Systemic Mycoses

Microbiology /Parasitology Systemic Mycoses 10 January 08

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Systemic Mycoses True Systemic (Endemic) Mycoses • Coccidioidomycosis • Histoplasmosis • Blastomycosis • Paracoccioidomycosis True Systemic Mycoses General Features: • Causative Agents thermally dimorphic fungi that exist in nature, soil • Geographic distribution varies

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Etio: Coccidioides immitis Location: Confined to Southwestern US, Northen Mexico, Central and South America Micr.: Tissue (37°C): Spherules filled with endospores 25°C: hyphae, barrel-shaped arthroconidia Pathogenesis: • Inhalation of the infectious particle, arthroconidia and spherule formation in vivo • Engulfment within phagosomes by alveolar MQs • Activation of macrophages ------ phagosome-lysosome fusion ----- killing • Immune complex formation ⇒ Deposition leading to local inflammatory reactions ⇒ Immunosuppression resulting from the binding of complexes to cells bearing Fc receptors Clinical Findings: PRIMARY INFECTION • Asymptomatic in most • Fever, chest pain, cough, weight loss • Nodular lesions in lungs SECONDARY (DISSEMINATED) INFECTION ( 1%) • Chronic / fulminant • Infection of lungs, meninges, bones and skin

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Inhalation  pulmonary infection  dissemination No evidence of transmission among humans or animals Otherwise healthy individuals are infected COCCIDIOIDOMYCOSIS

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Chronic cutaneous coccidioidomycosis showing granulomatous lesion of the face, neck, and chin. Extension of pulmonary coccidioidomycosis showing a large superficial, ulcerated plaque.

Diagnosis: Samples: Sputum, tissue 1. Direct examination (KOH; H&E) • Spherule 2. Culture

Elyu, Brim & Virns

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SDA :Mould colonies at 25°C

Spherule production in vitro by incubation in an enriched medium at 40°C, 20% CO2

Direct microscopy of skin scrapings from a cutaneous lesion mounted in 10% KOH and Parker ink solution showing characteristic endosporulating spherules (sporangia) of Coccidioides immitis. The presence of spherules with endospores is diagnostic. Tissue section showing typical endosporulating spherules of Coccidioides immitis. Young spherules have a clear centrewith peripheral cytoplasm and a prominent thick-walled. Endospores (sporangiospores) are later formed within the spherule by repeated cytoplasmic cleavage. Rupture of the spherule releases endospores into the surrounding tissue where they reinitiate the cycle of spherule development. Culture of coiccidioides immitis shoiwing a suede-like to downy, greyish white colony with a tan to brown reverse

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Serology Tube precipitin (IgM) test Complement fixation

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Skin Test ( Coccidioidin and Spheruline antigens) Negative results may rule out the diagnosis

Treatment: Symptomatic treatment only (Primary infection) • Amphotericin B • Itraconazole • Fluconazole (particularly for meningitis) HISTOPLASMOSIS Etio: Histoplasma capsulatum Natural reservoir: soil, bat and avian habitats Location: May be prevalent all over the world, but the incidence varies widely (most endemic in Ohio, Kentucky, Mississippi) Micr: Yeast cell in tissue (37°C) Hyphae, micronidia and macronidia (tuberculate chlamydospore) at 25°C Pathogenesis: • Inhalation of micronidia / primary cutaneous inoculation • Conversion to budding yeast cells • Phagocytosis by alveolar macrophages • Restriction of growth or dissemination to RES by bloodstream • Suppression of cell-mediated immunity Clinical Findings: PULMONARY INFECTION • Asymptomatic (95%) / mild / moderate / severe /chronic cavitary DISSEMINATED INFECTION

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Microbiology/Parasitology – Systemic Mycoses by Dra de Castro •

RES (liver, spleen, lymph nodes, bone marrow), mucocutaneous infection PRIMARY CUTANEOUS INFECTION o

Histoplasmosis of the lower gum showing ulcer around base of the teeth.

Diagnosis: Samples: Sputum, tissue, bone marrow, CSF, blood 1. Direct Examination: Giemsa / Wright Intra- and extracellular yeast cells 2. Culture: Mould at 25°C Conversion to yeast on an enriched medium at 37°C

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Tissue morphology of H. capsulatum var. capsulatum (left) showing numerous small narrow base budding yeast cells (1-5µm diameter) inside macrophages and H. capsulatum var. duboisii (right) showing larger sized budding yeast cells (5-12µm). Interpretation: As a rule, a positive direct microscopy demonstrating characteristic yeast-like cells from any specimen should be considered significant.

