This document discusses several deep fungal infections caused by dimorphic fungi, including blastomycosis, paracoccidioidomycosis, coccidioidomycosis, and histoplasmosis. It provides details on the causative agents, modes of transmission, clinical presentations, laboratory diagnosis including microscopy and culture, and treatment for each infection. The infections are acquired through inhalation of fungal spores from the soil and can affect the lungs, skin, and other organs. Laboratory diagnosis involves microscopy of specimens to identify fungal structures, culture, and serological tests. Antifungals such as amphotericin B and azoles are used as treatment.

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Topic :
Presenter : Dr. Shodhan Patel
Designation : 1st yr PG
Department : GENERAL MEDICINE
Moderator : Dr. Harshavardhan

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Deep seated fungal infections caused by fungi that are
soil saprophytes.
• Infection is accidental.
• Inhalation of air borne spores produced by moulds
• Dimorphic fungi are causative agents.
Ex: – Blastomyces dermatitidis
– Paracoccidioides brasiliensis
– Coccidioides immitis
– Histoplasma capsulatum
Definition

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Blastomycosis
(North American blastomycosis)
• Chronic infection, characterized by
• Formation of suppurative and granulomatous
lesions in any part of the body
• With a marked predilection for the lungs and skin
• Causative agent: Blastomyces dermatitidis
• Distribution:
1. North America
2. Africa
3. India- Delhi (bronchial aspirates of patient
and lungs of insectivorous bats)

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Mode of Transmission &
Epidemiology
• Source of infection- soil
It grows in moist soil rich in organic material,
forming hyphae with small pear-shaped conidia
• Mode of infection- Inhalation of the conidia •
• Primary pulmonary pathogen & resembles TB or
histoplasmosis
• M:F ratio- 4:1
• 20-50 yrs age group
• Occupation- farmers and tree cutters

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Clinical forms
• 1. Pulmonary form- Gilchrist disease, Chicago disease
– Asymptomatic
– Productive cough, weight loss, chest pain and fever
– Chronicity- resembles carcinoma, TB
– Dissemination
• 2. Cutaneous form
– Traumatic inoculation into the exposed parts
– Papule/ nodule breaks down to form a fistula-
discharge pus
• 3.Disseminated form
– In immunocompromised individuals
– Other sites affected- bones and genitourinary organs

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Laboratory diagnosis
• A. Specimen-
sputum, pus, biopsy
transport asap….
• B. Processing of specimen
1. Microscopy
2. Culture
3. Skin test
4. Ab Detection
5. Nucleic acid Detection- DNA probes
6. Animal pathogenicity – Mice, rats used
to study virulence

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1. Microscopy
1. Microscopy- KOH (10%) or Calcofluorwhite
• Yeast form:
• Large yeast cells (8-12 μm)
• Blastoconidia attached by broad base
• Double contoured wall
• Mold phase:
• Lollipop forms

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2. Culture Media
• Media : SDA, BHI agar, Blood Agar
• Two media inoculated
• incubated- one at 25°C and one at 37°C for 4 weeks.
• Colony on medium at 25°C- Fluffy and tan coloured
• LPCB - septate hyphae with oval or pyriform conidia (2-10µ)
Chlamydospores are thick walled
• Colony on medium at 37°C- Cream coloured, smooth,
• LPCB- thick walled yeast like cells, with broad based budding
• Confirmation of the isolate
• Conversion of mycelial form to yeast form on BA at 37°C
• Exoantigen analysis

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3. Skin testing
• DTH to blastomycin
• not of much value in diagnosis

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4. Antibody Detection
• Complement fixation test
• Precipitation-Immunodiffusion
• ELISA
• RIA

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Prevention & Control
• Amphotericin B & Ketoconazole- for Rx
• Surgical excision
• There are no means of prevention

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Paracoccidioidomycosis
• South American Blastomycosis or Brazilian
blastomycosis
• Definition: Chronic infection, characterized by -
>Formation of suppurative lesions in any part of the
body
->With a marked predilection for the lungs and skin
• Causative agent : P. braziliensis
• Distribution :
1. South America, esp. Brazil
2. India- not yet reported

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Mode of Transmission &
Epidemiology
• Source of infection- soil
It grows in moist soil rich in organic material,
forming hyphae with small pear-shaped conidia
• Mode of infection- Inhalation of the conidia, no
man to man transmission
• Primary pulmonary pathogen & resembles
respiratory disease
• M:F ratio- females less affected due to
estrogen
• 20-50 yrs age group

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Clinical forms
1. Pulmonary form- Gilchrist disease, Chicago disease
– Asymptomatic
– Dissemination is by hematogenous route
2. Mucocutaneous form
– Cooler areas of body such as nasal and oropharyngeal
– Ulcerative lesions seen in mouth, on lips, tongue and
conjunctiva
3. Lymphatic Paracoccidioidomycosis
– Cervical lymphadenopathy and can spread to other LN
4. Disseminated
– Seen in Immunocompromised patients
– Disease spreads to other organs specially adrenals

