Mycology-MHA-2024

What is the primary diagnostic medium for fungal cultures?

• A) Blood agar

• B) Sabouraud dextrose agar

• C) MacConkey agar

• D) Chocolate agar

Answer: B . Sabouraud dextrose agar

Which structure is characteristic of yeasts?

• A) Hyphae

• B) Sporangia

• C) Unicellular ovoid bodies

• D) Conidiophores

Answer: C. Unicellular ovoid bodies

What type of fungi cause Sporotrichosis?

• A) Dermatophytes

• B) Dimorphic fungi

• C) Yeasts only

• D) Opportunistic molds

Answer: B Dimorphic fungi

by SPOROTHRIX SCHENCKII (rose-gardener’s disease)

an example of sub cutaneous mycosis

Which fungal infection primarily affects the mucosal surfaces?

• A) Systemic mycosis

• B) Superficial mycosis

• C) Subcutaneous mycosis

• D) Opportunistic mycosis

Answer: B Superficial mycosis

What is a major virulence factor for Candida albicans?

• A) Biofilm formation

• B) Spore production

• C) Sporangium formation

• D) Flagella

Answer: A Biofilm formation

• What is the primary mode of entry for subcutaneous mycoses?

  • A) Inhalation of spores

  • B) Traumatic introduction

  • C) Direct ingestion

  • D) Bloodstream invasion
    
    

  
  

Answer: B Traumatic introduction
Explanation: Subcutaneous mycoses occur when fungal spores or mycelial fragments are introduced into the subcutaneous tissue via trauma, such as cuts or puncture wounds.

Which of the following is NOT a characteristic of Candida albicans?

• A) Forms biofilms on host tissues

• B) Produces Candidalysin toxin

• C) Causes systemic infections only

• D) Exhibits dimorphism
  
  

• Answer: C Produces Candidalysin toxin
  Explanation: Candida albicans can cause both localized infections (e.g., oral thrush) and systemic infections, especially in immunocompromised patients.

Which diagnostic method involves detecting fungal antigens in tissues using fluorescence?

• A) Direct microscopic examination

• B) Direct fluorescent microscopy

• C) Serological testing

• D) Culture on Sabouraud agar
  
  

• Answer: B Direct fluorescent microscopy
  Explanation: Direct fluorescent microscopy involves staining and observing fungal elements using fluorescence-based techniques.

What is the role of hydrolytic enzymes in fungal virulence?

• A) Promote hyphal growth

• B) Facilitate tissue penetration

• C) Enhance spore production

• D) Neutralize host immune responses
  
  

• Answer: B Facilitate tissue penetration
  Explanation: Hydrolytic enzymes, such as Aspartyl proteinases, help fungi degrade host tissue barriers, facilitating invasion and dissemination.

• an example of virulence factors of candida albicans

Which superficial fungal infection is caused by Malassezia furfur?

• A) Tinea pedis

• B) Tinea versicolor

• C) Ringworm

• D) Tinea capitis
  
  

• Answer: B Tinea versicolor
  Explanation: Malassezia furfur causes Tinea versicolor, characterized by fine scales on the skin, typically in areas like the chest and back.

What type of fungal infection is limited to the outer layers of skin and hair?

• A) Systemic mycosis

• B) Cutaneous mycosis

• C) Subcutaneous mycosis

• D) Superficial mycosis
  
  

• Answer: D Superficial mycosis
  Explanation: Superficial mycoses involve only the outermost layers of the skin, hair, and nails without invading deeper tissues.

What is the most common antifungal treatment for oral thrush?

• A) Amphotericin B

• B) Nystatin

• C) Fluconazole

• D) Ketoconazole
  
  

• Answer: B Nystatin
  Explanation: Nystatin is commonly used as a topical treatment for oral thrush and is effective because it remains localized in the mouth.

Fungi are only pathogenic in immunocompromised individuals.

Answer: False
Explanation: While many fungi are opportunistic pathogens that require impaired host defenses, there are primary true pathogens (e.g., Histoplasma capsulatum) that can infect healthy individuals.

Yeasts are multicellular fungi that form thread-like structures called hyphae.

Answer: False
Explanation: Yeasts are unicellular fungi with spherical or ovoid bodies. Hyphae are multicellular structures characteristic of molds.

Sabouraud dextrose agar is commonly used for culturing pathogenic fungi.

Answer: True
Explanation: Sabouraud dextrose agar is a medium with a slightly acidic pH (~5.6), ideal for the growth of fungi, and often supplemented with antibiotics to inhibit bacterial contamination.

Superficial mycoses affect deeper tissues such as internal organs.

Answer: False
Explanation: Superficial mycoses are restricted to the outer layers of skin, hair, and nails and do not penetrate deeper tissues.

Dimorphic fungi can exist in both yeast and mold forms depending on environmental conditions.

Answer: True
Explanation: Dimorphic fungi (all deep mycosis fungi) exhibit yeast morphology in tissue or at body temperature (37°C) and mold morphology in the environment or at lower temperatures.

The portal of entry for primary mycoses is usually the respiratory tract.

Answer: True
Explanation: Primary mycoses typically occur through the inhalation of fungal spores.

Microscopic examination of skin scrapings is not helpful in diagnosing fungal infections.

Answer: False
Explanation: Microscopic examination is a key diagnostic method for detecting fungal elements like hyphae and yeast cells.

Candidalysin, a toxin produced by Candida albicans, disrupts epithelial cells.

Answer: True
Explanation: Candidalysin is a virulence factor of Candida albicans that aids in tissue invasion by disrupting epithelial cells.

• Opportunistic fungal infections account for a majority of systemic mycoses in immunocompromised patients.
  
  

• Answer: True
  Explanation: Most systemic mycoses in immunocompromised individuals are caused by opportunistic fungi, such as Candida albicans and Aspergillus species.

  
  

Tinea versicolor is caused by a dermatophyte.

Answer: False
Explanation: Tinea versicolor is caused by Malassezia furfur, a yeast, not a dermatophyte. Dermatophytes cause other superficial infections like ringworm.

• Define mycology.
  
  

• 
  

• Answer: Mycology is the study of fungi, which includes yeasts, molds, and other fungal organisms, focusing on their biology, classification, and role in health and disease.

Name two fungal diseases caused by primary true pathogens.
Answer:

• Histoplasmosis

• Blastomycosis

Describe the morphology of hyphae.

Answer: Hyphae are multicellular, thread-like tubular structures that contain fungal cytoplasm and organelles. They form the filamentous structure of molds and are involved in nutrient absorption and growth.

List three diagnostic methods for fungal infections.

Answer:

• Microscopic examination of skin scrapings or pus.

• Culture on Sabouraud dextrose agar.

• Serology, such as latex agglutination for specific fungal antigens.

What are the key virulence factors of Candida albicans?
Answer:

• 
  

• Ability to form biofilms, which protect the fungus from the host immune system and antifungal treatments.

• Dimorphism, allowing the fungus to exist in both yeast and hyphal forms, aiding in tissue invasion.

• Hydrolytic enzymes like Aspartyl proteinases that enable tissue penetration.

• Production of the toxin Candidalysin, which disrupts epithelial cells.