Mycology Short Notes
The topic ‘ Mycology Short Notes for MCQs’ will serve as a capsule for candidates who are participating in posts for medical lab technician, medical lab technologist, and such related fields.
Fungal infection
- Superficial infection
- Cutaneous infection
- Subcutaneous infection
- Systemic infection
- Opportunistic infection
- Superficial infection: by Malassezia furfur
- Cutaneous infection: by Dermatophytes
- Causative agents of ringworm and tinea
- Not involve living tissue
- Culture media: Sabrouand’s Dextrose Agar (SDA)
Classification depending upon site and colony characters
⇒Clinically ringworm is classified depending on the site of the body involved e.g.
- Tinea axillaries: axilla
- Tinea barbae: Beard area
- Tinea corporis: Non- hair skin
- Tinea: hair and scalp
- Tinea cruris: in groin
- Tinea pedis: foot (Athlete’s foot)
- Tinea common infection in human beings: T. rubrum
Systemic Infection
- Cryptococcus neoformans: meningitis
- Histoplasma capsulatum: pulmonary disease
- Blastomyces dermatidis: lung infection
- Cocciodioide immitis: primary lung infection
- Paracoccidiodes brasiliensis: Pulmonary disease
C. neoformans
- Yeast like fungi and monomorphic
- Reservoir: bird dropping
- Most common infection in immunocompromised patients eg. AIDS
- It contains a prominent polysaccharide capsule
- Does not produce pseudo mycelium
- Antigenically 4 types (A, B, C, and D)
- A and B are the most common infection types
- Disease: meningitis ( common), lung infection
Culture
Selective media: Birdseed Agar
Other : SDA creamy white and mucoid colony
Microscopy: Indian ink preparation
Opportunistic Mycosis
- Candida
- Aspergillus
- Pneumocystis jirovecii
- Mucor
- Penicillium
Candida albicans
Normal flora of mouth and vagina
Pathogenicity
- Oral thrush, vaginal thrush
- Infection of skin and nails
- Systemic infection
- Oral thrush is the most common infection in AIDS patients due to C. albicans
Microscopy: KOH preparation
Culture
SDA: smooth creamy white colony with yeasty odor.
Identification
“Germ tube test”
Few colonies is incubated serum for 3 hours at 37°C.
“Germ tube” formation is observed
Dimorphic fungi
Occurs in two form
- Yeast form: parasite phase: culture at 37°C
- Spores and filamentous form (mold)
- Saprophytic phase
- Culture at 22 to 25°C
Dimorphic fungi are
- Sporothrixi schenckii
- Blastomycosis
- Histoplasma
- Candida Albicans
- Paracoccidiodomycosis
- Penicillium
- Coccidioidomycosis
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Laboratory diagnosis of Fungi disease
- Microscopy
- KOH (10 %): Skin, nails, and fungal granules
- India ink: for SCF and other body fluids- negative stain shown by encapsulated fungi
- Loctophenol cotton blue. For tease amount preparation
Stain
All fungi are gram-positive
Giemsa stain → Histoplasma
PAS stain
Gomori methenamine silver stain
Mucicaramine stain
Culture
- SDA ( Sabourand’s dextrose agar)→ Commonly used media for fungi→ Slightly acidic (pH 5.6 to 6 )
- DTM (Dermatophyte test medium ) with gentamycin.
- Myscosel agar
- CMA ( Corn Meal Agar )
- BSA ( Bird Seed Agar): for Cryptococcus