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ASYMPTOMATIC INFECTION PULMONARY INFECTION CHRONIC CUTANEOUS INFECTION • Subcutaneous nodules, ulceration DISSEMINATED INFECTION • Skin, bone, GUT, CNS, spleen PRIMARY CUTANEOUS INFECTION • Haematogenous spread gives rise to cutaneous lesions in over 70% of patients. These tend to be painless and presden t either as a raised verrucous lesions with irregular borders, or as ulcers. The face, upper limbs, neck and scalp are the most frequent sites involved. Diagnosis: Samples: Sputum, tissue 1. Direct microscopic exam: KOH, H&E • Yeast cells; bud is attached to the parent cell by a broad base

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Tissue sections showing large, broad-base, unipolar budding yeast-like cells, 8-15 µm in diameter. Note: tissue sections need to be stained by Grocott′s methenamine silver method tp clearly see the yeast-like cells, which are often difficult to observe in H&E preparations.

3. Serology Complement Fixation

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Skin Test (Histoplasmin antigen): Limited diagnostic value. AFRICAN HISTOPLASMOSIS

Etio: Histoplasma capsulatum var. duboisii Differentiation from Classical Histoplasmosis • Larger, thick-walled yeast cells • Pronounced giant cell formation in infected tissue • Diminished pulmonary involvement • Greater frequency of skin and bone lesions Treatment:  Not required for several cases • Amphotericin B • Itraconazole • Surgical resection of pulmonary lesions BLASTOMYCOSIS Etio: Blastomyces dermatitidis Location: America, Africa, Asia Micr.: Yeast at 37°C −−− bud is attached to the parent cell by a broad base Hyphae and conidia at 25°C Pathogenesis: • Inhalation of infectious particles • Primary cutaneous inoculation • Infiltration of macrophages and neutrophils and granuloma formation • Oxidative killing mechanisms of neutrophils and fungicidal activity of macrophages Clinical Findings:

2. Culture:

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Mould at 25°C

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Skin Test (Blastomycin antigen) Limited / no diagnostic value.

Conversion to yeast on an enriched medium at 37°C 3. Serology: • Immunodiffusion test • ELISA to detect antibodies to exoantigen

Treatment: • Amphotericin B • Itraconazole • Fluconazole • Corrective surgery PARACOCCIDIOIDOMYCOSIS Etio: Paracoccidioides brasiliensis Location: Central and South America Pathogenesis: Inhalation of conidia ∗∗ The infection is more common in males. Micr.: At 37°C (in tissue): multiply budding yeasts; the buds are attached to the parent cell by a narrow base At 25°C: hyphae and conidia Determinants of Pathogenicity: • The fungus has a protein in its cytoplasm which binds only to estrogen but not to testosterone; this binding prevents conversion to yeast form at 37°C. • Yeast cell wall polysaccharides (alpha-glucan) stimulate granuloma formation. Clinical Findings: ASYMPTOMATIC INFECTION

Microbiology/Parasitology – Systemic Mycoses by Dra de Castro LATENT FORM (duration variable) SYMPTOMATIC INFECTION • Noduler lesions in lungs • Dissemination to other organs (rare) Mucocutaneous para coccidioidomycosis showing extensive destruction of facial features. Mucocutaneous paracoccidioidomycosis showing an ulcerated lesion on the pharyngeal mucosa.

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Diagnosis: Samples: Sputum, tissue 1. Direct microscopic exam: KOH, H&E • multiply budding yeasts; the buds are attached to a parent cell by a narrow base 2. Culture: Mould at 25°C

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Conversion to yeast on an enriched medium at 37°C Multiple, narrow base, budding yeast cells “steering wheels” of P. brasiliensis GMS stained lung section (left) and phase contrast of cells from a culture (right). Interpretation: As a rule, a positive direct microscopy demonstrating the presence of a large, 20-60 µm, round, narrow base budding yeast cells with multiple budding “steering wheels” from any specimen should be considered significant.

3. Serology: Immunodiffusion Complement Fixation Treatment: • Amphotericin B • Ketoconazole • Itraconazole • Sulfonamides Maraming salamat kina kate ng 2c sa trans, hehe.

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