Term
| What are fungal infections called? |
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Definition
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Term
| What are the two major endogenous type infections? |
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Definition
-Candidiasis and malassezia sp. (causes tinea versicolor)
-Basically all other infections are exogenous |
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Term
| What does the fungal envelope look like? What gives it's pm strength? |
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Definition
-It has a cell wall composed of chitin and a few others (later)
-The pm has sterols, namely ***ergosterol and *zymosterol |
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Term
| What composes the cell wall and what is it made of? Which is the one involved in resistance, and resistance of what? |
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Definition
-*Chitin; N-acetlyglucosamines in beta-1,4 bonds
-*Glucan; Glucose in beta-1,6 bonds
-*Mannan; mannoses in alpha-1,6 bonds
-Cellulose and chitosan are the other two, and make the cell wall *resistant to acid/base reactions
-This is important because we can use dilute KOH preps to "clear" samples of all other cells (only fungi cells live)
-Allows us to look at specimens without culturing |
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Term
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Definition
-It is a fungal infection caused by the organism **Blastomyces dermatitidis
-Can cause some pretty bad skin lesions
-Often presents early as the flu-like illness which can develop into chronic pulmonary infection, and later a widespread disseminated infection (skin, bones, etc.) |
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Term
| What is the gram status, tropic status, aerobic status, division speed, and cutaneous food used by fungi? |
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Definition
-They are heterotropic, gram+, not acid-fast, aerobic or faculatative anaerobes (never strict anaerobes) and divide much slower than bac (hours)
-Cutaneous fungi metabolize keratin |
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Term
| What are the two basic morphologic forms of fungi? |
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Definition
-Yeast; unicellular
-Hyphae; branching, threadlike filaments |
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Term
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Definition
| -By blastoconidia (blastospore) formation; *budding |
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Term
| What do we call a whole bunch of hyphae? |
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Definition
-A mycelium
-It appears as mold |
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Term
| What are the two kinds of hyphae? What about their classification based on position? What can the second position do? |
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Definition
-Can be *septate (separated by septa)
-Or can be aseptate, which we call *coenocytic (hollow and multinucleated)
-Also, they can be vegetative (on or in the medium) or aerial hyphae
-Aerial hyphae often produce **conidia (general term for spore) which are easily *airborne
-conidia is greek derivative of "dust" |
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Term
| What morphology do Candida albicans cells assume? What is the method that this morphology uses to reproduce? |
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Definition
-Can be yeast-like, or can assume a *pseudohyphal morphology where the cells are linked like sausages
-This type of morphology is accomplished by an exaggerated form of budding (buds remain attached)
-They often produce *chlamydospores (thick walled spores [conidia] at end or at junction)
-Remember, this is one of the two opportunists |
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Term
| What is the process of budding? What type of reproduction uses this method? |
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Definition
-The process begins with intentional, restricted autolytic damage to a small portion of the cell wall
-Then the pm bubbles out, the nucleus divides in the mother cell, half goes to the bud, and then it separates off
-**Blastospores are formed by budding |
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Term
| What are the four phyla of fungi? Which is the important one? |
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Definition
-Ascomycetes
-Basidiomycetes
-**Deuteromycetes (Fungi imperfecti)
-Zygomycetes
-The first two are big ones, like mushrooms, and the last one is more molds and such
-The medically important phylum is **deuteromycota, or **imperfect fungi, which do not produce sexually (hence the name imperfect; as they cannot be classified among the other phyla) |
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Term
| What is the medium on which we grow fungi? What are its special characteristics? What can we add to it to increase selectivity? What does the temp matter? |
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Definition
-*Sabouraud's agar has a lower pH of 5.0 to discourage bacterial growth while encouraging mycotic growth
-We can add in cyclohexamide and choramphenicol which inhibit nonpathogenic fungi (antibiotics)
-We can incubate at 25°C or 37°C with the warmer temp producing yeast, and colder producing mold (in dimorphic fungal agents) |
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Term
| What are the two major groups of conidia? |
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Definition
-Conidia, or spores, can be;
-Thallic conidia; a cell becomes the spore
-Blastic conidia; bud off cell |
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Term
| Give the three subclasses of thallic conidia? |
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Definition
1. Aleuriospore;
2. Arthrospore
3. Chlamydospore |
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Term
| What identifies aleuriospores? What are the two types? What infectious fungi type can we identify by this spore type? |
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Definition
-They are spores that grow out on short lateral branches (*microconidia) or directly from the hyphae (*macroconidia)
-Look almost like pinecones/christmas bulbs on a tree, except for the macroconidia, which is an enlarged end
-The *dermatophytes (skin disease fungi), can be identified by the aleuriospores they produce |
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Term
| What is the method of arthrospore generation? Give an important example? |
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Definition
-Hyphae form a double septum and break apart
-*Coccidiodes immitis causes *Valley fever and uses this method of asexual reproduction |
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Term
| What characterizes chlamydospres? What uses them? |
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Definition
-They are thick-walled spores that form at the end of hyphae or between segments
-**Candida albicans** uses these |
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Term
| Give the three kinds of blastic conidia? |
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Definition
