medical mycology

05/02/2023 Mohammad Mukhit Kazi, Lecturer SDCH Pune

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Classification, Lab diagnosis

and Important diseases caused

by Fungi


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ObjectivesTo know about important characteristics of fungi

To know various classification systems

To know medically important fungi

To know the lab diagnosis of fungi

To know treatment of fungal diseases


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Mycology• Study of fungi – mycology

• Mykos – mushroom

• All fungi are eukaryotic

• Natural habitat- soil, water and decaying organic debris

• Obligate or facultative aerobe

• Chemotrophic organisms


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• Differences from bacteria

– Posses rigid cell wall

– Contain chitin, mannan and polysacharide

– Cytopalsmic membrane contain sterols

– True nuclei with Nuclear membrane, mitochondria and endopalsmic reticulum

– Unicellular or multicellular

– Divide by asexually, sexually or by both


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Classification

A. Taxanomic classification

Phyllum Thallophyta Four calsses of fungi

B. Morphological classification

Yeasts Yeasts like fungi Moulds Dimorphic fungi


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Thallophyta

ThallophytaIrregular plant masses lacking definite root, stem and leaf structures

Fungi Algae

(No chlorophyll) (Chlorophyll)

4 classes

Zygomycetes Ascomycetes Basidiomycetes Deuteromycetes or fungi imperfecti

• Lower fungi having non-septate hyphae• Forms asexual spores sporangiospores• Sexual spores zygospores and oospres

• Septate hyphae• Sexual spores (ascospores) are present within the sac or ascus

• Septate hyphae•Sexual spores are basidiospores on a basidium

• Septate hyphae•Lack a known sexual state. Most fungi medically important fungi belongs to this class


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Yeasts

i. Round to oval unicelluarii. Reproduce by buddingiii. Creamy mucoid coloniesiv. E.g. Cryptococcus neoformans


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Yeasts like fungi

• Partly as yeasts and partly as elongated budding cells

• Germ tube to demonstrate pseudohyphae


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Moulds

1. Grow as branching filaments – hyphae

2. Hyphae septate or nonseptate

3. Continue growth called as mycelium

4. E.g Dermatophytes, Aspergillus, Penicillium and Rhizophus


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Dimorphic fungi

• They exists as yeasts in host tissue and in cultures as mycelial growth

• Blastomyces dermatitidis, Paracoccidioides, Coccidiodes immitis, Histoplasma, Sporothrix


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Reproduction and sporulation• Sexual spores – oospres, ascospores,

zygospores and basidiospores• Vegetative spores – – Blastospores:formed by budding from parent cell

– Arthrospores: cross septa into hyphae

• Aerial spores: Conidiospores, Microconidia, Macroconidia, Sporangiospores


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Laboratory Diagnosis

A. Direct microscopy– KOH preparation– Gram staining– India ink preparation

B. Culture- SDA

C. Slide culture test


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Classification of fungal diseases

A. Superficial mycoses- skin nails hair

B. Subcutaneous mycoses – myetoma

C. Systemic mycoses - aspergillosis


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Dermatophytes

• They infect superficial keratinized tissue (skin, nail and hair) without involving tissue

• They break down and utilizes keratin• Incapabale of penetrating subcutaneous tissue• Cause dermatomycoses also known as

ringworm


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Cylindrical macroconidia

Fusiform macroconidia

Club shaped macroconidia


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Classification

– Trichophyton - hair, skin and nail

– Microsporum – hair , skin

– Epidermophyton – skin and nail

Lab diagnosis:

Specimen: skin, hair or nail Direct microscopy – LPCB mount Culture

Treatment


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Subcutaneous Mycoses• Mycetoma : crhonic granulomatous infection of

subcutaneous tissue usually affects foot• Also known as Madura foot• Mainly in tropical countirs• Common in Tamilnadu• Caused by Actinomycetes and filamentous fungi• Enter through minor trauma• Diagnosis made by observing granules• Treatment- sulphonamides sometime amputation


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Sporotrichosis• Is nodular, ulcerating disease of skin and subcutaneous

tissue• Acces through thorn pricks or injuries• Spread through lymphatics upto regional lymph nodes • Sporothrix schenckii – dimorphic fungi• Lab diagnosis by culture


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Rhinosporidiosis• Is a chronic granulomatous disease characterized by

formation of friable polyps, usually confined to nose, mouth or eye

• Causative agent Rhinosporidium seeberi• Reported from Srilanka and India• Mode of infection is not known• Lab diagnosis done by demonstration of sporangia


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Rhinosporidiosis


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Systemic mycoses1. Histoplasmosis– Histoplasma capsulatum– Reticuloendothelial system– Source – soil with excreta of birds– Asymptomatic– Sputum, bone marrow, blood, scrapings,

biopsies– Geimsa stain or Wright stain– Culture- SDA– Amphotericin B


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2. Blastomycosis

– Blastomyces dermatitidis- dimorphic fungi

– Infection mainly to skin, bone and genitourinary tract

– Inhalation of conidia

– Asymptomatic

– Sputum, pus or scrapings

– 10% KOH, H&E stain and PAS stain

– Culture-SDA

– Amphotericin B


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3. Paracoccidiomycosis– Paracoccidioides brasilensis- dimorphic fungi– Inhalation of spores– Same

4. Coccidiodomycosis

5. Crptococcosis- Crptococcus neoformans- Inhalation of dust- Seen in immunocompromised- demosntration of capsule by india ink

6. Opportunistic mycoses- candiasis, aspergillosis, zygomycoses


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Aspergillus fumigatus


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Aspergillus terreus


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Aspergillus fumigatus


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ASpergillus niger


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Typical growth of Aspergillus spp


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ASpergillus flavus


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Mucor


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Take home message

• Fungi are eukaryotes

• Medically important fungi belongs to Fungi imperfecti or Deuteromycetes

• Sabourauds dextrose agar is used to culture

• Slide culture to demonstrate better morphological characters

• KOH mount or LPCB mount for demonstration

• Mainly opportunistic infections

• E.g. Candidiasis, Cryptococcosis, Aspergillosis

medical mycology

Healthcare