MYCOLOGY

Question: 01
▪ What is fungus and classification it according to morphology.
▪ Common characteristics of fungi.
▪ State the difference between bacteria and fungus.
Fungus: Fungus are chlorophyll free unicellular of multicellular eukaryotic organisms
reproduce by sexual and asexual spore formation.
Characteristics of fungus:
✓ Fungus are eukaryotic organisms.
✓ The fungal cell wall consists primarily of chitin, a polysaccharide.
✓ The fungal cell membrane consists of ergosterol.
✓ Fungus are chlorophyll free unicellular of multicellular.
✓ Fungus reproduces by sexual and asexual spore formation.
Morphological classification with characteristics of fungus:
Morphological type Characteristics Examples
I. Yeast ✓ Unicellular ▪ Cryptococcus neoformans
✓ Spherical or elliptical
✓ Reproduce by budding or binary fission
II. Yeast like ✓ Reproduce by budding ▪ Candida albicans
III. Moulds ✓ Multicellular ▪ Dermatophytes
✓ Microscopic filaments known as hyphae ▪ Rhino-sporidium seeberi
✓ Reproduction by sexual and asexual spore
IV. Dimorphic Two forms: ▪ Histoplasma capsulatum
✓ Mould form in saprophytic, free-living
stage at room temperature (25-27oC)
✓ Yeast form in host tissue at body
temperature (37oC)
Differentiation between fungi and bacteria:
Features Fungi Bacteria
1. Nucleus Eukaryotic Prokaryotic
2. Mitochondria Present Absent
3. Endoplasmic reticulum Present Absent
4. Cell membrane Sterols Cholesterol
5. Cell wall Chitin Peptidoglycan
6. Spores For Reproduction Endospores For Survival
7. Replication Binary Fission/Budding Binary Fission
8. Ribosomes 80 S 70 S

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Question: 02
▪ What are the dermatophytes and mention it clinical types.
▪ What is candidiasis? Write down the predisposing factors of candidiasis.

Dermatophytes: Dermatophytes are fungi that can cause infection of the skin, hair and nails
due to their ability to utilize keratin.
Dermatophytes: Epidermophyton, Trichophyton, Microsporum.
Clinical classification of Dermatophytes/ ringworm (according to site):
✓ Scalp – tinea capitis ✓ Beard area – tinea barbae
✓ Feet – tinea pedis ✓ Groin – tinea cruris
✓ Hands – tinea manuum ✓ Body including trunk and arms – tenia corporis
✓ Nail – tinea unguium

Candidiasis: Candida is an opportunistic fungal agent. Disease caused by Candida is called

Candidiasis.
Predisposing factors of candidiasis:
✓ Immunodeficiency diseases: AIDS, Malignancy.
✓ Drug: Broad-spectrum antibiotics, steroid, anticancer drug, prolonged use of
contraceptive pill.
✓ Endocrine: Diabetes mellitus.
✓ Physiologic: Pregnancy, extreme age (old age and infancy).
✓ Traumatic: Brun, maceration.
✓ Others: Indwelling catheters.

Question: 03
▪ Laboratory diagnosis of cutaneous mycoses.
▪ Laboratory diagnosis of ring worm infection.
Laboratory diagnosis of cutaneous mycoses/ of ring worm (dermatophyte) infection:
Specimen collection: Isolation and identification from culture:
✓ Skin – Scrapping Specimen is incubated in Sabouraud’s dextrose
✓ Nail – Clipping agar media at 25-30oC for 3-4 weeks.
✓ Hair – Pulcking Finding:
Microscopic examination: o Naked eye:
✓ Skin – 10% KOH for at least 1 hour ✓ Colour: Green, red, white and brown.
✓ Nail – 20% KOH for at least 10 hours ✓ Texture: Cottony, powdery and velvety
✓ Hair – 40% KOH for at least 10 hours appearance.
Findings: o Microscopic examination from colony:
o Skin and nail: Septate hyphae with arthrospore. ✓ Microconidia and macroconidia.
o Hair: Ectothrix and endothrix.

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Question: 04
▪ Name some systemic fungi agents with the disease produces by them.582
▪ Name systemic and opportunistic fungal agents with the produced by them.582,585
▪ Write in short about opportunistic mycosis.

