Chapter 21: The Fungi Flashcards by Jourdan Harkless

Yeast

Unicellular growth form of fungi
Spherical to ellipsoidal
Budding
Pseudohyphae: do not complete bud, long chain

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Hyphae

Threadlike, branching, cylindrical, tubules composed of fungal cells attached end to end
Grow by extending in length

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Molds

Also called Mycelia
Multicellular colonies composed of clumps of intertwined branching hyphae
Grow by longitudinal extension and produce spores

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Spores

Reproducing bodies of molds

Rarely seen in skin scarpings

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Dimorphic fungi

Fungi that can grow as either a yeast or mold
depends on environmental conditions and temperature
Yeast at body temp

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Saprophytes

Fungi that live in the utilize organic matter (soil, rotten vegetation) as an energy source

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cell membrane of fungi?

Bilayered, innermost layer around fungal cytoplasm
It contains sterols
Ergosterol is essential

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Cell wall of fungi

Surrounds cell membrane
Mostly carbohydrate with some protein
Potent antigens to human immune system

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Capsule of fungi

Polysaccharide coating that surrounds the cell wall
Antiphagocytic virulence factor
Indian ink stain makes visible

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What are the Extremely superficial fungus infections?

Pityriasis versicolor and Tinea nigra

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Pityriasis versicolor

Chronic superficial fungal infection which leads to hypopigmented or hyperpigmented patches on the skin
Will not tan with sun
Caused by Malessezia furfur

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Tinea nigra

Caused by Exophiala werneckii
Superficial fungal infection
Dark brown to black painless patches on soles of hands and feet

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Dermatophytoses

Cutaneous fungal infections
Live in dead, horny layer of skin, hair and nails
Secrete keratinase: digest keratin
Manifest as scaling of the skin, loss of hair, and crumbling of the nails

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What are the common dermatophytes?

Microsporum, Trichophyton, and Epidermophyton

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Tinea corporis

Ring-worm

Invades horny layer, fungi spread forming a ring with red, raised border

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Tinea cruris

Jock itch

Itchy red patches on groin and scrotum

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what are the Cutaneous fungal infection of the skin, hair and nails ?

Tinea corporis
Tinea cruris
Tinea pedis
Tinea capitis
Tinea unguium

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Tinea pedis

Athlete’s foot
Begins between toes
Causes cracking and peeling of skin
Warmth and moisture needed for growth

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Tinea capitis

Primarily in children
Grows in hair and scalp
Scaly red lesions with loss of hair
Expanding ring

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Tinea unguium

Onychomycosis

Nails thickened, discolored, and brittle

Candida albicans

Cutaneous fungal infection 
Causes Candida: 
Mouth - oral thrush
groin - diaper rash
vagina - Candida vaginitis
Cause opportunistic systemic infections

Sporothrix schenckii

Dimorphic fungi commonly found in soil and on plants Branching Hyphae
Causes: Sporotrichosis - subcutaneous nodule appears, becomes necrotic and ulcerates
Ulcer heals but new nodules pop up nearby and along lymphatic tracts
Gardeners beware!!

Phialophora and Cladosporium

Causes Chromoblastomycosis: cauliflower warts on skin
Subcutaneous infection caused by the copper-colored soil saprophytes
Puncture wound-small violet wartlike lesion–>
over months to years, more wartlike lesions arise
Looks like cauliflower

What are the three fungi that can cause systemic disease in humans? Describe the common characteristics

Histoplasma capsulatum
Blastomyces dermatidis
Coccidioides immitis

All are dimorphic fungi
grow as mycelial forms with spores @ 25C
Grow as yeast form @ 37C
In soil the grow as mycelia and release spores into the air –>inhalation

Histoplasma and Blastomyces are found where ?

endemic to the vast areas that drain into the Mississippi river HITS and BLASTS holes in Mississippi river

Coccidioides are found where?

endemic to southwestern U.S and northern Mexico

What is the second most common opportunistic infection in AIDS pts who are in Arizona?

