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Morphology of Fungi

Chapter · January 2018

DOI: 10.5005/jp/books/14206_19

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Upasana Bhumbla
Adesh Institute of Medical Sciences and Research
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Chapter 18 Morphology of Fungi

Aim: To make a Lactophenol cotton blue preparation of the given fungal culture and report.
Requirements: Lactophenol cotton blue (LCB) solution.
Composition of Lactophenol cotton Blue:
•• Phenol crystals – 20 g
•• Lactic acid – 20 mL
•• Glycerol – 40 mL
•• Distilled Water – 20 mL
•• Cotton Blue – 0.075 g
The phenol crystals are dissolved in the liquid by gently warming. Add dye to it.

Procedure:
1. A drop of Lactophenol cotton blue is placed on the center of a clean slide.
2. Using a sterile needle, a small portion of the pure fungal colony in the given culture is transferred to the drop of LCB
slide.
3. It is then teased apart with dissecting needles.
4. A cover slip is carefully placed on the preparation avoiding air bubbles.
5. After reducing the light, by lowering the condenser and using the concave mirror, the preparation is first screened
under low power to visualise the hyphae and the conidia.
6. It is then visualized under high power in order to identify the fungus.
KOH mount: Potassium hydroxide (KOH) mount is a very useful test for the laboratory diagnosis of fungal infection of
tissues especially skin, hair and nails. KOH separates the fungal elements from intact cells as it digests the protein debris and
dissolves cement substances that holds the keratinized cells together and makes it easy to visualize under the microscope.
Requirements:
1. 10% KOH
2. Coverslip
3. Glass slide
4. Needle
5. Bunsen flame
6. Specimen
 130 Workbook for Practical Microbiology

KOH Procedure 
•• Place the specimens like epidermal scales, nail, hair, skin scrapping or tissue on a clean glass slide.
•• Pour a drop of 10% KOH on the specimen and place a converslip over it.
•• Heat the slide gently over flame.
•• Leave the slide for 5–10 minutes.
•• Examine the slide under microscope.
 Morphology of Fungi 131
Enumerate various fungi based on their morphology and draw suitable diagrams

1. Cryptococcus neoformans:
•• Capsulated yeast cell
•• Demonstration of capsule by—negative staining by India ink
•• Causes opportunistic infection Cryptococcosis
•• CSF sample is taken

2. Candida albicans:
•• Ovoid or spherical budding yeast cells are seen on Gram
staining
•• Pseudohyphae—tube like elongations seen in tissue for
invasion.
•• Can cause opportunistic infections
•• Germ tube test or Reynolds Braude phenomenon is seen

3. Trichophyton:
•• Segmented hyphae with conidia are seen on lactophenol cotton
blue (LPCB) stain
•• Microconidia—abundant, arranged along hyphae
•• Macroconidia—scanty with blunt edges
•• Infects skin, hair and nail

4. Microsporum:
•• Segmented hyphae
•• Microconidia are few and plenty of macroconidia are present
•• Macroconidia—large, multicellular, spindle shaped
•• Infects skin and hair
132 Workbook for Practical Microbiology

5. Epidermophyton:
•• Microconidia are absent
•• Macrocnidia are abundant—multicellular, pear shaped
•• Infects skin and nails

6. Madurella mycetomatis:
•• Pus from sinuses containing granules or grains is processed
•• Granules—microcolonies of fungus
•• LCB mount of crushed granules

7. Rhinosporidium:
•• Large number of fungal spherules are seen
•• Each spherule matures into a sporangium 350 µm in size
•• Thousands of endospores(6–9 µm) in each sporangium
•• Rhinosporidium seeberi—mainly seen as nasal mass

8. Aspergilus niger:
•• Grossly, colonies are black are in color
•• Septate hyphae with condiophores are seen
•• Vesicle is globular with uniseriate/biseriate sterigmata
 Morphology of Fungi 133

9. Aspergillus fumigatus:
•• Grossly colonies are dark green in color
•• Vesicle is conical in shape with uniseriate sterigmata
•• Septate hyphae with condiophores are seen

10. Penicillium:
•• Grossly colonies are blue-green in color with white border and
a powdery surface
•• Septate hyphae with branched conidiophores, with two
rows of sterigmata bearing chain of spores—brush or broom
appearance

11. Mucor:
•• Broad aseptate hypahe are seen
•• Sporangiophores are seen with sporangia and spores
•• Rhizoids are absent

12. Rhizopus:
•• Broad aseptate hyphae are seen
•• Rhizoids are present
134 Workbook for Practical Microbiology

Q1. What are dermatophytes and classify them?

Q2. Name the fungi responsible for Subcutaneous mycotic infections.

 Morphology of Fungi 135
Q3. What are the various causative agents of Mycetoma? Mention the differences between bacterial and fungal
(Eumycotic) Mycetomas.

Q4 What are dimorphic fungi? Give examples.

136 Workbook for Practical Microbiology

Q5. Mention the various specimens, possible fungal pathogens and their methods of demonstration in the following
clinical conditions:
Disease Specimen Possible fungal pathogens Method of demonstration
Dermatophytosis Skin, hair and nail

Meningitis CSF

Keratomycosis Corneal scrappings

Otomycosis Ear swab

Nasal polyps Nasal mucosa scrappings

Resp. tract Infection Sputum

Vaginitis Vaginal swab

Mycetoma Pus with granules

Systemic mycoses Sputum, bone marrow biopsy,

blood
 Morphology of Fungi 137
Q6. Mention some media used for the isolation of fungi in the laboratory.

Q7. What is the composition of Sabouraud’s Dextrose Agar (SDA)?

 138 Workbook for Practical Microbiology

Q8. What are the antimicrobial agents added to SDA.

(a) While isolating dermatophytes?

(b) While isolating fungi causing systemic infections?

Q9. What is ‘ID’ reaction?

Q10. What are Mycotoxins? Give any two examples

 Morphology of Fungi 139
Q11. What are opportunistic fungal infections? Mention the various conditions that predispose to such infections.

Q12. What are dematiaceous fungi? Give examples.

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