Salmonellosis and co-infections: pathomorphology

General features of chronic infections

A number of specific infectious processes are characterized by a potential lifelong latent course. The clinical presentation directly depends on the state of the immune system and the patient's general body resistance.

Abortive form: develops with a mild decrease in the body's resistance. It manifests as localized granulomatous rashes prone to spontaneous resolution.
Incubation period: is characterized by extreme duration, averaging 4–6 years, but in some cases can be delayed for 10–15 years or more.
Prodromal period: as a rule, proceeds asymptomatically, without pronounced phenomena.

Leprosy: classification and morphology

Leprosy is characterized by the formation of specific granulomas (lepromas) in organs and tissues. There are three main forms: tuberculoid, lepromatous, and borderline (dimorphous).

Tuberculoid form runs a relatively benign course and affects individuals with preserved immunity (often carriers of HLA-DR2 or HLA-DR3).

Depigmented spots with loss of sensitivity appear on the skin.
Peripheral nerves (facial, ulnar) are affected early, which can lead to lagophthalmos, keratitis, and foot ulcers.
Microscopically, non-caseating granulomas composed of epithelioid cells, giant cells, and lymphocytes are detected. Caseous necrosis with the formation of a nerve abscess is possible in nerve trunks.

Lepromatous form is a severe generalized variant.

The skin, mucous membranes, eyes, internal organs (testes, adrenal glands, spleen), and nerves are affected.
Brown infiltrates form on the face, eyebrows fall out, forming the so-called "lion face" (facies leonina).
A specific marker is Virchow lepra cells (multinucleated macrophages with foamy cytoplasm containing the pathogen in the form of "cigar bundles").
Without treatment, the process leads to necrosis of nodes and mutilation (auto-amputation) of the phalanges.

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Trachoma and eye lesions

Trachoma is a chronic follicular keratoconjunctivitis of a purulent nature. The disease is caused by Chlamydia trachomatis and often leads to vision loss in arid regions.

Infection: the pathogen is introduced onto the conjunctiva by contact.
Reaction: purulent inflammation occurs with the formation of lymphocytic infiltrates (follicles) in deep tissues.
Pannus: inflammation spreads to the cornea, causing its opacification and vascularization.
Outcome: scarring of eye tissues, inability to fully close the eyelids, and the development of irreversible blindness.

Parasitic infestations: schistosomiasis and filariasis

Schistosomiasis is a severe helminthiasis in which cercariae from fresh water penetrate through the skin into the venous systems of the pelvis and portal tract.

Females lay eggs, around which granulomatous inflammation forms.
Mild form: small calcifying granulomas in the intestine and liver.
Severe form: hepatotoxic egg excretions cause an accumulation of macrophages and fibroblasts, leading to massive portal fibrosis and liver cirrhosis (complications include ascites, esophageal varices).
When eggs enter the lungs, granulomatous arteritis and cor pulmonale develop. Involvement of the urinary bladder causes productive inflammation, hematuria, and is considered a precancerous condition.

Filariasis is transmitted by mosquitoes. Adult nematodes localize in the lymphatic vessels, causing their sclerosis, blockade of lymph outflow, and severe lymphedema up to elephantiasis. Eosinophilia is possible in the lungs due to the mast cell reaction to IgE.

Particularly dangerous infections

This group includes highly contagious diseases with an extremely severe course and a tendency to epidemics. They include:

Anthroponoses: relapsing fever and epidemic typhus.
Anthropozoonoses: tularemia, brucellosis, anthrax.
Quarantine infections: plague, smallpox, cholera, yellow fever.

Anthrax is an acute bacterial anthropozoonosis. Infection is often occupational (slaughterhouse and agricultural workers). Endemic to Asia, South America, and Africa.

Briefly: answers to topical questions

What are the clinical and morphological forms of leprosy, and what are their features?

There are three main clinical and morphological forms of leprosy: tuberculoid, lepromatous, and borderline.

