Medical Mycology Flashcards by Eldren Joi Malsi

A specialized discipline in the field of biology concerned with the study of fungi, including their taxonomy, environmental impact, and genetic and biochemical properties.

Mycology

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Major factors responsible for the increase in the number of fungal infections

Growing number of immunocompromised people

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Major predisposing factors for fungal infections

Immunocompromised host
Complex surgical procedures
Antibacterial therapy

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Living on dead or decayed organic matter in nature

Saprophytic

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Humans become accidental hosts for fungi by

Inhaling of spores
Direct contact with spores
Introduction of fungal elements into tissue by trauma.

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Colony appearance of yeasts

Moist, creamy, opaque or pasty colonies

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Colony appearance of molds

Fluffy, cottony, woolly, or powdery colonies

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Fungal pathogens that exhibit either a yeast (or yeast-like) phase, and filamentous forms

Dimorphic fungi

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When dimorphism is temperature dependent, the fungi are designated

Thermally dimorphic

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Ideal temperature for molds

25° to 30°C

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Ideal temperature for yeasts

35° to 37°C

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The medically important dimorphic fungi

Histoplasma capsulatum
Blastomyces dermatitidis
C. immitis
Paracoccidioides brasiliensis
Sporothrix schenckii
Penicillium marneffei

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Fungi that have more than one independent form or spore stage in their life cycle

Polymorphic fungi

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Polymorphic fungi groups are temperature dependent. True or false?

False

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General characteristics of fungi

Eukaryotic
Thallophytes
Chitin in the cell wall
Ergosterol in the cell membrane
Reproduction by means of spores, produced asexually or sexually
Lack of chlorophyll
Lack of susceptibility to antibacterial antibiotics
Saprophytic nature

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Have true nuclei and are heterotrophic members of the plant family

Thallophytes

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Sexual reproduction of zygomycota

Zygospores

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Asexual reproduction of zygomycota

Sporangiospores

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Asexual reproduction of zygomycota

Sporangiospores

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Fungi that produce hyaline sparsely septate hyphae

Zygomycota

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Clinically important genera of phylum zygomycota

Rhizopus
Mucor
Rhizomucor
Lichtheimia (Absidia)
Cunninghamella

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Asexual reproduction of ascomycota

Conidia

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Known as asexual spores

Conidia

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Sexual reproduction of ascomycota

Ascospores

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Sexual form of fungi

Teleomorph

Asexual form of fungi

Anamorph

Fungi that have different asexual forms of the same fungus are called

Synanomorphs

Anamorphic forms of Pseudallescheria boydii

Scedosporium apiospermum Graphium

Species with graphium anamorph

Microsporum spp. Trichophyton spp. Pseudallescheria boydii

Teleomorphic form of H. capsulatum

Ajellomyces

Teleomorphic form of Aspergillus

Eurotium

Sexual reproduction of basidiomycota

Basidiospores

Specialized structure where basidiospores are formed

Basidia

The teleomorphic form of C. neoformans

Filobasidiella neoformans

Asexual reproduction of deuteromycota

Conidia

Sexual reproduction of deuteromycota

Lacks sexual reproductive cycle

Fungal infections that involve the hair, skin, or nails without direct invasion of the deeper tissue.

Superficial or cutaneous mycoses

Agents of ringworm, athlete’s foot

Dermatophytes

Examples of subcutaneous infections

Sporothricosis Mycetoma Chromoblastomycosis Phaeohyphomycotic cysts

Agents of systemic fungal infections

Blastomyces Coccidioides Histoplasma Paracoccidioides P. marneffei

Primary organ involved in systemic mycoses

Lungs

Primary mode of acquisition of systemic mycoses

Inhalation

Agents of superficial or cutaneous fungal infections

Dermatophytes Tinea nigra Tinea versicolor Piedra

Infections that occur primarily in patients with some type of compromise of the immune system.

Opportunistic mycoses

Commonly encountered infections caused by opportunistic mycoses

Aspergillosis Candidiasis Cryptococcosis Zygomycosis

Fungal infections involved in deeper skin layers, including muscle, connective tissue, and bone

Subcutaneous mycoses

Fungal infections that disseminate and involve any organ system

Systemic mycoses

Fungi that produce brown-pigmented structures

Dematiaceous fungi Phaeoid hyphae

Hyphae with crosswalls

Septate hyphae

Hyphae that is continuous without crosswalls

Aseptate hyphae or Sparsely septate / Coenocytic

Nonpigmented hyphae is considered

Moniliaceous / Hyaline hyphae

Color of dematiaceous fungi

Pale to dark brown or almost black

Stain used to ditermine hyphal pigmentation in the tissue

Masson-Fontana stain

In Masson-Fontana stain 1. Phaeoid hyphae stains ____ 2. Hyaline hyphae stains ____

Black Pink to red

Science devoted to the study of fungi and their relationship to human disease

Medical Mycology

Fungal agents include:

True pathogens Opportunistic pathogens

Fungi that lack sexual reproduction; they are represented only by mitotic or asexual reproductive state

Imperfect fungi

Fungi that are capable of fungal reproduction = TELEOMORPH

Perfect fungi

Hyphal or mycelial colony of growth

Mold

Unicellular, spherical to ellipsoid (3-5um) fungal cells; reproduce by budding

Yeast

Oxygen requirement of molds

Almost all molds are aerobic

Oxygen requirement of yeasts

Most yeasts are facultative anaerobes

General characteristics of fungi: GMRC

Most are more resistant to osmotic pressure than bacteria Can grow on very low moisture content Require less nitrogen than bacteria Often capable of metabolizing complex carbohydrates, such as lignin

Identification of yeasts is based primarily on

Biochemical testing

How does yeasts divide?