Systemic / Deep fungi:

Systemic fungal agents Diseases
Histoplasma capsulatum Histoplasmosis
Coccidioides Coccidioidomycosis
Para-coccidioides brasiliensis Para-coccidioidomycosis
Blastomyces dermatitidis Blastomycosis
Opportunistic fungi/ mycoses: The fungal infections which does not occur in an immune-competent
person, but occur when the body is immunocompromised, are called Opportunistic fungi/ mycoses.
Opportunistic fungi:
Opportunistic fungal agents Diseases
Candida albicans Different forms of candidiasis
Cryptococcus neoformans Cryptococcosis
Aspergillus fumigatus Aspergillosis
Mucor Mucor mycosis
Short note about opportunistic mycosis:
Opportunistic fungal agents and write something about candida.
Question: 05
▪ Write down the procedure of collection of skin scraping smear for fungus.
▪ How will you collect the specimen for diagnosis a case of ring-worm.
Collection of skin scraping for Fungal Culture:
Equipment: Sterile container, sterile disposable scalpel blade with handle or glass slide, adhesive
tape and alcohol swab.
Specimen Collection:
1. Stretching the skin, scrape the outer periphery of the lesion with the
blade/glass slide perpendicular to the skin surface.
2. Collect all of the skin material into a sterile container.
3. Remove adherent scrapings from the blade/glass slide by rubbing against the
edge of the container. Do not place the blade in the container with the
scrapings. Specimens will not be processed if received in the laboratory with
the blade remaining in the sterile container.
4. Secure the top of the sterile container firmly.
5. Label the sterile container with the patient’s full name, date, time and site of
collection.
6. Store the specimen at room temperature and deliver to the laboratory on
the day of collection.
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Specimen Collection another way to write:
Hair:
1. At least 10-12 affected hair with the base of the shaft intact should be collected with forceps
2. Place in sterile container
Nails:
1. Remove nail polish, if present.
2. Wipe nail with 70% alcohol using gauze (not cotton)
3. Clip a generous portion of the affected area plusscrapings of the excess keratin under the nail
4. Place in sterile container
Skin:
1. Gently scrape the surface of the skin at the actual margin of the lesion. Do not draw blood
2. Place scrapings between two clear glass slides
Sputum:
1. Collect early morning specimen under direct supervision of a nurse or physician
2. The patient should or gargle with antiseptic solution to rinse superficial flora.
3. Instruct patient to cough deeply to produce sputum expectorate.
4. Saliva should NOT be submitted
Tissue:
1. Submit a sterile container
2. Add a few drops of sterile saline to keep small scrapings moist.
3. Do not allow tissue to dry out.
Question: 06
▪ Procedure of stool slide preparation.
▪ How can you make a saline and iodine preparation of stool.
Preparation of stool slide/ Preparation of normal saline smear in stool:
Method: Slide preparation
Materials required:
- Glass slide - Dropper - Microscope
- Cover slip - Stirrer - Marker
Reagent: normal saline.
Sample: Fresh or preserved stool.
Procedure:
- Take a clean and dry glass slide.
- Take one drop normal saline on the glass slide.
- Add small amount of stool.
- Mix gently by Stirrer.
- Cover with cover slip.
- Now ready for microscopic examination.
Result: Pus cells: 1-3/HPF, RBCs: 0-2/HPF.
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Preparation of iodine smear in stool:
Method: Stool slide preparation
Materials required:
- Glass slide - Dropper - Microscope
- Cover slip - Stirrer - Marker
Reagent: Lugol’s iodine.
Sample: Fresh or preserved stool.
Procedure:
- Take a clean and dry glass slide.
- Take one drop Lugol’s iodine solution on the glass slide.
- Add small amount of stool.
- Mix gently by Stirrer.
- Cover with cover slip.
- Now ready for microscopic examination.

Question: 07
▪ Name some antifungal agent.
▪ What are the divical form of pityriasis versicolor?
▪ What are the clinical features of pityriasis versicolor.
▪ What is thrush?
▪ What are moulds and hyphae?

Antifungal agent: An antifungal agent is a drug that selectively eliminates fungal pathogens
from a host with minimal toxicity to the host.
Antifungal drugs/ agent:
1. Clotrimazole 4. Econazole 7. Nystatin
/Clo.tri.ma.zole/ /eco.na.zole/ 8. Amphotericin
2. Miconazole 5. Terbinafine
/mico.na.zole/ /ter.bi.na.fine/
3. Fluconazole 6. Ketoconazole
/fluco.na.zole/ /keto.co.na.zole/

Thrush: Thrush is a common yeast infection that affects men and women. It's usually harmless
but it can be uncomfortable and keep coming back.

Moulds And Hyphae: Molds are multinucleated, filamentous fungi composed of hyphae. A
hypha is a branching, tubular structure from 2-10 µm in diameter and is usually divided into cell-like
units by crosswalls called septa. The total mass of hyphae is termed a mycelium.

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Pityriasis versicolor:
✓ Pityriasis versicolor is a common yeast infection of the skin, in which flaky discoloured
patches appear on the chest and back.
✓ Pityriasis versicolor is a common fungal skin infection. It's sometimes also called tinea
versicolor.
✓ Clinical features of pityriasis versicolor include either hyperpigmented or hypopigmented
finely scaly macules. The most frequently affected sites are the trunk, neck, and proximal
extremities.

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