Systemic Mycosis 06-07

Systemic Mycoses

Caustive agents  Histoplasma capsulatum  Blastomyces dermatitidis  Cryptococcus neoformans  Coccidioides immitis  Paracoccidioides brasillensis

Histoplasmosis Causative Agent Histoplasma capsulatum var capsulatum Histoplasma capsulatum var. duboisii o The organism is misnamed because:  It infects macrophages NOT plasma cells &  It is non-capsulated Morphology  Dimorphic fungus  Smallest yeast cells  Reproduce by budding

Histoplasmosis Source of Infection • Soil containing bird or bat excreta • No case to case transmission Pathogenesis • Spores are inhaled, engulfed by macrophages and develop into yeast forms • Granulomas formed in the lung which may get calcified like TB • Disseminate and may infect macrophages in RES (liver, spleen, LN & BM)

Histoplasma yeasts within macrophages

Histoplasmosis Clinical Features • In immunocompetent persons o Asymptomatic or flue-like symptoms o Chronic lesions in lungs give TB-like picture • In immunosuppressed persons o Disseminated infection o Febrile illness o Enlargement of RE system, hepatosplenomagaly o Ulcerated lesions on tongue in AIDS patients

Histoplasmosis Lab Diagnosis • Direct examination of sputum • Not helpful as few organisms in sputum • Bone marrow aspirate histology : • Oval yeast cells within macrophages by Giemsa stain • Culture on Sabouraud’s Dextrose Agar incubate at 25oC & 37oC to show dimorphic forms • Serology o An Ab titre of 1:32 with yeast phase Ags is considered diagnostic • Histoplasmin skin test: Epidemiological value only • Histopathology of BMA: to see parasitic yeast form

Oral lesions following hematogenous dissemination

Macroconidia and microconidia. Phase contrast

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microscopy, potato glucose agar, slide culture, 25C

Rough-walled macroconidia, Sabouraurd glucose agar, 25C, lactophenol cotton blue preparation.

Yeast form growing at 37C in the laboratory. Phase contrast microscopy, 37C, 630X

Histoplasmosis Treatment • Oral itraconazole • Disseminated disease o Amphotericin B o Fluconazole in meningitis • May need surgical resection of pulmonary lesions

BLASTOMYCOSIS Pathogenesis • Blastomyces dermatitidis • Dimorphic fungus Pathogenesis • Inhalation of infectious particles • Cutaneous inoculation • Infiltration of macrophages and neutrophils and granuloma formation

BLASTOMYCOSIS Clinical findings • • • • • •

Asymptomatic Pulmonary infection Chronic skin infection Subcutaneous nodule & ulceration Disseminated infection Bone, GUT, CNS, spleen

Broad based budding yeast cells, KOH, from a lung

Broad based budding and thickened cell walls and globose shape are characteristic of the yeast form of Blastomyces dermatitidis.

Colony of Blastomyces dermatitidis on Mold Inhibitory Agar after14 days, 30C.

Skin lesion following dissemination from the lungs.

The cutaneous lesion developed following dissemination of the fungus from the lungs.

Treatment • Amphotericin B • Azoles are alternative in immuocompetent patients

Cryptococcosis Causative agent Cryptococcus neoformans (5µ) o A typical yeast with a thick capsule (25µ) o Urease positive Source of infection • Pigeon or birds droppings & contaminated soil

India Ink Preparation

Cryptococcosis Pathogenesis • Capsule is the virulence factor (antiphagocytic) • Human infection by inhalation • Most infections are asymptomatic • May develop pneumonia • Disseminate to CNS causing meningitis

Cryptococcosis Clinical Features

• Disease usually affects immunocompromised • Lung infection usually asymptomatic • Cryptococcal meningitis

o Among top four life-threatening infections in AIDS

Meningitis • Intermittent headache & dizziness & vomiting • Difficulty in thinking • Slight fever • Slowly progressing to weight loss, impairment of nerves • May be difficult to diagnose in early stages

Cryptococcosis Lab Diagnosis • o o o

CSF Examination Turbid CSF Decreased glucose & increased protein Increased cell count >100 cells mostly lymphocytes o India Ink preparation  Yeast cell with a thick capsule

o Periodic acid-Schiff (PAS), detect fungal elements o Culture on SDA (grows in 48-72 hrs) o Capsular Antigen in CSF by latex agglutination

India Ink Preparation

Negative cryptococcal antigen latex test

Mixed culture of C. neoformans and C. albicans showing the distinctive brown colonies of C. neoformans, due to the selective absorption of pigment from the media, compared to the white colonies of C. albicans.

