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64 Cards in this Set
- Front
- Back
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Component of fungi cell wall that increases rigidity:
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chitin
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predominant sterol in fungi:
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ergosterol
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how do fungi reproduce?
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sexually: spores
asexually: budding |
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general types of diseases are caused by fungi:
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hypersensitivity diseases
superficial, cutaneous and subcutaneous mycoses systemic mycoses opportunistic mycoses |
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how you differentiate b/w hyphae and pseudohyphae:
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pseudohyphae: "pinched off", sausage-like
hyphae: truly septate |
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a network of hyphae:
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mycelium
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spores for mold that result when mycelium break off:
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arthroconidia
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two types of spores that help identify a mold:
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1. sporangiospores (a zygomycete)
2. conidia (an aspergillus species) |
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how to differentiate a sporangiospore from a conidia:
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sporangiospore: infrequent septum; location of rhizoids
conidia: frequently septate |
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the 2 forms that fungi may have and the temperatures they grow at:
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yeast - 35 degrees (Celcius)
mold - 25 degrees |
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What are the dimorphic fungi?
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4 most important dimorphic fungi:
Histoplasma capsulatum Blastomyces dermatitidis Coccidiodes immitis Sporothrix schenckii Paracoccidioides brasiensis Penicillium marneffei |
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3 ways that fungi are spread:
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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 |
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What are 4 general ways that fungi cause disease?
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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 |
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How do Histoplasma yeast avoid phagocytosis and thus cause disease?
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they multiple in macrophages
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How does Cryptococcus avoid phagocytosis?
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it has a capsule
(Crypt --> capsule) |
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What is the most common fungal infection?
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Candidiasis
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Where is Candida usually found?
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found in normal flora of respiratory, GI + GU tract
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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** |
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D/Dx: germ tube (+), most common Candida
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C. albicans
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most common Candida from oral or fecal specimens of HIV-positive pts?
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C. dubliniensis
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only Candida without pseudohyphae?
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C. glabrata
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C. glabrata:
associated with what clinical problems? resistant to what drug? |
assoc w/ UTIs (occasional vaginitis)*
resistant to fluconazol* |
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Candida that is resistant to anti-fungals?
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C. krusi
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Candida associated w/ endocarditis?*
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C. parapsilosis*
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Candida in pts w/ lymphoreticular malignancies?
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C. tropicalis
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Candida adheres to mucosal cells, what lytic enzymes does it use?
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phospholipases and proteases
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Species of Candida that uses both types of lytic enzymes?
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C. albicans uses proteases and phospholipases
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Action of Candida's proteases?
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proteases are lytic for keratin --> invasion of epithelial surfaces
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How does Candida activate the alternative complement pathway?
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cell wall mannan is the activator
(i.e. it is antigenic and leads to phagocytosis and killing of Candida) |
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What form of candidiasis is associated with defects in cell-mediated immunity?
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mucocutaneous
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What keeps an AIDS pt from having a systemic infection from esophageal candidiasis?
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neutropenic pts get the systemic infection
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4 risk factors for Candida infections?
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1. antibiotic therapy
2. corticosteroid use 3. decreased T-cell function 4. diabetes |
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clinical manifestations of Candida?
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skin and nail infections
mucocutaneous (ex: oral thrush) vulvovaginal infection chronic mucocutaneous endophthalmitis esophagitis systemic |
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Who gets mucocutaneous candidiasis?
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kids <3 yo w/ cellular immunity or endocrine gland defects
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how can systemic Candida infections manifest?
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fungemia
endocarditis pulmonary infection UTI meningitis (very rare) endophthalmitis |
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How do you diagnose Candida albicans*
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1. gram stain
2. calcoflour white stain* (attaches to chitlin; test yeast for germ tube* production 3. biochemical tests (no serology) |
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How does Candida albicans appear on gram stain?**
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**clusters of round blastoconidia along the hyphae, especially at the septa
(also see pseudohyphae and true hyphae)** |
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What does C. albicans look like on dextrose agar?
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white to cream-colored, pasty, smooth colonies
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What 2 Candida species produce a typical asexual spore and what is this spore called?**
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**C. albicans and C. dubliniensis produce a chlamydospore**
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**What are germ tubes? What Candida species produce them?**
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germ tubes are beginning of true hyphae
C. albicans and C. dubliniensis produce them and this is useful for lab diagnosis! |
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characteristics of aspergillosis?
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rapidly-growing mold (blue-green colonies)
found in air, soil, construction site dust dichotomous branching (45 degree angles) septate hyphae* |
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D/Dx: rapidly-growing mold (blue-green colonies); found in air, soil, construction site dust; dichotomous branching (45 degree angles); septate hyphae*
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Aspergillosis
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how do you ID aspergillus?
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color and structures
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clinical manifestations of aspergillus? (4)
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1. allergic aspergillus
2. fungus ball in pre-existing cavity (TB, emphysema) 3. invasive aspergillosis 4.dissemination infection |
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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) |
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Characteristics of Zygomycosis?
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abundant in environment
opportunisitic infection |
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Host risk factors for Zygomycosis?
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1. metabolic acidosis
2. diabetes mellitus 3. severe leukopenia 4. immunosuppressed |
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4 organisms that cause zygomycosis?
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1. Rhizopus (most common)
2. Rhizomucor 3. Absidia 4. Mucor (least common) |
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Zygomycosis: clinical syndromes?
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1. rhinocerebral zygomycosis
2. mucormycosis (aka zygomycosis) 3. lung, GI tract, subQ tissue 4. disseminated dz |
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What is mucormycosis (aka zygomycosis)?
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periorbital fungal infection usually in immunocompromised pts that spreads to brain
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**What does a tissue specimen of mucormycosis look like?**
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hyaline, rarely septate, broad and irregularly branched hyphae, look ribbon-like on silver stain, 90 degree branching
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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)
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What is Dermatophytosis?
What group of fungi cause it? |
=fungal infection of keratinized tissues (skin, hair, nails)
due to the dermatophytes |
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How is dermatophytosis transmitted?
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close personal contact
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How do dermatophytes grow on culture?
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slow-growing at 25 degrees
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What is "ringworm" and why is it called this?
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"ringworm" = dermatophytosis
named this due to irregular inflammatory border of the skin lesion |
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**What are the 3 genera of Dermatophytosis?**
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Epidemophyton
Microsporum Trichophyton |
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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 |
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3 species that most commonly cause Tinea pedis?
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T. rubrum, T. mentagrophytes, E. floccosum
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What is Tinea capitis?
What's the predominant cause in U.S.? |
=dermatophytosis of scalp due to hair invasion
T. tonsurans |
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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 |
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What is Latin name for "jock itch"?
Causes? |
Tinea cruris
due to T. rubrum, E. floccusum |
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How do dermatophytic infections spread?
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they spread laterally, not deeper
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**lab diagnosis of dermatophytosis?**
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**direct exam of leading edge of skin lesion by KOH or calcoflour**
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