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General - Microbiology 🦠 > L5: General Mycology > Flashcards

L5: General Mycology Flashcards

1
Q

What is the morphology of fungi?

A

There are three main groups of fungi based on cell morphology:

  • Yeast and Yeast-like
  • filamentous (hyphae)
  • dimorphic fungi
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2
Q

What is the definition of Yeast and yeast-like fungi?

A
  • Yeasts are round to oval unicellular fungi which reproduce by budding or fission, a progenitor then detached from the mother cell, e.g. (Cryptococcus neoformans).
  • Yeast-like is round to oval multi-cellular fungi reproduce by budding but a progenitor remains attached to the mother cell giving a chain of elongated yeast cells called pseudohyphae. e.g. (Candida).
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3
Q

What is the definition of filamentous fungi?

A
  • Filamentous fungi (hyphae) are tubular, branching structures that may or may not be separated by porous cross-walls (septa) forming septated or aseptated hyphae.
  • The part of the hyphae that anchor the colony, absorbs nutrients is termed vegetative hyphae.
  • The part that projects above & carries the reproductive structure called aerial hyphae.
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4
Q

What is the definition of dimorphic fungi?

A

Dimorphic fungi exist either as yeast or as filaments depending on the condition of growth.

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5
Q

What are examples of dimorphic fungi?

A

Coccidioides immitis
Histoplasma capsulatum
paracoccidioides brasiliensis
lastomisis demesis

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6
Q

How do fungi reproduce?

A

Fungi reproduce by the formation of spores either asexual or sexual

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7
Q

What are the types of asexual spores?

A

There are two general types of asexual spores:

a. Sporangiospore
b. Conidiospore

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8
Q

What are sporangiospores? And where does it happen?

A

 Some fungi during growth form sac filled with spores.
 They are mitotic spores produced within a sac termed sporangium often supported by one hyphae termed sporangiophore and this type of spores exists on non-septated fungi.

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9
Q

What are the types of conidiospores?

A
  • Arthroconidia (Arthrospores): conidia that result from fragmentation of hyphae cell.
  • Blastoconidia (Blastospores): conidial formation through a budding process.
  • Phialoconidia: conidia that are produced by a (vase-shaped) conidiogenous cell termed a phialide. These spores formed at the terminal part of fertile hyphae.
  • Chlamydoconidia (Chlamydospores): large thick-walled resting spores developed from hyphae for existence during long periods of dormancy.
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10
Q

How are sexual spores formed?

A

During sexual reproduction, haploid cells of compatible strains mate through a process of plasmogamy, karyogamy, and meiosis to form transient diploid——> meiosis of this transient diploid to form sexual spores

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11
Q

What are the types of sexual spores?

A
  • Ascospores
  • Basidiospores
  • Zygospores
  • Oospores
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12
Q

What is the definition of ascospores?

A

four to eight meiospores form within a sac-shaped structure termed ascus.

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13
Q

What is the definition of basidiospores?

A

four meiospores usually form on the surface of a specialized club-shaped structure termed basidium.

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14
Q

What are zygospores?

A

a large thick-walled zygospore develops between two different hyphae.

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15
Q

What are oospores?

A

a large thick-walled zygospore develops within the same hyphae.

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16
Q

What are the harmful effects of fungi?

A
  1. Hypersensitivity reactions due to environmental exposure to fungal spores.
  2. Infection results from invasion Of tissue and organs.
  3. Toxicosis (With description)
17
Q

What are types of fungal toxicoses?

A

a) Mycotoxicosis: result from accidental consumption of food products contaminated by toxin-producing fungi e.g • Ergot alkaloids toxicosis
• Aflatoxicosis

b) Mycetismus: result from ingestion of fungi containing preformed toxin e.g: • Mushroom poisoning

18
Q

What is the classification of medically important fungi?

A

I. Primary pathogenic fungi:
Affect immunocompetent individuals e.g. dimorphic fungi

II. Opportunistic fungi:
Affect immunocompromised individuals e.g. candida (yeast-like)

19
Q

What is mycosis?