Tuberculoid form is characterized by a relatively benign course in individuals with good immunity. It is characterized by weakly pigmented spots with clear edges and reduced sensitivity, early involvement of peripheral nerves, trophic ulcers, muscle atrophy, contractures, and possible bone resorption. Epithelioid cell granulomas are formed; mycobacteria are detected rarely or in smaller numbers than in the lepromatous form. In nerve trunks, tuberculoid granulomas are usually large and often undergo caseous necrosis with the development of a nerve abscess.
Lepromatous form is a severe generalized variant with a significant decrease in the body's resistance. The skin, mucous membranes of the nose and oropharynx, anterior chamber of the eye, peripheral nerves, reticuloendothelial system, adrenal glands, and testes are affected. Skin lesions are represented by continuous reddish-brown infiltrates, predominantly on the face and distal extremities; loss of eyebrows and eyelashes and the formation of a "lion face" (facies leonina) are possible. Foamy Virchow lepra cells with mycobacteria are present in the granulomas.
Borderline (dimorphous) form occupies an intermediate position, developing in individuals with unstable immunity. It is characterized by granulomas in the skin and mucous membranes consisting of epithelioid and giant cells surrounded by a lymphocytic rim, as well as peripheral nerve damage. Transformation into the lepromatous or tuberculoid type is possible.

What are the clinical and morphological forms of salmonellosis?

There are four main clinical and morphological forms of salmonellosis.

Gastrointestinal form (toxic) proceeds with the development of acute gastroenteritis, including gastritic, gastroenteritic, and gastroenterocolitic variants.
Generalized form (septic) develops against the background of immunodeficiency by the type of septicopyemia with the formation of an intestinal septic focus and metastatic abscesses. Includes typhoid-like and septicopyemic variants.
Typhoid-like form is characterized by changes similar to the typhoid-paratyphoid group, but less pronounced.
Bacteriogenic carrier state (subclinical form) is subdivided into acute, chronic, and transient excretion of the pathogen without clinical manifestations.

What is the morphological characteristic of skin lesions in anthrax?

In the cutaneous form of anthrax, an anthrax carbuncle is formed or acute diffuse serous-hemorrhagic inflammation occurs. Macroscopically, the carbuncle is a pitch-black scab with a hard crust, surrounded by a purplish infiltrate and extensive tissue edema containing numerous pathogens. Microscopically, an exudate poor in cellular elements is observed, while necrosis extends into the thickness of the dermis and subcutaneous adipose tissue. Regional serous-hemorrhagic lymphangitis and lymphadenitis join the primary affect. After 2–4 weeks, the scab is rejected with the formation of an ulcer, in the place of which a dense white scar subsequently forms.

What local changes in the gastrointestinal tract are characteristic of the intestinal form of salmonellosis?

For intestinal lesions in salmonellosis, catarrhal or catarrhal-ulcerative gastroenteritis, gastroenterocolitis, and terminal ileitis are described. The intestinal wall is infiltrated with neutrophils, lymphocytes, a small number of eosinophils, and plasma cells. Hyperplasia and ulceration of Peyer's patches are observed in the lymphoid apparatus of the intestine. Mesenteric lymphadenitis develops in the mesenteric lymph nodes: initially, the nodes are enlarged and hyperemic, with proliferation of monocytes and reticular cells; subsequently, specific granulomas may form, followed by necrosis of the granulomas, their organization, and petrification.

Class and exam questions

What is the main difference between the tuberculoid granuloma in leprosy and true tuberculosis?

Dermal leprotic granulomas typically lack characteristic caseous necrosis, although it may occur in affected nerve trunks.

What are Virchow cells?

These are large foamy macrophages found in the lepromatous form of leprosy, whose cytoplasm is densely packed with mycobacteria.

Why is urinary schistosomiasis extremely dangerous?

Confluent granulomas followed by ulceration form around schistosome eggs in the urinary bladder wall; this process is a precancerous condition.

What causes the development of elephantiasis in filariasis?

Filariae cause inflammation and sclerosis of the lymphatic vessels, leading to complete blockade of lymph outflow and massive tissue edema (lymphedema).

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What else to study on this topic

Pathogenesis of pannus formation in trachoma
Histological structure of leprosy granulomas in various forms
Mechanisms of portal hypertension in severe schistosomiasis
Specifics of nervous system involvement in Hansen's disease (leprosy)
Morphological picture of anthrax and other quarantine infections

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Salmonellosis