day). Duration of treatment after exposure is more than 6 weeks.