Lecture 11: Introduction to mycology Flashcards
Moulds divide
sexually or asexually
What is the difference in cell wall between bacteria and moulds
moulds have membrane bound organelles and a cell wall that is not held together by peptide bonds i.e no gram wall
what membrane bound organelles do moulds posess
nucleus, ribosomes through ER, cell wall, mitochondria, vacuole and a cell membrane
how is a mould membrane kept fluid
sterols
What sterol is found in moulds and is targeted with drugs?
ergosterol
What drugs target ergosterol
- amphotericin B and Nystatin bind ergosterol forming pores in the membrane
- Imidazole and allylamine drugs inhibit enzmyes in ergosterol biosynthesis
What is the purpose of antifungal treatment?
target unique features of fungal cells sucha s ergosterol in the cell membrane, glucan cell wall polymer and cytoseine deaminase
how do antifungl agents work on cytoseine deaminase
prevents the conversion of 5-Fluorocytosine to 5-Fluorourcil. this inhibits both protein sythesis and DNA synthesis
Function of Azoles
inhibit ergosterol biosythesis resulting in depletion of this sterol in the cell membrane
Function of polyenes
form pore channels resulting in cell death
Function of candins
inhibit cell wall synthesis, membrane pops - cant cope with osmotic pressure
How do yeasts grow?
divide by budding
Explain the process of budding
- bud begins to form on parent cell
- nucleus copies and divides, the bud receives a copy
- bud now becomes a separate daughter cell
- budding produces chains of cells
What is dimorphic growth as seen with Candida albicans
instead of budding, germ tube or hyphae produced which divide into other cells
____ are the main mode of vegetative fungal growth and are collectively called a ____. yeasts (except C. albicans) are ____ fungi that do not grow as hyphae.
Hyphae, mycelium, unicellular
Yeast cells are ____ to ____ shape and reproduce by ____, any ____ ____ occurs at the junction between mother and daughter cells. Progeny cells detach ____ from mother cells, cosidered ____
round, oval, budding, nuclear, division, completely, unicellular
Hyphal cells are ____, ____-shaped cells where nuclear divsion occurs within ____ ____ cells. This is followed by ____ of one progeny nucelus back into the mother cells. Hyphal cells remain ____ ____ end-to-end, rounds of cell divsion produce multicellular, sparsely branched, filamentous structures called ____ .
thin, tube, daughter cells, migtation, firmly, attached, mycelia
Pseudohyphal cells share features of both ____ and ____. Like hyphae, pseudohyphal cells remain ____ and generate ____ after multiple rounds of cell division. As in yeasts, nuclear divsion in pseudohypahe occurs at ____ to ____ ____; in contrast to hyphae, these junctions are demarcated by visible indentations
yeasts, hypae, attached, mycelia, mother, daughter, junctions
Chalmydospores are ____, ____, thich walled cells observed in vitro under certain harsh condtions such as ____ and ____, Chlamydosproes are generated by ____ cells which are cells at the distal end of mycelial filaments
large, spherical, starvation, hypoxia, suspensor
moulds grow in ____ form
hyphae
The fungi outgrowing from germinating candida are ____ ____. those germinating from ascospires are ____ ____.
genetically identical, genetically different
conidia
a type of asexual reproductive spore of fungi (kingdom Fungi)
Ascospores
A sexually produced fungal spore formed within an ascus of ascomycetes
mycoses
diseases caused by a fungus (yeast or mold).
mycoses: skin infections
ringworn and tinea
causative agents of ringworm and tinea
Dermatophytes - microsporum, trichophyton, epidermophyton
Mycoses: mucosal infections
trush
Causative agent of thrush
candida albicans
Mycoses: invasive infections
Sepsis, menigitis, pneumonia
Causative agents of invasive infections like sepsis, menigitis and pneumonia
candida, cryptococcus, aspergillus
Skin infections/cutaneous mycoses are ____ fungal infections of the skin, hair or nails. No living tissue is ____, however a variety of pathological changes occur. Often produce a range of ____
superficial, invaded, proteases
Examples of cutaneous mycoses
tinea pedis (athletes foot), tinea cruris, tinea corporis, ringworm, onychomycosis (nail infection)
Macrocondia vs microcondia
Microconidia: Small, unicellular conidia that are round, elliptical, or pyriform (pear-shaped).
Macroconidia: Large, multi-septate conidia that are club- or spindle-shaped.
How is Trichophyton rubrun and Epidermophyton floccosum spread?
they are antrhopophillic, prefer humans, spread by contact; towels, clothing and showers
How is microsporum canis spread?
cats and dogs main source of infection
Risk factos for aquiring cutaneous mycoses
high humidity, heat, perspiration, diabetes, obesity, friction from clothes, contact with containated linen or towels, contact with perts
Symptoms of cutaneous mycoses
itchoness, distinctive appearance, may fluoresce under black light (UV-A)
treatment options for mycosis
imidazoles and synthetic allylamines. –> block ergosterol synthesis leading to cell lysis
List three systemic mycosis infection s
opportunisitc aspergillosis
systemin candidiasis
cyryptococcal menigits
Pathogenesis of aspergillus
- airborne aspergillus conidia
- lungs
- Immunosuppression (HIV, cancer, etc) leads to lung infection
- hematogenous spread –> leads to infection of other organs
How is apergillosis infection diagnosed
Chest CT scan
microsocpy - fungal filaments with septate and acutely angles branching hypae with inflammatory cells in the pulonary parenchyma
they secrete **galactomannan ** which is detecatble in serum and lung fluid
aspergillosis treatment options
IV voriconazole, alternatives are other imidazoles and echinocandins
Pathogenesis of candida
- mucosal candida
- immunosupression leads to infected blodo
- hematogenous spread - infection of other organs
Candia is in the top ____ invasive pathogens by numver of cases. about ____ % of all cases, and has a ____% mortality rate
5, 9, 30
Treatment options for candidiasis
Amphotericin B - resistance developed, not used much
Fluconazole - #1 drug
Echinocandin - alternative to fluconazole
Crypotococcus pathogenesis
found in bird shit
- aerolised spores breathed
- lung
- immunosuppresion leads to lung infection
- hematogenous spread
- meningitis
How is cyrptococcus diagnosed
sputum - Enzyme immunoassays (EIA) are used to visualize and quantify antigens.
CSF - A cerebrospinal fluid (CSF) culture
Treatment options for cryptococcus
amphotercin B - intrathecal injection
5 fluorocytossine - oral or iv, inhibtor of DNA and RNA syntehsis
Alternatively - fluconazole and echinocandin
What happens upon persisten exposure to fungi
- increased exacerbation of symptoms
- risk of developing astham increaseses by 1.36x
- statistically significant increase in respiratroy infections and bronchitis