Few divide by BINARY FISSION but most reproduce asexually by BUDDING

Identification of molds is based on

Growth rate Macroscopic and microscopic appearance

Tubular, branching filaments (2–10 m in width) of fungal cells, mold form of growth

Hyphae

Microscopic units of fungi

Hyphae

Cross-walls that divide hyphae

Septa

Swollen, branching tips that resemble moose antlers ,with lateral and terminal branching

Antler hyphae

Contain enlarged, club-shaped areas resembling a tennis racquet

Raquet hyphae

Tightly coiled showing corkscrew-like turns

Spiral hyphae

Example of antler hyphae

Trichophyton shoenleinii

Example of raquet hyphae

Epidermophytoc floccosum

Example of spiral hyphae

Trichophyton mentagrophytes

Mass of intertwining structure composed of hyphae

Mycelium

Portion of mycelium that grows in or on a substrate and absorbs water and nutrients; anchor the colony

VEGETATIVE PORTION OR THALLUS

Portion of mycelium that contains fruiting bodies that produce the conidia and spores; extends above the agar surface

REPRODUCTIVE PORTION OR AERIAL

Requires formation of special structures so that fertilization or nuclear fission can occur

SEXUAL REPRODUCTION

Do not exhibit a sexual phase; spores are produced asexually from mycelium

ASEXUAL REPRODUCTION

Fungi that have different asexual forms of the same fungus

SYNANOMORPHS

Types of sexual spores

Ascospores Basidiospores Zygospores Oospores

Types of asexual spores

Arthroconidia Blastoconidia Chlamydoconidia Sporangiospores

Contained in a saclike structure called ASCUS

Ascospores

Following meiosis, how many meiospores form within an ascus

4-8

Contained in a club-shaped BASIDIUM

Basidiospores

Following meiosis, how many meiospores usually form on the surface of a basidium

Rough-walled spores produced by the fusion of two identical cells arising from the same hypha

Zygospores

Formed by heterogenous fertilization. Involve the fusion of cells from separate, nonidentical hyphae

Oospores

Conidia that result from the simple fragmentation of hyphal cells

Arthroconidia

Simplest type of sporulation

Arthroconidia

Empty spaces that appear between each arthrospores in alternate arrangement

Disjunctor cells

Conidial formation through a budding process

Blastoconidia

Large, thick-walled, usually spherical conidia produced by “rounding-up” and enlargement of the terminal hyphal cells

Chlamydoconidia

Chlamydoconidia formed at the hyphal tip

Terminal

Chlamydoconidia formed at the hyphal sides

Sessile

Chlamydoconidia formed within the hyphal strand

Intercalary

Mitotic spores produced within an enclosed sporangium, often supported by one sporangiophore

Sporangiospores

Asexual spores (mitospores) produced either singly or multiply in long chains or clusters by specialized vegetative hyphae = Conidiophores

Conidia

Flask-shaped secondary segments which produces the conidia = Phialoconidia

Phialides

Ringed structures that produce Annelloconidia

Annellides

Formation of conidia

CONIDIOGENESIS

Conidiogenesis where parent cell enlarges, a septum forms and the enlarge portion splits off to form a daughter cell

Blastic Conidiogenesis

Conidiogenesis where septum forms first and new growth beyond the septum becomes daughter cell

Thallic Conidiogenesis

Small, unicellular with a round, elliptical, or pyriform shape

Microconidia

Large, usually multiseptate, and club oval or spindle shaped; thick or thin walled; spiny or smooth surface

Macroconidia

Term for spiny Macroconidia

Echinulate

Conidia that are produced by a "vase-shaped"

Phialoconidia

Chain of conidia was produced by an

Annellide

Ubiquitous in nature and produce true septate hyphae All exhibit a sexual form (teleomorph) but also exist in an asexual form (anamorph)

Ascomycota

Generally plant pathogens or environmental organisms that rarely cause disease in humans

Basidiomycota

Not a true phylogenetic group but rather an artificial class

Deuteromycota

Deuteromycota is also known as

FUNGI IMPERFECTI

Characteristics of superficial / cutaneous mycoses

Confined to the outermost layer of skin or hair All infect keratinized tissues

Causative agent of oral thrush

Candida albicans

Function of spores in fungi

Reproduction

Causative agent of gas gangrene

Clostridium perfringes

Antler hyphae is also known as

Favic chandelier

Trichophyton spp. affects

Hair Skin Nails

Epidermophyton affects

Skin Nails

Microsporum spp. affects

Hair Skin

Causative agent of Pytiriasis versicolor

Malassezia furfur

Causative agent of rose gardener's disease

Sporothrix schenckii

Causative agent of fungal meningitis

Cryptococcus neoformans

Unique structure in fungi

Chitin in the cell wall