Introduction to Clinical Mycology
|What are mycotoxins?|| ergot alkaloids-pschotropic toxins, salem witch trials-grains suspetible|
aflatoxin-heptatoxin potent can be found in peanut butter
stachybotrys-black mold, grows in homes, not all black mold
|How frequent are fungal allergens? Why do so many people have allergens?||100,000 to more than 1 billion spores per square meter of air.|
|Describe the fungal cell. What makes it unique in terms of being a eukaryotic cell?|| |
Cell wall-made up of compounds that are completely different from bacteria,
Egosterol is the predmoinate sterol in fungal membranescomposition-major target for antifungal drugs
CHolesterol is the predominate sterol in mammalian
|Describe the cell wall of the fungus function.|
|What is the fungal cell wall composition?|| |
mannan, glucan and chitin
mannosylated proteins are common
|What is the function and structure of the fungal cell membrane?|| |
Ergosterol is important to remember
|What are the various classifications and structures of fungus?|| |
Dimorphic can vary on where it is located, slash temperature
|Describe yeast.|| |
Budding is also called blastoconidia
|What happens when yeast transforms|
Under proper conditions some yeast form structures known as pseudohyphae.
Candida albicans produces a structure known as a germ tube. A germ tube-an aborted budding process, long tube, diagnositc of this organism.
something that is low pathogen it is growing its yeast form, when something triggers it to become more invasive the pseudohyphae forms this happens. No separation, cell remained stucked together.
|What are molds? What are major structures of mold?|
Hairy or fuzzy looking
We don't do assays to diagnosis, we diagnosis by growing and looking at these structures are to determine what the species are.
Hyphae-are tube or ribbon shaped in appearance
Mycelium-mass of intertwined hyphae
vegetative or aerial-fuzzy mold on fruit sometimes
Septa (septum)-crosswalls which divide the hyphae
Septate-molds which form septa
Aseptate (coenocytic)-molds which do not possess these cross walls in their hyphae
Conidia-reproductive units produced asexually
Spore-products of sexual union
Conidiophores-stalk like structures that produce conidia
Microconida-small conidia, what we inhale
Chalmydoconidia or Arthroconidia-conidia which form within a hyphal element
|How do molds reproduce?|| Reproduction|
| Describe these the various types of fungal infections.|
Cutaneous mycoses-more common in clinical
subcutaneous mycoses-more common in tropical, can affect muscle or fascia-soil containtments
| Describe these various type of fungal infections.|
Systemic mycoses-nasty dimorphic, mold in environment, in our tissue yeast
Opportunistic mycoses- immunosuppressed individuals
|Describe the host response to fungal infection.|
The severity of disease caused by fungi depends upon the size of the inoculum (how many spores you inhale), magnitude of tissue destruction, the ability of the fungi to multiply in tissues, and the immunologic status of the host.
Most evidence supports little role for humoral immunity (antibodies).
Cell mediated immunity is essential for controlling and eliminating infection
Immunosuppression - steroids, radiation
T-cell and neutrophil deficits
|Describe different treatment for fungal infections using antifungual drugs.|| |
More toxic bc they are targeting eukaryote cell and don't have very many differences to exploit.
| Describe these drug actions, their targets.|
Know all of the ones in the table but all you need to know about these below
Polyenes-amphotercin B is the major one, binds to ergosterol
Azole-inhibit ergosterol biosynthesis
Allylamines, Thiocarbamates, and morpholines all inhibit Ergosterol bio-synthesis
Griseofluvin-interacts microtubules and inhibits mitosis
|How does Amphotericin B work?|| |
Ampha terrible-very toxic, bc it binds ergosterol mostly, and sometimes targets our cholesterol. Widely used for systemic diseases.
Ampha eventually insets itself into the cell membrane eventually forming pores which increase membrane permeability leading to cell death.
|What is the mechanism for ergosterol synthesis? What drugs inhibit ergosterol synthesis?|| |
Azoles, allyamines, thiocarbamates, morpholines
|How do we use lab to diagnosis fungal infection?|
|Describe KOH preparation|| |
KOH degrades host tissue cells, leaving behind only the more rigid cell walls or yeast and molds.
|What are special stains used for fungus?|| |
Cholrazol black-stains the chitin in fungal walls green/black, used to diangose of deratophyt infections
Calcofluor white stain-used in combination with KOH preps, dye will bind to fungal cell wall and fluoresce under UV light
|What happens if you gram stain a fungus?|| |
ALL FUNGI STAIN GRAM POSITIVE
| What kind of stain would you use for |
Cryptococcus neoformans pathogenic yeast causes fungal meningitis.
India Ink Stain-the capsule prevents the penetration of the ink into the fungal cell, resulting in the apperance of the yeast surrounded by a clear halo against the balck ink background.
|What kind of test would you use for candida albicans?|| |
Germ Tube Test-when inoculate into human serum and incubated at 37C, C. albicans produces a hyphal like extension following 1-3 hrs of incubation. Germ tubes are generally half the width and 3-4 times the length of the yeast cell from which they arise.
|What are some characteristics of how fungi grow in the lab?||Media may contain inhibitory substances such as chloramphenicol, gentamicin, or cycloheximide to prevent the growth of bacterial contaminants or saprophytic moulds. |
These may also inhibit opportunistic fungi and yeast, therefore it is important to use media with and without inhibitory agents.
Routine fungal cultures are incubated at 25-30 C for 3-4 weeks .
|What are example of some agars used for cultivation?|| Examples:|
Sabouraud's dextrose agar-one of the more common agars used in the cultivation of pathogenic fungi
Czapek Dox agar