Mycology: Fungal Classification and Antifungals

Questions and Answers

What is mycology?

Study of fungi (yeasts and molds)

Eukaryotic organisms are distinguished by which of the following?

Rigid cell wall composed of chitin and glucan

Cell membrane that contains ergosterol

Both A and B (correct)

None of the above

Fungi are considered as either:

Saprobes

Symbionts

Commensals

All of the above (correct)

How are fungi classified taxonomically?

Morphology and mode of spore production Signup and view all the answers

What are yeasts?

Single cells that reproduce by asexual budding or by fission Signup and view all the answers

What describes molds?

Multicellular organisms consisting of long tubular filaments called hyphae Signup and view all the answers

When growing on solid surfaces, molds produce what type of hyphae?

Vegetative hyphae and aerial hyphae Signup and view all the answers

Many fungi of medical importance are dimorphic.

True Signup and view all the answers

How do most fungi perform respiration?

Most fungi exhibit aerobic respiration, some are facultatively anaerobic, and others are strict anaerobes. Signup and view all the answers

Fungi are ______ compared to most bacteria.

slow growing Signup and view all the answers

Fungi reproduce by the formation of what?

Spores which may be sexual or asexual Signup and view all the answers

The form of fungus producing sexual spores is the __ and the form producing asexual spores is the _

teleomorph, anamorph Signup and view all the answers

The anamorphic (asexual) state is isolated from what?

Clinical specimens Signup and view all the answers

Asexual spores consist of which types?

Both A and B Signup and view all the answers

What are conidia?

Spores born naked on specialized structures Signup and view all the answers

What are sporangiospores?

Spores produced in a containing structure called a sporangium Signup and view all the answers

What are superficial mycoses?

Limited to very superficial surfaces of skin and hair Signup and view all the answers

What do cutaneous mycoses affect?

The keratinized layer of the skin, hair, and nails Signup and view all the answers

What are subcutaneous mycoses?

Involve deeper layers of skin, cornea, muscle, and connective tissue Signup and view all the answers

What are endemic mycoses?

Caused by classic dimorphic fungal pathogens Signup and view all the answers

What are opportunistic mycoses?

Normally found as human commensals or in the environment Signup and view all the answers

All primary systemic fungal pathogens are agents of respiratory infections.

True Signup and view all the answers

What are the phases of fungal disease?

Saprobic phase and parasitic phase Signup and view all the answers

Study Notes

Mycology Overview

Mycology is the study of fungi, which includes yeasts and molds.

Eukaryotic Characteristics

Fungi are eukaryotic organisms with a rigid cell wall made of chitin and glucan.
The cell membrane contains ergosterol, unlike bacteria that contain cholesterol.

Types of Fungi Based on Habitat

Saprobes: feed on dead or decaying matter.
Symbionts: live in mutual benefit relationships.
Commensals: one organism benefits while the other is unaffected.
Parasites: exploit hosts for benefit, potentially harming them (pathogens).

Taxonomic Classification

Fungi are classified based on morphology and mode of spore production.

Yeast Characteristics

Yeasts are unicellular, reproduce asexually through budding or fission.
Daughter cells may elongate into pseudohyphae, and colonies appear round and mucoid on agar.

Mold Characteristics

Molds are multicellular with hyphae that elongate apically.
Hyphae can form mycelium and colonies that are described as filamentous or hairy.

Molds on Culture Media

When growing on agar, molds produce vegetative hyphae and aerial hyphae.

Dimorphic Fungi

Many medically significant fungi exist in both yeast and mold forms.

Fungal Respiration

Most fungi practice aerobic respiration; some can also perform fermentation or are anaerobic.

Growth Rate

Fungi grow more slowly than most bacteria.

Fungal Reproduction

Fungi reproduce via spores, which can be sexual or asexual.

Fungal Morphological Forms

Teleomorph refers to the sexual spore-producing form, while anamorph refers to the asexual spore-producing form.

Clinical Specimen Isolation

Asexual states (anamorphic) of fungi are isolated from clinical specimens.

Types of Asexual Spores

Asexual spores include sporangiospores (contained in a sporangium) and conidia (naked, produced on special structures).

Superficial Mycoses

Affect the outer skin and hair, with non-destructive cosmetic implications.

Cutaneous Mycoses

Involve the keratinized layers of skin, hair, and nails, may elicit host immune responses, leading to symptoms like itching or scaling.

Subcutaneous Mycoses

Impact deeper skin layers, cornea, muscle, and connective tissue, often introduced through trauma, can cause abscesses and nonhealing ulcers.

Endemic Mycoses

Caused by dimorphic pathogens, true pathogens that primarily affect healthy individuals.
Notable examples: Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides spp., Paracoccidioides brasiliensis.
Exhibit thermal dimorphism—yeast form at 37°C and mold form at 25°C.

Opportunistic Mycoses

Typically human commensals or environmental fungi with limited virulence, causing infections primarily in immunocompromised individuals.
Major causative agents include Candida spp., Cryptococcus neoformans, Aspergillus spp., and Pneumocystis jirovecii.

Primary Pathogens and Respiratory Infections

All systemic fungal pathogens are agents of respiratory infections.

Fungal Disease Phases

Saprobic phase: characterized by filamentous septate hyphae in soil producing airborne infectious cells.
Parasitic phase: able to grow at 37°C and reproduce, typically within a host.

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Description

Test your knowledge on mycology with this quiz focused on fungal classification, diagnosis, and antifungal agents. Dive into the details of eukaryotic organisms and their characteristics, as well as the importance of mycology in understanding fungi.