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PH1123 Microbiology > Fungi > Flashcards

Fungi Flashcards

(66 cards)

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1
Q

Which bacteria are able to produce penicillin?

A

Penicillum Chrysogenum

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2
Q

How do fungi reproduce?

A

Sexually and asexually

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3
Q

How do moulds reproduce?

A

by producing spores

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4
Q

which domain of life do fungi belong to?

A

Eukaryotic

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5
Q

what are the benefits of fungi/yeast

A
  • alcohol beverage production
  • antibiotic production
  • bread
  • recombinant proteins
  • enzymes
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6
Q

how do fungi grow?

A

they grow as single cells

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7
Q

how do moulds grow?

A

overlapping and interlinking hyphal filaments

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8
Q

what is the asexual mode of reproduction used by fungi?

A

budding / fission

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9
Q

define mycoses

A

infection caused by any fungus that invades the tissues

or

diseases caused by fungal infections

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10
Q

what are the different types of mycoses?

A

1- superficial: white Piedra/ pityriasis versicolor
2- cutaneous: tinea pedis/ onychomycosis/ tinea capitis
3- subcutaneous: chromoblastomycosis/ mycetoma
4- systemic: blastomycosis/ histoplasmosis/ coccidiomycosis

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11
Q

list 3 oppotunistic fungal infections

A

1- candidiasis
2- aspergillosis
4- pneumonia

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12
Q

describe the structure of a yeast cell

A

oval with a rigid cell wall

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13
Q

what are the components of a yeast cell wall?

A

50-60% glucan
(beta-1,6-glucan/beta-1,3-glucan/beta-1,6 complexed with chitin)
25% polysaccharides
15-23% mannan
1-9% chitin

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14
Q

what are the three types of glucan in a yeast cell wall

A

beta-1,6-glucan
beta-1,3-glucan
beta-1,6 complexed with chitin

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15
Q

what is the role of mannoproteins in the cell wall?

A

they form a fibrillar layer that radiates from an internal skeletal layer that is formed by polysaccharides of the cell wall which limits wall permeability to solutes by covalent bonds

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16
Q

what would happen if the cell wall of fungi was removed?

A

it would leave an osmotically fragile protoplast which will burst if not maintained in an osmotically stable environment

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17
Q

what is a protoplast?

A

a cell with a removed cell wall

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18
Q

what is the role of beta-1,3-glucan in the cell wall of fungi?

A

1- provides physical protection
2- maintains osmotic stability
3- it is a scaffold for proteins
4- it mediated cellular communication
5- it is the site of enzymatic reactions

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19
Q

what is the periplasmic space?

A

thing region that lies below the cell wall

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20
Q

what is the plasmalemma?

A

phospholipid region located directly below the periplasmic space

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21
Q

what is the composition of plasmalemma?

A
  • phospholipids
  • lipids
  • proteins
  • sterols
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22
Q

why does the nuclear membrane of the fungal cell contain pores?

A

to allow communication between the nucleus and the rest of the cell

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23
Q

what are the mitochondrial enzymes and where are they located within the mitochondria?

A
  • Matrix: Krebs cycle enzymes
  • inner membrane: electron transport & oxidative phosphorylation enzymes
  • outer membrane: lipid biosynthesis enzymes
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24
Q

TRUE OR FALSE:
the mitochondria has its own DNA and is capable of synthesizing its own proteins, known as mitoribosomes

