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mycology
cmbm exam IV
49
Chemistry
Graduate
01/22/2010

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Term
why are fungi important to learn about even though they are less common pathogens than bacteria? what kinds of infections do they cause?
Definition
fungi are capable of very severe and rapidly fatal infections. they are opportunistic and nosocomial pathogens (4-5th leading cause of which), meaning they often cause infection in previously infected pts
Term
what is one reason fungi are increasing as opportunistic and nosocomial pathogens?
Definition
antibiotics limit bacterial infection but favor fungal infections, many immunocompromised people are living longer, due to HIV, organ transplants
Term
why are fungal infections often life threatening or fatal?
Definition
the host is usually already compromised, they are often misdiagnosed, the illness progresses rapidly, and there is a lack of safe and effective antifungals
Term
are fungi eu- or prokaryotic?
Definition
fungi are eukaryotic with a nuclear membrane around their nuclei, and have subcellular organelles such as mitochondria, ribosomes, ER, golgi, and microtubules.
Term
what is the plasma membrane of fungi called? what is it composed of? what about the cell wall?
Definition
the fungal plasma membrane or plasmalemma is composed of glycoproteins, lipids and ergosterol, (unique to fungi, mammals have cholesterol). the cell wall, which is unique to fungi is composed of chitin, (polymer of N-acetyl glucosamine), mannans, glucans, and other complex carbohydrates
Term
how do the cell types of bacteria and fungi compare? plasma membranes? cell walls? reproduction models?
Definition
fungi are eukaryotic, bacteria are prokaryotic. fungi have ergosterol in their plasma membrane, bacteria have no sterols. fungal cell walls have chitin, mannans, and glucans, bacteria have peptidoglycan, techoic acids, and LPS. fungi can reproduce via sexual and asexual spores, and budding/fission, bacteria can only replicate via binary fission
Term
what are the different kinds of fungi?
Definition
mold, (filamentous), yeast, (oval, single-celled), dimorphic fungi, (mold in nature, yeasts in tissue- due to temp), and dematiaceous fungi, (black/brown pigmented - seen more as opportunistic pathogens causing phaeohyphomycosis)
Term
how can you tell yeast cells from bacterial cocci?
Definition
yeast cells are larger
Term
wha are hyphae? what are they called with septa and without?
Definition
hyphae are filaments or tubular structures of molds. hyphae with cross walls, (septae) are septated, (aspergillus). hyphae without septae are nonseptated or cocnocytic, (zygomycetes). allows these 2 infections, which are similar to be discerned
Term
what are pseudohyphae?
Definition
hyphae-like structures formed by incomplete budding of yeast cells, that are constricted at their point of attachment, (seen in candidia albicans)
Term
what is mycelium? what are the vegetative and aerial mycelium
Definition
a mass of intertwined hyphae. vegetative mycelium absorb nutrients and aerial mycelium contain reproductive structures, asexual spores called conidia, (and their support chains: conidiophores), and sporangiospores within sporangium seen in nonseptated fungi
Term
what fungi have condiphores vs sporangium?
Definition
aspergillus has condiphores which stick out vs zygomycetes which usually has sporangium that are held closer in
Term
what are blastoconidia?
Definition
a type of conidia that is an asexual budding yeast cell. these can be seen in dimorphic fungi.
Term
what are microconidia/macroconidia?
Definition
single or multi-celled conida that are used to ID/speciate dermatophytes, (ringworm, tinea)
Term
what are arthroconidia? what function do they perform?
Definition
arthroconidia are the infectious form of coccidiodes immitis. these conidia are formed by the fragmentation of hyphae, (asexual spores).
Term
what are endospores? where are they produced?
Definition
endospores and are produced within a spherules, the asexual tissue form of coccidiodes immitis
Term
what is a fungal form producing sexual spores called?
Definition
telemorph
Term
what is a fungal form producing asexual spores called?
Definition
anamorph
Term
what are the three kinds of sexual spores?
Definition
ascospores, basidiospores and zygospores
Term
what is the classification for fungi whos sexual state is unknown?
Definition
deuteromycetes/fungi imperfecti
Term
what form are deuteromycetes with both a telomorphic and anamorphic form usually seen as, and thus referred to?
Definition
their anamorphic/asexual form
Term
are cutaneous and superficial mycoses opportunisitic infections?
Definition
no
Term
what is the most common type of fungal infection? where do they infect? are they invasive pathogens?
Definition
cutaneous mycoses caused by dermatophytes, which are all molds, causing ringworm/tinea and infections of skin/nails/hair. they are non-invasive and you don't have to be immunocompromised to be infected.
Term
what is an example of superficial mycoses?
Definition
tinea veriscolor, a fungal infection caused by malassezia furfur, (a dimorphic normal skin flora), where pigmentation changes occur
Term
what kinds of infections can be caused by candida? are they opportunisitic?
Definition
cutaneous and mucocutaneous infections. candida can be opportunistic, (causing systemic infection), or not depending on the circumstances.