Encapsulated yeast in India ink preparation. The small round structure in the center of the white area is the yeast cell. 400X.

India ink preparation of CSF from a patient with cryptococcal meningitis showing a budding yeast cell of C. neoformans surrounded by a characteristic wide gelatinous capsule.

Raised skin lesions resulting from dissemination of the yeast in an immunocompromised patient.

C. neoformans yeasts in lung tissue. Gram stain, 100X

Cryptococcosis Treatment • Systemic fungal agents that cross blood brain barrier (BBB) • Fluconazole as prophylaxis in AIDS patients • Combined Amphotericin B & flucytosine

COCCIDIOIDOMYCOSIS Causative agent Coccidioides immitis Microscopy 37°C: Spherules filled with endospores 25°C: hyphae, barrel-shaped arthroconidia

COCCIDIOIDOMYCOSIS Pathogenesis • Inhalation of the infectious particle, arthroconidia and spherule formation in vivo • Engulfment within phagosomes by alveolar MQs • Activation of macrophages (phagosomelysosome fusion) leads to killing • Immune complex formation deposition leading to local inflammatory response

COCCIDIOIDOMYCOSIS Clinical findings PRIMARY INFECTION  Asymptomatic in most cases  Fever, chest pain, cough, weight loss  Nodular lesions in lungs SECONDARY (DISSEMINATED) INF. (1%)  Chronic / fulminant  Infection of lungs, meninges, bones and skin

COCCIDIOIDOMYCOSIS Diagnosis Samples: Sputum, tissue  Direct examination (KOH; H&E) 2. Culture √ SDA: Mould colonies at 25 °C √ Spherule production in vitro by √ incubation in an enriched medium at √ 37°C, 20% CO2

Alternating arthroconidia. Note annular frill at both ends of the separated arthroconidia. Phase contrast microscopy, tease mount from colony, 25C

Sherules and endospores in lung tissue. 1000X.

Alternating arthroconidia and hyphae. Lactophenol blue

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mount, tease preparation of mould colony, 25C

The rash is a immunologic response to the fungus. It is most commonly seen in caucasion women.

COCCIDIOIDOMYCOSIS Treatment • Amphotericin B • Itraconazole • Fluconazole (particularly for meningitis)

Features of systemic fungal pathogens Organism

Culture at 25 0C

Culture at 370C

Tissue

Primary disease

Disseminate d disease

C.neoformans

Ecapsulated yeast

Ecapsulated yeast

Ecapsulated yeast

pneunonia

C. meningitis

H. Capsulatum

Mold, tuberculate macroconid

Small yeast

Small intracellular yeast

Pneumonia, hilar adenopthay

RES enlargement

B. dermatitidis

mold

yeast

Small yeast

pneunonia

Skin and bone lesions

C. immitis

Mold, arthroconidia

spherules

spherules

Vally fever

Pneumonia, meningitis Skin & bones

P. brasiliensis

mold

yeast

yeast

pneunonia

Skin and RES

Case presentation A 52 years-old male arrived at an emergency room in a disoriented and poorly responsive state with difficult breathing. The patient’s history included poorly controlled diabetes and chronic obstructive pulmonary disease secondary to cigarette smoking. Current medications included steroids his pulmonary disease. Physical examination showed that the patient was slightly febrile, lethargic, and in respiratory failure. He showed deteriorating mental status, and a diagnosis of meningitis was considered . A lumber tap produced a CSF sample that on direct smear using calcofluor reagent showed encapsulated budding yeast. Despite aggressive therapy with amphotericin B and 5flucytosine, the patient’s condition failed to improve. The patient died on the third day of hospitalization.