Basic Microbiology - Fungal Infection Identification

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Questions and Answers

What is mycology the study of?

Bacteria

Fungi (correct)

Algae

Viruses

Which of the following fungi produces pseudohyphae?

Saccharomyces cerviciae

Aspergillus spp.

Candida albicans (correct)

Histoplasma capsulatum

What form does Histoplasma capsulatum take at room temperature?

Bacterial colony

Mould (correct)

Spore

Yeast

Who is regarded as the father of medical mycology?

Raymond Sabouraud Signup and view all the answers

For standard autoclaving, what precaution must be taken?

Maintain standard settings Signup and view all the answers

What is a common characteristic of filamentous fungi?

They are composed of hyphae Signup and view all the answers

Which specimen would NOT typically be collected for fungal infection identification?

Bone marrow Signup and view all the answers

What is the primary technique used for direct microscopic investigation of fungal specimens?

Wet mount with KOH Signup and view all the answers

Which of the following is NOT a category of fungi based on morphology?

Algae Signup and view all the answers

What safety precaution should be maintained during fungal isolation in the lab?

Using appropriate personal protective equipment Signup and view all the answers

What is the primary purpose of using Sabouraud’s Dextrose Agar (SDA) in the laboratory?

To selectively culture fungi Signup and view all the answers

Which of the following fungi are known to grow at 37°C?

Cryptococcus Signup and view all the answers

What technique is used for isolating yeast from a specimen?

Streaking technique Signup and view all the answers

Which component of Lactophenol cotton blue is responsible for staining chitin in fungal cell walls?

Methyl blue Signup and view all the answers

What is the role of phenol in the Lactophenol solution?

To kill any microorganisms Signup and view all the answers

Which of the following is NOT a component of Lactophenol?

Methanol Signup and view all the answers

What is the typical pH range of Sabouraud’s Dextrose Agar, which helps inhibit bacterial growth?

4.5 - 5.5 Signup and view all the answers

Which of the following stains can be used to observe fungi in a specimen?

Gram stain Signup and view all the answers

What essential function does lactic acid serve in the Lactophenol cotton blue preparation?

Preserving fungal structures Signup and view all the answers

Which of the following parts of the fungal specimen is typically observed using direct microscopy with KOH preparation?

Skin, hair, and nails Signup and view all the answers

What is the characteristic feature of glaborous fungal colonies?

They appear leathery or waxy with few aerial mycelium. Signup and view all the answers

Which of the following fungi are classified as rapid growers?

Saprophytic fungi Signup and view all the answers

What is meant by 'reverse pigmentation' in fungi?

Pigmentation observed on the reverse side of the colony. Signup and view all the answers

Which term describes colonies that have radial grooves from the center to the edge?

Rugose Signup and view all the answers

Slow-growing fungi may take how long to produce colonies?

11 days to 8 weeks Signup and view all the answers

Which of the following terms accurately describes a colony that appears velvety?

Resembling velvet fabrics with short aerial hyphae Signup and view all the answers

What is a defining feature of yeast-like colonies?

They resemble colonies of Staphylococcus. Signup and view all the answers

What type of fungi are categorized as intermediate growers?

Fungi that grow in 6-10 days such as dermatophytes Signup and view all the answers

What type of pigmentation characterizes hyaline fungi?

Colorless or non-pigmented Signup and view all the answers

Which characteristic best describes granular colonies?

Powdery and mostly formed by sporulating fungi Signup and view all the answers

Study Notes

Basic Microbiology - Practical No. 7: Isolation and Identification of Fungal Infection

Intended Learning Objectives (ILOs):
- Introduce common fungal media
- Introduce inoculation and incubation techniques
- Introduce fungal growth characteristics
- Introduce wet mount KOH and Lactophenol Cotton Blue (LPCB) techniques

Precautions

Wear appropriate personal protective equipment
Maintain aseptic conditions
Select the correct autoclave settings (avoid over or under sterilization)

Introduction/Background

Mycology is the study of fungi.
Fungi can infect plants and animals.
Raymond Sabouraud was a pioneer in medical mycology, his work focused on dermatophytic fungi, which is a type of fungus that infects skin and nails.
Fungi are classified into four categories based on their morphology:
- Moulds: Filamentous fungi (e.g., Aspergillus spp.)
- Yeasts: Single-celled fungi (e.g., Saccharomyces cerevisiae)
- Yeast-like: Fungi similar to yeasts that produce pseudohyphae (e.g., Candida albicans)*
- Dimorphic: Fungi that can exist as either yeasts or moulds depending on environmental conditions (e.g., Histoplasma capsulatum)
Fungal specimen collection depends on the site of infection, including hair, skin, nail clippings, sputum, blood, and biopsy specimens.

Fungal Culture Techniques

Moulds: Samples are placed in sterile petri dishes using a sterile scalpel.
Yeasts: Streaking techniques are used for yeast isolation.

Direct Microscopy (KOH Wet Mount)

This technique is used for specimens like skin, hair, and nails, and some body fluids to detect fungal infections.

Staining Techniques

Lactophenol Cotton Blue (LPCB): Used to examine fungal cell structure. LPCB contains phenol, lactic acid, and glycerol. Phenol kills microorganisms, lactic acid preserves fungal structures, and glycerol inhibits cellulolytic activity. Methyl blue stains chitin in fungal cell walls, making them visible.
Gram Stain: Used to observe fungi, along with LPCB.

Practical Procedure (Part One: Culture of Fungal Specimen)

Materials: Sabouraud's Dextrose Agar (SDA) and a loop
Procedure: Students culture yeast samples using streaking techniques on SDA and observe results.

Practical Procedure Part Two: Staining of fungi (LPCB and Gram Staining)

Materials: 1 glass slide
Procedure: Observe the prepared slide using Microscopy and note your observations.

Results (Week 5): Record Fungal Morphology

Students should record their observations of yeast and mould samples for morphology and culture

Identifying Characteristics of Fungi

Rate of Growth: Fungi are divided into rapid (less than 5 days), intermediate (6-10 days), and slow growers (more than 11 days, possibly up to 8 weeks). Examples are provided for each category.
Pigmentation: Pigmentation on the colony's surface (surface) or reverse side (reverse), is a characteristic used in the detection of microorganisms.
Colony Characteristics (Texture): Different textures include glabrous (smooth), velvety, yeast-like, cottony, and granular are helpful in the identification of fungi based on the size, shape, and texture of the fungi's colonies or culture.

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Description

This quiz covers practical techniques for isolating and identifying fungal infections. You will learn about common fungal media, inoculation, incubation techniques, and characteristics of fungal growth. Master the use of wet mount KOH and Lactophenol Cotton Blue methods while adhering to safety precautions.