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Laboratory diagnosis
• A. Specimen-
sputum, pus, biopsy, bronchoalveolar lavage transport
asap….
• B. Processing of specimen
1. Microscopy
2. Culture
3. Skin test- paracoccidioidin
4. Ab Detection- CFT, ELISA, counter
immunoelectrophoresis
5. Nucleic acid Detection- DNA probes, PCR
6. Animal pathogenicity – Mice, rats used to study
virulence

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1. Microscopy- KOH (10%) or
Calcofluorwhite
• Yeast form:
• Yeast forms with multiple buds encircling
mother cell.
• Mariner’s wheel or pilot’ wheel or mickey
mouse cap appearance
• 15-30µ
• Narrow based budding

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• Mold phase:
Lollipop forms

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2. Culture
• Media : SDA, BHI agar, Blood Agar
• Two media inoculated and incubated- one at 25°C and one
at 37°C.
• Slow growth- 6 weeks
• Colony on medium at 25°C- Fluffy and tan coloured
• LPCB- septate hyphae which are sterile (no conidia)
• Colony on medium at 37°C- Cream coloured, smooth,
• LPCB- mariner’s wheel
• Confirmation of the isolate
– Conversion of mycelial form to yeast form on BA at 37°C
– Exoantigen analysis

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Treatment
• Itraconazole,
• fluconazole with amphotericin B
• ketoconazole

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Coccidioidomycosis
• Causative agent- Coccidioides immitis
• Dimorphic fungus
• Primary pulmonary pathogen
• Distribution
Endemic in southwest USA and northern
Mexico

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Clinical features
• Majority – asymptomatic
• Pulmonary disease which resembles mild
influenza like fever (Valley fever) to
Pneumonia
• Dissemination- uncommon but highly fatal

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Laboratory diagnosis
• Specimens
• Sputum
• Pus
• Biopsy

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Direct examination- Microscopy
• Yeast form
• Appears as a spherule(15-75µm in diameter)
• Thick double walled refractile wall filled with
endospores.
• Each endospore- spherule.
• Mycelial form
• Pseudohyphae which fragments into
arthrospores- highly infectious.

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Culture
• SDA or BHI agar with cycloheximide and
chloramphenicol
• Incubate at 37˚C and 25 ˚C
• Warning
arthrospores are highly infectious- arthrospores
are borne, never use petridishes for culture

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Skin test
• DTH (similar to tuberculin)
• Ag- coccidioidin
• Interpretation positive test (5mm induration
within 48 hrs)
• Endemic areas test not useful

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HISTOPLASMOSIS
• Also k/a Reticuloendothelial cytomycosis/
Caver’s disease/ Spelunker’s disease/
Darling’s disease
• Causative agent- H. capsulatum
• Dimorphic fungus
• Disease of Reticuloendothelial system
• Intracellular parasite
• Distribution- Worldwide, most common in
America

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Source of infection
• Soil enriched with excreta of birds or bats
• Inhalation of spores
• Reticuloendothelial system.. How???
• Lymphadenopathy
• Hepatospleenomegaly
• Fever and anemia

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Clinical features
• Majority – asymptomatic
• Some- pulmonary disease- resembles
tuberculosis
• Dissemination
Any skin or mucosal lesions??
• Granulomatous and/ or
• Ulcerative lesions

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Laboratory diagnosis
• Specimens
• Sputum
• Bone marrow aspirates
• Peripheral blood
• Skin scrapings
• Lymph node of biopsies and biopsy of other
organs

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Direct examination- Microscopy
• Staining: Giemsa or Wright stains
• H.capsulatum appears as small oval yeast cells,
(2-4µm in diameter) packed within the cytoplasm
of macrophages or monocytes.

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Culture
• SDA or BHI agar with cycloheximide and
chloramphenicol
• Incubate at 37˚C and 25 ˚C
• Yeast forms- 37 ˚C
• Mycelial forms- large thick walled spherical
spores with tubercles or finger like projections at
25 ˚C

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Serological tests
• After two weeks of infection- antibodies detected
• Latex agglutination test
• Precipitation test
• Complement fixation test
Rise in the antibody titre- progressive disease

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Histoplasmin skin test
• DTH (similar to tuberculin)
• Ag- Histoplasmin
– Culture filtrate of Mycelial phase of
H.capsulatum
• Interpretation
positive test ---- indicates past/ present infection
• Treatment- Amphotericin-B

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African Histoplasmosis
• H. duboisii
• Africa
• Primarily involves skin and subcutaneous
tissues
• Lungs not involved.
• Morphologically similar to Mycelial phase of
H.capsulatum
• Larger and elongated yeast forms

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Opportunistic Fungal
Infections
Candidiasis > Aspergillosis > Cryptococcosis
This topic will be dealt in detail by Dr.
Srinivas

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• HARRISON’S 21ST EDITION-PRINCIPLES OF INTERNAL
MEDICINE
• Textbook of microbiology – Ananthanarayan and Paniker’s

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THANK YOU
Name : Dr. Shodhan Patel
Designation : 1st yr PG
Department : General medicine