Clinical manifestations and indications for hospitalization
The clinical picture of the disease consists of two main syndromes. Signs of infection generalization include pronounced intoxication and an enlarged liver (hepatomegaly). Concurrently, signs of sensitization of the body to pathogen antigens develop, which clinically manifests as joint pain (arthralgia) and skin rash (exanthema).
If a moderate-to-severe course of the generalized form is suspected in a patient, this is a direct indication for hospitalization. Treatment of such patients should be carried out in a specialized infectious diseases hospital.
Erythema nodosum: a marker of sensitization
One of the prominent manifestations of the reactive phase of the disease is erythema nodosum (erythema nodosum). Pathogenetically, it represents a manifestation of allergic arteritis localized in the subcutaneous adipose tissue.
Clinically, the rash elements appear as large, palpation-tender, and deeply situated nodules. A characteristic feature is that the elements "fade" like a regular bruise, changing color over time.
Erythema nodosum is not a strictly specific symptom, so it requires a thorough differential diagnosis. The list of likely causes, besides yersiniosis, includes:
- Tuberculosis;
- Streptococcal infection;
- Sarcoidosis;
- Paraneoplastic processes.
Anamnestic markers help suspect that the rash is specifically linked to sensitization to Yersinia antigens. These include a recently suffered intestinal infection or surgery for acute appendicitis (e.g., about a month ago).
Laboratory diagnostics
If the disease lasts for more than a week, a set of laboratory methods aimed at detecting specific antigens and antibodies is used to verify the diagnosis. Antibodies can circulate in the blood either freely or as part of ICCs (immune complexes).
Blood serum testing:
- The IHA method (indirect hemagglutination assay) is used to search for specific antibodies.
- The ELISA method (enzyme-linked immunosorbent assay) is used to detect Yersinia antigens.
Saliva and coprofiltrate testing:
- The co-agglutination test is used to search for pathogen antigens in these biological fluids.
Principles of pseudotuberculosis therapy
Treatment is based on a combination of antibacterial and pathogenetic management.
Before final laboratory results are obtained, empiric antibiotic therapy is prescribed. The drugs of choice at this stage are fluoroquinolones and semi-synthetic tetracyclines.
Pathogenetic therapy is necessary if there are signs of sensitization and reactive inflammation (e.g., with pronounced arthralgia). In such cases, the prescription of the following is indicated:
- Antihistamines;
- NSAIDs (nonsteroidal anti-inflammatory drugs).
Special tactics in the reactive phase: If the reactive phase develops after a prior appendectomy (performed for suspected yersiniosis-induced appendicitis), the tactics change. If the patient has already received an adequate course of antibiotic therapy post-surgery, re-administration of antibiotics is not required. The main focus is on suppressing inflammation: the patient is prescribed NSAIDs, antihistamines, and vitamin therapy (ascorbic acid).
Briefly: answers to topical questions
Which specific microorganism is the causative agent of pseudotuberculosis?
The causative agent of pseudotuberculosis is the Gram-negative facultatively anaerobic bacterium Yersinia pseudotuberculosis. It belongs to enteropathogenic Yersinia, whose natural habitat is the environment (soil, water). Characteristic properties of the microorganism are psychrophilia (the ability to multiply at low temperatures, optimum 22–25 °C) and oligotrophy (the ability to survive at low nutrient levels). Epidemic outbreaks of generalized pseudotuberculosis, historically referred to as "Far Eastern scarlatiniform fever", are caused by Yersinia pseudotuberculosis type 1.
What are the main mechanisms and routes of transmission of pseudotuberculosis?
The primary mechanism of transmission of pseudotuberculosis is fecal-oral. The following routes of infection are distinguished:
- Foodborne route — is the leading one. Infection occurs through raw or poorly heat-treated products from refrigerators. In pseudotuberculosis, the main significance lies in vegetables (cabbage, carrots, onions) stored in vegetable storage facilities.
- Waterborne route — is less common.
- Contact-household route — is also less common.
The main source and reservoir of infection are synanthropic rodents, as well as soil, from which bacteria penetrate into vegetables through the root system.
To remember the basis of therapy in the reactive phase (after appendectomy), use the acronym NAV: NSAIDs, Antihistamines, Vitamin C (ascorbic acid).
Class and exam questions
In what cases is hospitalization mandatory for pseudotuberculosis?
The patient is subject to hospitalization in an infectious diseases hospital if a moderate-to-severe course of the generalized form of the disease is suspected.
What diseases are included in the differential diagnosis of erythema nodosum?
Differential diagnosis includes yersiniosis, tuberculosis, streptococcal infection, sarcoidosis, and various paraneoplastic processes.
What methods are used for blood serum testing when the disease duration exceeds a week?
The IHA method is used to detect specific antibodies, and ELISA is used to search for Yersinia antigens.
Is it necessary to re-prescribe antibiotics if a reactive phase develops after an appendectomy?
If adequate antibiotic therapy has already been administered after appendectomy surgery, re-administration of antibiotics is not required; pathogenetic treatment is indicated.
What else to study on this topic
- Pathogenesis of circulating immune complex (CIC) formation
- Mechanisms of development of allergic arteritis in infectious diseases
- Specificity of the co-agglutination test in coprofiltrate analysis
- Features of fluoroquinolone use in empiric therapy of intestinal infections
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