A

طبعا صح يعني -.-

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25
what are polysomes?
ribosomes of the fungal cell which are strung together by mRNA they are also the site of protein biosynthesis
26
Draw a fungal cell
you should've drawn it cheater
27
what are the classes of antifungal drugs?
- Polyene antifungals - Azole antifungals - Echinochandins - Synthetic antifungals
28
1- what is the mechanism of action of polyene antifungals? 2- name two polyene antifungal drugs
1- binds ergosterol, the dominant sterol in fungal cells, thus increasing membrane permeability by formation of pores and allowing intracellular components to escape 2- amphoterecin b / nyastatin
29
1- what is the mechanism of action of azole antifungals? 2- what are the subclasses of azole antifungals? 3- name two azole antifungal drugs
1- interfere with ergosterol biosynthesis by binding to cytochrome P450mediated enzyme (14 alpha demethylase), this prevents lanosterol methylation which prevents lanosterol from becoming ergosterol. thus, lessening the amount of ergosterol in cell wall leading to membrane instability, growth inhibition and cell death 2- imidazoles / triazoles 3- ketoconazole / itraconazole
30
1- what is the difference between imidazole antifungals and triazole antifungals? 2- give an example of an imidazole and a triazole
1- imidazoles have two nitrogen atoms in the 5 membered sugar whereas triazoles have 3 nitrogens 2- imidazole: ketoconazole triazole: itraconazole/ voriconazole
31
1- what is the mechanism of action of echinocandins?
target the synthesis of b-1,3-glucan which is the major polymer of the cell wall as it provides physical protection, maintains osmotic stability, regulates cell shape..etc therefore inhibition of its synthesis disrupts the structure of the growing cell wall resulting in osmotic instability and intracellular components would leave the cell leading to cell lysis
32
what are the subclasses of echinocandins?
- caspofungin - micafungin - anidulafungin
33
1- what is the mechanism of action of synthetic antifungal agents? 2- what is one example of a synthetic antifungal?
1- synthetic antifungals can work in either of two mechanisms - disruption of protein synthesis by inhibiting DNA synthesis - Depletion in the amino acid pools within the cell as a result of protein synthesis inhibition 2- flucytosine
34
List six fungal pathogens
1- candida albicans 2- aspergillis fumigatus 3- histoplasma capsulatum 4- dermatophytes 5- cryptococcos neoformans 6- saccharomyces cervisae
35
What morphological forms can candida albicans exist as?
- blastospores - hyphae
36
what patients are at risk of candida albicans?
diabetics burns/wounds indwelling urinary catheter cystitis trauma underlying disease organ transplant
37
how does candida albicans cause disease?
candida albicans is an opportunistic fungal pathogen, which means it is present in the normal microflora, however it only manifests as a disease when the microflora is disrupted
38
what is thigmotropism?
the ability to sense and respond to changes in surface contours, which aids in finding the line of least resistance in the host tissues
39
how does candida albicans bind to platelets?
via fibrinogen binding ligands resulting in fungal cell being surrounded by a cluster of platelets
40
what are the extracellular enzymes of candida albicans? and what is their function?
1- phospholipase A 2- phospholipase B 3- phospholipase C 4- lysophospholipase their function is to aid adherence and degredation of IgG/IgA immunoglobulins
41
what are the most clinically common candida species?
``` candida albicans candida glabrata (resistant) ```
42
who is at risk of candida parapsillosis?
neutropenic patients patients on broad spectrum antibiotics ICU patients Patients on parenteral nutrition catheter associated
43
What can disrupt the normal flora?
* *1- antimicrobial agents:** allows candida proliferation on mucosa and maceration of skin * *2- decreased t cell immunity**: allow candida proliferation on mucosa * *3- neutropenia:** allows candida to escape from gut to bloodstream * *4- central venous catheter:** allows entry to blood stream
44
what is the main host defense against candida albicans?
t cell mediated immunity and neutrophils in mucosa
45
why is it that HIV patients have frequent oropharyngeal and vaginal candidiasis?
because HIV patients have low counts of CD4 lymphocytes making them susceptible to candidal infections
46
in a neutropenic patient, where does candida occur?
eyes/kidneys/heart/brain/liver/spleen
47
how is candida diagnosed?
scrapings/ blood culture/ germ tubes for differentiation
48
what is candidemia?
A Candida bloodstream infection
49
what are the symptoms of candidemia?
candidemia symptoms depend on the end organ and can manifest as meningitis or chorioretinitis abscess
50
who is at risk of cryptococcus neoformans
AIDS Hematologoic malignancies transplant corticosteroids immunosuppressant drugs
51
what is the virulence factor of cryptococcosis?
polysaccharide capsule, which inhibits phagocytosis of immune responses thus downregulating Th1 mediators development
52
how is cryptococcosis diagnosed?
lumbar puncture where fluid will show lymphocytes/ high proteins/ decreased glucose
53
how is cryptococcosis treated?
amphoterecin B + flucytosine for two weeks after that, fluconazole for a few months
54
how does cryptococcus neoformans protect its cell wall?
by producing melanin that resist enzyme degradation of the host immune response
55
what are the most common aspergillus causing pathogens?
Aspergillus fumigatus + aspergillus flavus
56
who is at risk of aspergillus?
neutropenic corticosteroids transplant immunosuppressant drugs
57
how do aspergillus species cause disease?
after entry to the body, they germinate and turn into hyphae which invade tissues thus causing disease
58
main host defenses against aspergillus
* neutrophils macrophages
59
how do neutrophils defend against aspergillus
they line up along their surfaces & secrete reactive oxygen intermediates that kill the organism
60
how do macrophages defend against aspergillus?
pulmonary macrophages phagocytose and kill conidia but unable to kill hyphal forms
61
what damage does aspergillus cause?
tissue infarction/ haemorrhage/ necrosis
62
how is aspergillus diagnosed?
chest radiograph computed tomography scan tissue biopsy
63
how is aspergillus treated?
amphoterecin b echinocandin
64
define dermatophytes
they are keratinophilic fungi that metabolize keratin, which is abundant in the skin
65
what fungal pathogens cause tinea pedis (athlete's foot)?
* epidermophyton floccosum * trichophyton rubrum
66
are tinea infections contagious?
yes

PH1123 Microbiology (9 decks)

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