Diagnosis of gastrointestinal and pulmonary forms
The clinical picture of generalized forms does not have prominent specific features distinguishing it from other severe infections accompanied by intoxication and hemorrhagic syndrome.
Therefore, the epidemiological history plays a key role:
- History of contact with infected meat and dairy products.
- Suspicion of biological weapon use (bacterial aerosol).
The definitive diagnosis is established based on laboratory and instrumental findings.
Laboratory tests
Biomaterial is collected prior to initiation of treatment, as antibiotics and sera hinder the isolation of the pathogen. For the pulmonary form, blood and sputum are examined; for the intestinal form, feces, urine, and blood. In fatal cases, autopsy material (liver, spleen, lymph nodes) is collected.
Methods for detecting B. anthracis:
- Microscopy: Gram-stained smears reveal large Gram-positive rods, frequently in chains. To visualize capsules, Loeffler's methylene blue, Giemsa stain, or Rebiger's solution is used.
- Bacteriological culture: material is inoculated onto meat-peptone agar (MPA) and broth (MPB). In the pulmonary form, blood culture is the most valuable test (growth in 6–24 hours, final report in 24–48 hours).
- Biological assay: inoculation of laboratory animals to confirm that the culture belongs to the anthrax agent.
Immunodiagnostics and allergodiagnostics
A number of specific methods are used for rapid diagnosis and confirmation:
- Fluorescent antibody test (FAT): detects fluorescence of bacilli treated with labeled antiserum. Yields a preliminary result on day 1.
- Ascoli test (thermoprecipitation): interaction of the antigen extract with precipitating serum (preliminary diagnosis).
- PCR: detection of pathogen DNA.
- ELISA and IHA: serological detection of antibodies and antigens.
Allergodiagnostics is performed using anthraxin. The reaction is considered positive if after 48 hours the infiltrate and hyperemia reach 10 mm or more. The method is highly informative during the first week of illness (85–90%). Important: the test is not evaluated if the patient was vaccinated against anthrax within the past year.
Instrumental findings in the pulmonary form
In pulmonary involvement, chest radiography and CT scan reveal characteristic changes that develop in the late stages of the disease:
- Marked widening of the mediastinal shadow (edema, mediastinitis).
- Changes in mediastinal lymph nodes.
- Peribronchial thickening.
- Presence of pleural effusion.
Differential diagnosis
Pulmonary anthrax must be differentiated from other severe respiratory infections:
- Pneumonic plague.
- Pneumonic tularemia.
- Pneumonias and bronchopneumonias of other etiology.
Briefly: answers to topical questions
Which antibacterial drugs are the drugs of choice for treating the generalized form of anthrax?
In the cited sources, benzylpenicillin is indicated as the drug of choice for infections caused by Bacillus anthracis (anthrax). Specific regimens, combinations, dosages, or course durations specifically for the generalized form of anthrax are not provided in the sources; it is only stated that etiotropic therapy must be selected strictly according to clinical forms and disease variants.
What specific pathomorphological changes develop in the intestinal wall and mesenteric lymph nodes in the intestinal form?
In intestinal anthrax, extensive areas of hemorrhagic infiltration and superficial ulcers are described in the intestine; focal (carbuncular), diffuse (edematous), and mixed forms of lesions are distinguished. Mesenteric lymph nodes, mesentery tissue, and retroperitoneal fat are markedly edematous, black-red, and infiltrated with serosanguineous exudate. Microscopic findings include serosanguineous enteritis and hemorrhagic lymphadenitis. Serosanguineous effusion and peritonitis may be present in the abdominal cavity; involvement of the intestinal wall can lead to perforation and peritonitis.
How is Ascoli's thermoprecipitation test technically performed and evaluated?
Technically, Ascoli's thermoprecipitation test is performed in narrow precipitation tubes using layering methods.
A cell-free anthrax antigen—aqueous extracts of organs, tissues, or scab that have been pre-boiled and filtered—is used as the antigen. This antigen solution is carefully layered onto a specific precipitating (immune) serum, creating an interface and avoiding mixing of the liquids.
Evaluation of results is performed visually: in a positive reaction, a characteristic opaque precipitate ring forms at the boundary of the two liquids (at the interphase). The formation of this ring occurs due to diffusion and the achievement of an optimal ratio of reactants at the media boundary.
Class and exam questions
Antibiotics and specific immune serum suppress the viability of the pathogen, making its isolation extremely difficult or impossible.
Antibiotics and specific immune serum suppress the viability of the pathogen, making its isolation extremely difficult or impossible.
If the patient was vaccinated against anthrax in the preceding 12 months, a positive skin allergy test result is disregarded, as it may be the result of vaccination.
If the patient was vaccinated against anthrax in the preceding 12 months, a positive skin allergy test result is disregarded, as it may be the result of vaccination.
To visualize capsules, Rebiger's solution, Loeffler's methylene blue, or Giemsa stain is used. With Rebiger's stain, capsules turn red-violet, while bacteria appear dark violet.
To visualize capsules, Rebiger's solution, Loeffler's methylene blue, or Giemsa stain is used. With Rebiger's stain, capsules turn red-violet, while bacteria appear dark violet.
What else to study on this topic
- Clinical picture of cutaneous anthrax
- Differential diagnosis of cutaneous form with carbuncles and erysipelas
- Differential diagnosis of cutaneous form with plague and tularemia
- Mechanisms of action of anthrax toxin
- Anti-epidemic measures in the infection focus
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