A

Mycosis means diseases caused by fungi.

20
Q

What are fungal infections classified according to?

A

Fungal infections are classified according to affected tissue or organ

21
Q

What are the types of mycosis?

A

I) Superficial mycosis
II) Cutaneous mycosis
III) Subcutaneous mycosis
V) Opportunistic mycosis

22
Q

What is superficial mycosis and what is an example for it?

A

 Strictly surface infections are limited to the outermost layers of skin and hair.

 Example:

  • Pityriasis versicolor
     Caused by Malassezia
     Clinically appear as blotchy hypo or hyperpigmented itchy macular lesions usually on the chest, back, abdomen, upper arm.
23
Q

What is cuteness mycosis and what is an example for it?

A

 Fungal infections that extend deeper into the epidermis, hair, and nail.

 Example:
* Dermatophytosis caused by dermatophytes
There are different clinical forms based on site of involvement:

  • Tinea capites
  • Tinea Barbae
  • Tinea unguim
  • Tinea pedis
  • Tinea corporis
  • Tinea cruris
24
Q

What does Tinea capitis affect? And what are its symptoms?

A

 Affecting the scalp & hair.

 Dull gray circular patches of alopecia with itching broken hair.

25
Q

What does Tinea barbae affect? And what are its symptoms?

A

 Affecting the beard hair.

 Edematous, erythematous lesion.

26
Q

What does Tinea ungium affect? And what are its symptoms?

A

 Affecting the nails.

 Thickened, yellow discoloration, lusterless brittle nail.

27
Q

What does Tinea pedis affect? And what are its symptoms?

A

 Affecting between toes.

Itching, development of small vesicles, rupture, toe webs become macerated, and peels.

28
Q

What does Tinea corporis affect? And what are its symptoms?

A

 Affecting non-hairy smooth skin.

 Advancing rings with scaly center and periphery are inflamed, vesiculated “site of active fungal growth”.

29
Q

What does Tinea cruris affect?

A

Affecting the groin, moist areas.

30
Q

What is subcutaneous mycosis and what is an example for it?

A

 Infection involving the dermis, subcutaneous tissue, muscle, and fascia.

 Example: *Mycetoma

31
Q

What is the definition of myectoma and what is it caused by?

A

 Caused by Madurell, Exophiala.

 The chronic subcutaneous infection progresses slowly and burrows into deeper tissue producing abscess which bursts with the formation of chronic sinuses discharging fluid containing granules.

32
Q

What is systemic mycosis? And what is it caused by?

A
  • Infections involve many organ systems.

 Caused by primary pathogenic dimorphic fungi.

33
Q

What are examples of systemic mycosis?

A

Histoplasmosis, Blastomycosis,

Coccidioidomycosis, Paracoccidioidomycosis

34
Q

What is opportunistic mycosis? And what are examples of it?

A

 Group of mycoses caused by saprophytic immunocompromised individuals.

 e.g. Candidiasis, Aspergillosis, and Cryptococcosis.

35
Q

What are the targets of anti-fungal therapy?

A

There are drugs that act on:

  1. Cell wall synthesis:
     Caspofungin: inhibit 1,3- β glucan synthetase enzyme———->Inhibit cell wall synthesis.
  2. Ergosterol synthesis:
     Polyenes: e.g. Amphotericin B, Nystatin: bind firmly to ergosterol in the fungal cell membrane forming pores—>disrupt membrane function—>cell death.
     Azoles: interact with cytochrome P450 dependent 14-α demethylase to inhibit demethylation of lanosterol to ergosterol.
  3. Cytoplasmic membrane function:
     Polyenes
     Azoles
  4. Nuclear division:
     Griseofulvin: interact with microtubules—>disrupt mitotic spindle function—>inhibit growth.
  5. Nucleic acid synthesis:
     5 fluorocytosine: converted by fungal enzyme cytosine deaminase into 5- fluorouracil which interferes with DNA synthesis.
  6. Protein synthesis: Blasticidin
  7. Metabolic inhibitors

General - Microbiology 🦠 (6 decks)

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