Term
what fungi cause subcutaneous mycoses? how do they enter the body? are they associated with any particular thing in the environment? what kind of infection do they cause?
Definition
sporothrix schenkii, a dimorphic fungus, can enter the body through direct inoculation or a puncture wound. it is associated with rose bushes and mulch and causes subcutaneous ulcers that spread along the lymphatics draining the primary lesion.
Term
what are the 2 subgroups under systemic mycoses? what do both affect? what shapes do they take?
Definition
opportunistic and endemic mycoses. systemic infections can be caused by molds, (molds in both environment/humans), dimorphic fungi, (mold in environment/yeast in humans), and yeasts, (yeasts in environment and humans)
Term
what is characteristic of endemic mycoses? what is their morphology? are they opportunistic?
Definition
they are endemic in specific regions of the US, they are systemic mycoses that are dimorphic and not opportunistic, but more readily disseminate if the host is immunocompromised.
Term
what is characteristic of opportunistic fungi? what do their infections involve and how fatal are they?
Definition
they involve internal organs, cause systemic mycoses which can be rapidly fatal
Term
how does candida change when it becomes invasive?
Definition
candida is normal flora as yeast, but when it becomes invasive it does expres hyphae and pseudohyphae
Term
what are some examples of endemic mycoses?
Definition
blastomyces dermatitidis, coccidioides immitis, and histoplasma capsulatum
Term
what are some examples of opportunistic mycoses?
Definition
aspergillus, candida, cryptococcus neoformans, Mucor/rhizopus/zygomycetes) & pneumocystis jirovecii (pneumonia in HIV pts)
Term
what morphology do dimorphic fungi have? how are they transmitted to the pt? what severity are the infections? what is the exposure rate to people in endemic areas? how do they affect immonocompromised patients?
Definition
endemic fungi are dimorphic, they are inhaled in mold form and replicate as yeast in tissue. many cases are mild or asymptomatic. most people in endemic areas are skin test positive and immunocompromised patients are prone to disseminated disease.
Term
what area is histoplasma mycoses found in? coccioides?
Definition
histoplasma mycoses is found in the mississippi river valley and east. coccioides is found in mexico, particularly desert areas.
Term
who do opportunistic fungi cause systemic infections in?
Definition
compromised hosts, such as HIV+, transplant recipients, cancer+leukemia pts, diabetics,(metabolic acidosis - reduced pH, favor fungal growth), pts on long term antibiotics, catheterized pts, (candida, malassezia furfur), burn pts, (candida), individuals with chronic bronchitis/asthma, (aspergillus), and pts recieving corticosteroid tx
Term
what does diganosis of a fungal infection depend on? how is it confirmed?
Definition
clinical symptoms and detection of fungus in clinical specimen. this should be confirmed by cx, but pathogens are often slow growing, (days-weeks), and need some type of conidia and/or hyphae are produced, (lactopherol cotton blue is a common stain)
Term
what is a common stain used? why?
Definition
potassium hydroxide, (KOH prep), b/c its alkali treament doesn't destroy chitin+complex polysaccharides. this degrades other eukaryotic cells, allowing the fungi to stand out.
Term
what flourescent stain is used to see fungi sometimes?
Definition
calcofluor white, which can be combined with KOH
Term
what is gomori's methenamine silver?
Definition
a popular stain that turns fungi turns black/brown, easier to see
Term
how do fungi appear with gram stains? what does PAS stand for? what are some other general histological stains?
Definition
fungi usually appear gram +. PAS stands for periodic acid-schiff, and other general histological stains include giemsa, hematoxylin and cosin
Term
how useful is serology in diagnosing fungal infections? what are they more used for?
Definition
serology or (antibody detection), not as useful as with bacteria but can be used to monitor disease progress
Term
what do IgM antibodies indicate in fungal infections? 4xIgG?
Definition
IgM indicates acute infection, while 4-fold increase in IgG indicates recent infection
Term
is there antibody dectection available for endemic mycoses? what is a caveat with this process? are there ELISA setups for fungi?
Definition
yes, antibody detection of histoplasmosis, blastomycosis and coccidioidomycosis are currently available, (though you may get cross-reactivitiy between fungal antigens). there may be some ELISA setups for these types
Term
are skin tests used to diagnosis?
Definition
skin tests are not diagnostic, but they can be used to indicate past or present infection, (fungal antigens may induce cross reactivity with other fungi).
Term
what is the latex agglutination test used for?
Definition
very useful for ruling out cryptococcal meningitis (more sensitive than india ink)
Term
what tests can detect aspergillus galactomannan & candida mannan?
Definition
ELISA and latex agglutination test which detects surface membrane sugars
Term
what test can be used to look for candida?
Definition
tests for D-arabinitol in serum, which is associated w/disseminated candidiasis
Term
what would tests for D-mannitol in bronchoalveolar lavage fluid specimens detect?
Definition
pulmonary aspergillosis
Term
what does the limulus lysate assay for beta-1,3-glucan tell you?
Definition
if positive, indicates presence of fungus, but doesn’t ID genera. it is useful for patients with invasive candidiasis and aspergillosis
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