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64 Cards in this Set

  • Front
  • Back
Component of fungi cell wall that increases rigidity:
predominant sterol in fungi:
how do fungi reproduce?
sexually: spores

asexually: budding
general types of diseases are caused by fungi:
hypersensitivity diseases
superficial, cutaneous and subcutaneous mycoses
systemic mycoses
opportunistic mycoses
how you differentiate b/w hyphae and pseudohyphae:
pseudohyphae: "pinched off", sausage-like

hyphae: truly septate
a network of hyphae:
spores for mold that result when mycelium break off:
two types of spores that help identify a mold:
1. sporangiospores (a zygomycete)
2. conidia (an aspergillus species)
how to differentiate a sporangiospore from a conidia:
sporangiospore: infrequent septum; location of rhizoids

conidia: frequently septate
the 2 forms that fungi may have and the temperatures they grow at:
yeast - 35 degrees (Celcius)

mold - 25 degrees
What are the dimorphic fungi?
4 most important dimorphic fungi:
Histoplasma capsulatum
Blastomyces dermatitidis
Coccidiodes immitis
Sporothrix schenckii

Paracoccidioides brasiensis
Penicillium marneffei
3 ways that fungi are spread:
1. person-to-person: Athlete's foot
2. environ contacts: inhalation of spores, traumatic inocculation
3. contact w/ animals: inhalation of bird droppings, touch infected skin or hair of dogs
What are 4 general ways that fungi cause disease?
1. adherence
2. invasion of natural barriers
3. avoid phagocytosis
4. host immunity - humoral immunity is not effective, thus cellular immunity is required to eradicate infection
How do Histoplasma yeast avoid phagocytosis and thus cause disease?
they multiple in macrophages
How does Cryptococcus avoid phagocytosis?
it has a capsule

(Crypt --> capsule)
What is the most common fungal infection?
Where is Candida usually found?
found in normal flora of respiratory, GI + GU tract
What does Candida look like when found:
in body fluids?
in tissues?
on culture?
fluids: oval budding yeasts

tissues: yeast w/ pseudohyphae

on culture: Candida resembles bacteria**
D/Dx: germ tube (+), most common Candida
C. albicans
most common Candida from oral or fecal specimens of HIV-positive pts?
C. dubliniensis
only Candida without pseudohyphae?
C. glabrata
C. glabrata:
associated with what clinical problems?

resistant to what drug?
assoc w/ UTIs (occasional vaginitis)*

resistant to fluconazol*
Candida that is resistant to anti-fungals?
C. krusi
Candida associated w/ endocarditis?*
C. parapsilosis*
Candida in pts w/ lymphoreticular malignancies?
C. tropicalis
Candida adheres to mucosal cells, what lytic enzymes does it use?
phospholipases and proteases
Species of Candida that uses both types of lytic enzymes?
C. albicans uses proteases and phospholipases
Action of Candida's proteases?
proteases are lytic for keratin --> invasion of epithelial surfaces
How does Candida activate the alternative complement pathway?
cell wall mannan is the activator
(i.e. it is antigenic and leads to phagocytosis and killing of Candida)
What form of candidiasis is associated with defects in cell-mediated immunity?
What keeps an AIDS pt from having a systemic infection from esophageal candidiasis?
neutropenic pts get the systemic infection
4 risk factors for Candida infections?
1. antibiotic therapy
2. corticosteroid use
3. decreased T-cell function
4. diabetes
clinical manifestations of Candida?
skin and nail infections
mucocutaneous (ex: oral thrush)
vulvovaginal infection
chronic mucocutaneous
Who gets mucocutaneous candidiasis?
kids <3 yo w/ cellular immunity or endocrine gland defects
how can systemic Candida infections manifest?
pulmonary infection
meningitis (very rare)
How do you diagnose Candida albicans*
1. gram stain
2. calcoflour white stain* (attaches to chitlin; test yeast for germ tube* production
3. biochemical tests (no serology)
How does Candida albicans appear on gram stain?**
**clusters of round blastoconidia along the hyphae, especially at the septa
(also see pseudohyphae and true hyphae)**
What does C. albicans look like on dextrose agar?
white to cream-colored, pasty, smooth colonies
What 2 Candida species produce a typical asexual spore and what is this spore called?**
**C. albicans and C. dubliniensis produce a chlamydospore**
**What are germ tubes? What Candida species produce them?**
germ tubes are beginning of true hyphae

C. albicans and C. dubliniensis produce them and this is useful for lab diagnosis!
characteristics of aspergillosis?
rapidly-growing mold (blue-green colonies)
found in air, soil, construction site dust
dichotomous branching (45 degree angles)
septate hyphae*
D/Dx: rapidly-growing mold (blue-green colonies); found in air, soil, construction site dust; dichotomous branching (45 degree angles); septate hyphae*
how do you ID aspergillus?
color and structures
clinical manifestations of aspergillus? (4)
1. allergic aspergillus
2. fungus ball in pre-existing cavity (TB, emphysema)
3. invasive aspergillosis
4.dissemination infection
how do you diagnose aspergillus in the lab?

what must you differentiate it from?
rapid growth on Sabourad's agar
must culture to ID and give therapy

differentiate from zygomycetes (non-septate, broad hyphae, assoc w/ diabetics and immunocompromised)
Characteristics of Zygomycosis?
abundant in environment
opportunisitic infection
Host risk factors for Zygomycosis?
1. metabolic acidosis
2. diabetes mellitus
3. severe leukopenia
4. immunosuppressed
4 organisms that cause zygomycosis?
1. Rhizopus (most common)
2. Rhizomucor
3. Absidia
4. Mucor (least common)
Zygomycosis: clinical syndromes?
1. rhinocerebral zygomycosis
2. mucormycosis (aka zygomycosis)
3. lung, GI tract, subQ tissue
4. disseminated dz
What is mucormycosis (aka zygomycosis)?
periorbital fungal infection usually in immunocompromised pts that spreads to brain
**What does a tissue specimen of mucormycosis look like?**
hyaline, rarely septate, broad and irregularly branched hyphae, look ribbon-like on silver stain, 90 degree branching
D/Dx: hyaline, rarely septate, broad and irregularly branched hyphae, look ribbon-like on silver stain, 90 degree branching

culture shows sporangia, growth is woolly white to grey
Zygomycosis (mucormycosis)
What is Dermatophytosis?

What group of fungi cause it?
=fungal infection of keratinized tissues (skin, hair, nails)

due to the dermatophytes
How is dermatophytosis transmitted?
close personal contact
How do dermatophytes grow on culture?
slow-growing at 25 degrees
What is "ringworm" and why is it called this?
"ringworm" = dermatophytosis

named this due to irregular inflammatory border of the skin lesion
**What are the 3 genera of Dermatophytosis?**
What is the most common dermatophyte infection?

What happens when it spreads?
Tinea pedis (Athlete's foot)

may spread to sole, arch, and heel causing hyperkeratosis and scaling
3 species that most commonly cause Tinea pedis?
T. rubrum, T. mentagrophytes, E. floccosum
What is Tinea capitis?

What's the predominant cause in U.S.?
=dermatophytosis of scalp due to hair invasion

T. tonsurans
What is Tinea corporis?

What do the lesions look like?
=dermatophytosis of glabrous (hairless) skin

lesions are variable in size, annular, sharp margins, w/ raised, red, serpiginous border
What is Latin name for "jock itch"?

Tinea cruris

due to T. rubrum, E. floccusum
How do dermatophytic infections spread?
they spread laterally, not deeper
**lab diagnosis of dermatophytosis?**
**direct exam of leading edge of skin lesion by KOH or calcoflour**