Bacterial, spirochete, and protozoan infections

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Chapter 17

Bacterial, spirochete, and protozoan infections

Dirk M. Elston

An infectious disease atlas can be found in the on-line content for this book.

Bacterial diseases

Impetigo

Key features

• Neutrophilic crust

• Chains or clusters of cocci

Impetigo recruits neutrophils to the stratum corneum. Organisms are commonly visible in hematoxylin and eosin sections. Gram stain and culture may be required.

Differential Diagnosis

Collections of neutrophils within the stratum corneum: psoriasis, tinea, impetigo, Candida, seborrheic dermatitis, syphilis (PTICSS)

Fig 17-1 Impetigo

Bullous impetigo

Key features

• Subcorneal bulla

• Acantholysis in granular layer

Differential Diagnosis

Staphylococcal scalded-skin syndrome and pemphigus foliaceus demonstrate acantholysis at the same level.

Fig 17-2 Bullous impetigo

Ecthyma gangrenosum is usually a manifestation of Pseudomonas sepsis.

Rhinoscleroma

Key features

• Sheets of plasma cells

• Russell bodies

• Mikulicz cells (resemble globi of leprosy)

Rhinoscleroma is caused by Klebsiella rhinoscleromatis. The inflammatory infiltrate is mixed, and contains many plasma cells. Russell bodies are plasma cells filled with bright pink immunoglobulin (“pregnant plasma cells”). The nucleus may no longer be visible. Mikulicz cells are histiocytes containing large round collections of bacilli.

Fig 17-7 Rhinoscleroma

Chancroid

Key features

• Ulcer

• Zone of necrosis, fibrin, and neutrophils at surface

• Granulation tissue

• Many plasma cells below granulation tissue

• Gram stain and culture may demonstrate bacteria

Fig 17-8 Chancroid

Granuloma inguinale

Key features

• Pseudoepitheliomatous hyperplasia with neutrophilic abscesses

• Organisms within histiocytes (Donovan bodies)

The organism may be seen best in very thin, plastic-embedded sections, processed as for electron microscopy.

Differential Diagnosis

Pseudoepitheliomatous hyperplasia with intraepidermal pustules (PEH and pus): “Here come big green leafy veggies”:

• Here – halogenoderma

• Come – chromomycosis

• Big – blastomycosis

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Bacterial, spirochete, and protozoan infections

Bacterial, spirochete, and protozoan infections

Bacterial diseases

Impetigo

Bullous impetigo

Suppurative folliculitis

Botryomycosis

Pitted keratolysis

Erythrasma

Ecthyma gangrenosum

Rhinoscleroma

Chancroid

Granuloma inguinale

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