3. Blastospores
4. Conidiospores
5. Sporangiospores |
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Term
| What is the method of blastospore generation? Give two fungi that use this method? |
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Definition
-They are formed by **budding yeast
-Candida and Blastomyces use blastopores |
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Term
| What is the method of conidiospore generation? Give two fungi that use this method? |
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Definition
-Occur singly or at the end of specialized structures called **conidiosphores (look almost like a painters brush)
-*Aspergillus and *penicillum are two important ones |
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Term
| What is the method of sporangiospore generation? Give a fungi that use this method? |
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Definition
-From formation of a saclike *sporangia at the end of specialized hyphae called *sporangiophores
-Look like dandelions after they go to seed (but solid ball)
-*Zygomycetes use this method (they are one of the four phylums of fungi)
-*Rhizopus sp. (type of zygomycota) can sometimes be infections (black bread mold is a rhizopus) |
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Term
| What are the three methods of asexual reproduction? |
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Definition
-Budding; one cell becomes two (blastopores use this)
-Fragmentation; breaks off and grows elsewhere
-Sporulation; the six types of conidia just reviewed |
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Term
| How does parasexual reproduction occur? |
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Definition
| -Basically two cells combine, mix up their DNA in newly created strands, and then divide into four daughters (two with the new recombined DNA) |
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Term
| What are the medically relevant sexual spores called? Give the organization? |
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Definition
-*Ascospores from **aspergillus nidulans
-The ascopores are inclosed in an *ascus, and many asci are enclosed in a large *cleistothecium
-Note; most medically important fungi cannot reproduce sexually |
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Term
| Give five commonly used diagnostic lab procedures for fungi? Give relevant info for each? |
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Definition
1. KOH; wipes out other cells, but not fungi
-Good for skin scrapings or pus
-No need to culture
2. Wood's lamp; UV light for looking at skin fungi
3. India Ink preperation; for encapsulated fungi
-Specifically used for *CSF suspected of containing Cryptococcus neoformans (fungal meningitis)
-The capsule will appear large and clear on the dark background in light microscopy
4. Periodic Acid-Schiff Stain (PAS); stains red
-Used often for tissue and sputum
5. Lactophenol cotten blue, we mount; for cultured cells |
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Term
| List the 10 antifungal antibiotics? |
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Definition
1. Amphotericin B (a *polyene)
2. Nystatin (a *polyene)
3. Griseofluvin
4. 5-Fluorocytosine (flucytosine)
5. Imidazole (and *azole)
6. Bistriazole (an *azole)
7. Naftifine (an *allylamine)
8. Terbinafine (an *allylamine)
9. Ciclopirox olamine
10. Tolnaftate |
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Term
| How does Amphotericin B work? What is it used for mostly? What are the side effects? |
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Definition
-It binds to **ergosterol in fungal membrane (polyene)
-It is used for most systemic infections
-It also binds to cholesterol to an extent, so it is nephrotoxic and can permanently damage renal basement membrane when used in high enough IV doses |
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Term
| What is the action of nystatin? What is it used for? |
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Definition
-It also is a *polyene and binds to **ergosterol
-However, unlike amphotericin B, it is used more *topically |
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Term
| What is the action of griseofulvin? What is it used for and how is it taken? |
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Definition
-It is given orally and over time is incorporated into keratin layers of skin where it interferes with **DNA replication
-Used for *dermatophytosis (ring worm)
-Has little to no side effects |
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Term
| What is the action of flucytosine? What do we use it for and with? Side effects? |
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Definition
-5-Fluorocytosine acts as a **nucleoside analogue which will be incorporated into fungal RNA and inhibit protein production
-It is used for urinary **candida albicans infections
-We often use it in conjunction with *amphotericin B for *systemic candidiasis (typically in immunocompromised)
-It is toxic and patients may become leukopenic |
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Term
| What are two types of imidazoles? What is the greater class imidazoles belong to? How does this class of antifungal antibiotics act? What do we use imidazoles for? |
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Definition
-Ketoconazole and miconazole are two types (other exist and most end in *-conazole)
-They belong to a class called **Azoles which inhibit **ergosterol synthesis by inhibiting **cytochrome P-450
-We use imidazoles topically for *dermatophyte infections (group that cause skin infections; like ring worm)
-*Ketoconazole can also be used as a second choice for deep fungal infections |
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Term
| What is the other type of azole? What are some examples of drugs in this class (2)? What is the advantage to using this type? What can we use it for? |
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Definition
-**Bistriazole antibiotics (also inhibit cytochrome P-450)
-Fluconazole and itraconazole are examples (all these also end in -conazole)
-They are less toxic than the other azoles when used intravenously
-We can use it to treat candidiasis in immunocompromised (like flucytosine), and a few other things |
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Term
| What are the two allylamine antibiotics? What is their action? What do we use them for? |
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Definition
-**Naftifine and **terbinafine
-They allosterically inhibit **squalene epoxidase which causes toxic accumulation of squalene and inhibition of *ergosterol synthesis (notice a lot of these inhibit ergosterol in some way)
-We use it topically for things like athletes foot and ringworm |
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Term
| What are the last two antifungal antibiotics? How do they act? What are they used to treat? |
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Definition
-Ciclopirox olamine; inhibits transport
-Tolnaftate; inhibits squalene epoxidation and lipid synth
-Mostly for **dermatophyte infections (*griseofulvin & *imidazoles are also used for this) |
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