Mycology and Yeast

Questions and Answers

Which characteristic distinguishes dimorphic fungi from other fungi?

They lack a cell wall.

They are incapable of forming spores.

They can exist as both yeasts and moulds depending on temperature. (correct)

They reproduce exclusively through binary fission.

Which of the following fungi is specifically known for causing cryptococcosis?

Candida auris

Cryptococcus neoformans (correct)

Trichophyton rubrum

Penicillium marneffei

Tinea versicolor is caused by which type of fungus?

Yeast (correct)

Dimorphic

Bacterial biofilm

Mould

Invasive fungal infections often stem from which of the following features?

Ability to form biofilms on medical devices. Signup and view all the answers

Which condition is primarily associated with Candida spp. infections in patients with urinary catheters?

Urinary tract infection Signup and view all the answers

Which of the following infections is NOT typically caused by Cryptococcus neoformans?

Chronic sinusitis Signup and view all the answers

What is the primary treatment for severe Candida infections in immunosuppressed patients?

Fluconazole Signup and view all the answers

What distinguishes Pneumocystis jirovecii from other yeasts?

It is non-culturable Signup and view all the answers

Which of the following is NOT a common characteristic of invasive fungal infections?

Generally mild and self-limiting Signup and view all the answers

Which method is NOT commonly used for the diagnosis of systemic yeast infections?

Biopsy for fungal culture Signup and view all the answers

Which statement is true regarding dermatophyte infections?

Skin scrapings and microscopy using KOH can reveal hyphae and arthrospores. Signup and view all the answers

What is the characteristic clinical presentation of tinea versicolor?

Hyper- or hypo-pigmented lesions with itching. Signup and view all the answers

Which of the following fungi is commonly associated with invasive infections?

Aspergillus spp. Signup and view all the answers

What does the microscopy of a skin scraping from tinea versicolor typically show?

A ‘spaghetti and meatballs’ pattern. Signup and view all the answers

Which method is primarily used to identify dermatophyte species from cultures?

Observing macroconidia and microconidia characteristics. Signup and view all the answers

What is a common complication of dermatophyte infections of the foot?

Yeast infection. Signup and view all the answers

Which of the following statements about Candida spp. is correct?

Candida spp. can be opportunistic pathogens in immunocompromised individuals. Signup and view all the answers

What is a major characteristic of Candida albicans in relation to mucocutaneous infections?

It often colonizes damaged skin and can lead to conditions such as oral thrush. Signup and view all the answers

Which of the following is a key predisposing factor for dermatophyte infections?

Minor trauma to the skin allowing fungal penetration. Signup and view all the answers

What condition is associated with angular cheilitis?

Erosions with pustules at the corners of the mouth. Signup and view all the answers

What is the role of moisture in predisposing to dermatophyte infections?

It facilitates the growth and survival of dermatophytes on the skin. Signup and view all the answers

Which population is NOT at increased risk for developing oral thrush?

Healthy adults with robust immune systems. Signup and view all the answers

What is Tinea Versicolor primarily caused by?

Malassezia furfur. Signup and view all the answers

Which statement is true regarding invasive fungal infections?

They often require antifungal medications to manage. Signup and view all the answers

In what way do Candida species behave in the skin and environment?

They can act as commensals on skin and mucous membranes. Signup and view all the answers

How does rapid colonization of Candida albicans occur on the skin?

It occurs rapidly in damaged skin or compromised environments. Signup and view all the answers

Study Notes

Dimorphic Fungi

Fungi that can exist as both yeast and mould depending on temperature.
Includes systemic pathogens like Histoplasma capsulatum.
Geographically limited in distribution, affecting certain regions.

Systemic Yeast Infections

Commonly caused by Candida species.
Urinary tract infections often related to urinary catheters.
Endocarditis risks increase with prosthetic heart valves and IV drug use.
Septicemia occurs in immunosuppressed individuals, potentially leading to chronic disseminated candidiasis.
Disseminated candidiasis can affect solid organs and be detected in eye examinations.

Diagnosis of Yeast Infections

Diagnosis relies on clinical suspicion, microscopy, culture, antigen detection, and imaging (e.g., CT, X-ray).
Microscopy utilizes KOH and gram stains; cultures take days to weeks.
Common treatments include fluconazole and nystatin for superficial infections.

Cryptococcus Species

Cryptococcus neoformans is an encapsulated yeast that can cause mild pneumonia and severe meningitis, especially in immunocompromised patients.
Found predominantly on Vancouver Island and surrounding areas.

Pneumocystis jirovecii

A non-culturable yeast responsible for pneumonia in immunosuppressed patients, particularly those with HIV or malignancies.

Aspergillus Species

Aspergillus fumigatus is a widespread mould found in decaying vegetation.
Can cause various illnesses, especially in immunocompromised individuals.

Characteristics of Fungi

Fungi belong to one of the five kingdoms and are eukaryotic organisms.
Possess cell walls containing ergosterol; they lack chlorophyll.
Reproduce both asexually and sexually.

Yeast and Mould Morphology

Yeasts are single-celled, often elongating into chains (pseudohyphae) and reproduce via budding.
Moulds are multicellular, forming hyphae that can be septate or aseptate, leading to mycelium development and asexual spore formation.

Clinical Features of Fungal Infections

Fungal infections may present as red, scaly rashes with pustules and central clearing, known as "ringworm," "athlete's foot," or "jock itch."
Transmission occurs through contaminated fomites or skin squames, with rare person-to-person contact.

Diagnosis of Dermatophyte Infections

Involves skin scrapings, nail clippings, and hair samples, employing KOH microscopy for hyphae identification.
Cultures can take weeks, with characteristic spores aiding in speciation.

Tinea Versicolor

Caused by Malassezia furfur, a skin commensal thriving on fatty acids.
Presents as pigmented lesions and can be diagnosed via microscopy showing "spaghetti and meatballs" patterns in KOH preparations.

Invasive Fungal Infections

Two main categories: opportunistic fungi (e.g., Candida, Aspergillus) and non-opportunistic pathogens.
Infections can occur through damage, allergy, toxin ingestion, or body invasion.

Mucocutaneous Yeast Infections

Predominantly caused by Candida albicans and may affect the oral cavity, vagina, and gastrointestinal tract.
Conditions like thrush and angular cheilitis are associated with various immunocompromised states.

Skin and Nail Infections

Superficial infections often caused by Candida, presenting in damp areas or due to hygiene issues.
Dermatophytes can lead to skin, nail, and hair infections, often following minor skin trauma.

Predisposing Factors for Fungal Infections

Include minor trauma, moisture retention, and occlusive environments, which facilitate infection onset and progression.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on dimorphic fungi, specifically Histoplasma capsulatum, and systemic yeast infections such as those caused by Candida spp. This quiz will cover the associations of these infections, their presentation, and risk factors related to various medical conditions.