Coccidioides

Histoplasma capsulatum, Blastomyces dermatidis, Coccidioides immitis have what 3 clinical presentations?

Asymptomatic Pneumonia: mild, can have fever, cough, chest X-ray infiltrates, granulomas with calcifications Disseminated: rarely causes meningitis, bone lytic granulomas, skin granulomas, mostly immunocompromised

How are Histoplasma capsulatum, Blastomyces dermatidis, Coccidioides immitis not similar to Tuberculosis?

No person-person transmission | Fungi with spores, NOT acid-fast bacteria

Histoplasma capsulatum

nonencapsulated Bird and bat droppings Outbreaks of pneumonia occur when cleaning chicken coops or spelunking

Blastomyces dermatitidis

Soil and rotten wood Rarest systemic fungal infection Rarely asymptomatic or mild - most chronic disseminated disease with weight loss, night sweats, lung involvement and skin ulcers

Coccidioides immitis:

commonly causes a mild pneumonia in normal persons in the southwestern US Common opportunistic infection in AIDS pts from that area

Cryptococcus neoformans

``` Widespread more common Cryptococcus to infect humans Polysaccharide encapsulated yeast Inhaled into lungs Usually asymptomatic Pigeon droppings ```

What is the major manifestation of cryptococcus neoformans?

``` Meningoencephalitis Most occur in immunocormpromised Subacute to chronic meningitis with headache, nausea, confusion, staggering gait, CN deficits Cerebral edema fatal if left untreated Lumbar puncture ```

What does Candida albicans cause in normal hosts?

Oral thrush: creamy white exudate with reddish base cover mucous membranes of the mouth Vaginitis: Vaginal itching and discharge, cottage cheese on wall Diaper rash: diapers or skin folds on adults become read and macerated

What does Candida albicans cause in immunocompromised pts

Esophagitis: Burning substernal pain worse with swallow Disseminated: Retina - multiple white fluffy patches, in bloodstream

Aspergillus fumigatus causes what three major types of diseases in humans?

Allergic Bronchopulmonary Aspergillosis Aspergilloma Invasive aspergillosis

Allergic Bronchopulmonary Aspergillosis

Spores of aspergillus inhaled Develop asthma-type reaction Type 1 hypersensitivity reaction (IgE-mediated) Bronchospasms Also a type 4 reaction with cell-mediated inflammation and lung infiltrates

Aspergilloma

Person with lung cavitation from tuberculosis or malignancies can grow an aspergillus fungal ball in the cavity

Aspergillus and other fungi produce toxins that cause liver damage. what are they called/

mycotoxins | Toxin produced by aspergillus is called aflatoxin (peanuts, grains, and rice)

Mucormycosis

Opportunistic disease caused by mucorales | Rhizopus, Rhizomucor, and Mucor

Mucorales molds are found where? Who is at risk?

Found everywhere At risk: those that develop profound acidosis, such as diabetics, the immunocompromised, burn pts, persons taking iron chelator deferoxamine

Rhinocerebral and ____ involvement is most common

pulmonary

Actinomycetes

``` bacteria acting like fungi Procaryotic organisms Frequently grow in the form of mycelia Water and soil saprophytes Acinomyces Israelli Nocardia asteroides ```

Actinomyces Israelli

Gram positive, beaded, filamentous anaerobic organisms, normal flora Causes eroding abscesses Pus is yellow granules called sulfure granules

What are the abscesses formed due to Actinomyces?

Cervicofacial actinomycosis Abdominal actinomycosis Thoracic actinomycosi Depends on what area of the body the abscess erodes

Nocardia asteroides

Weakly gram-positive Partially acid-fast beaded branching thin filaments Not normal flora Infections misdiagnosed as tuberculosis bc acid-fast staining and same disease process Inhaled and produces lung abscesses and cavitations Brain and other organs can have abscesses when erosion occurs

Who is at particular risk for infection of Nocardia ?

immunocompromised pts