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Medical Microbiology > Fungal pathogens > Flashcards

Fungal pathogens Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

What are the four characteristics of fungi?

A

Eukaryotic
Cell wall is made of chitin, glucans, or mannans
Ergosterol in the cytoplasmic membrane
Heterotrophic metabolism (Saprophytic and parasitic)

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2
Q

What are the three major types of fungal cell wall?

A

Can be made of:

Chitin
Glucans
Mannans

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3
Q

It is major sterol component of fungal cytoplasmic membrane which can be targeted for therapeutic purposes and leads to the lysis of the fungal cells.

A

Ergosterol

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4
Q

Fungi have heterotrophic metabolism, what are the two types of fungal lifestyle (modes of nutrition)?

A

Saprophytic - obtains nutrients by decomposing dead organic matter

Parasitic

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5
Q

What are the two types of fungal cell morphology?

A

Hyphae - many fungal cells aggregating to form the organism
Yeast - single-celled fungi

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6
Q

This refers to a mat or aggregate of hyphae.

A

Myceliun

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7
Q

Two types of hyphae

A

Coenocytic

Septate

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8
Q

In this type of hyphae, the cells compartmentalized by septum.

A

Septate

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9
Q

In this type of hyphae, the cytoplasm and organelles are continuous throughout the entire hyphal structure, without cellular compartments created by septa.

A

Coenocytic

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10
Q

These are fungi capable in switching to/from yeast and hyphal form during their life cycle.

A

Dimorphic (Pleomorphic) fungi

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11
Q

T/F. Coccidioides immitis has both yeast and hyphal forms (dimorphic).

A

True.

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12
Q

T/F. Coccidioides immitis is dispersible in the hyphal form.

A

False. Coccidioides immitis needs to fragment in order to be dispersed and is dispersible only in the yeast form.

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13
Q

This is a type of hyphae characterized by pronounced constrictions at each septum.

A

Pseudohyphae

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14
Q

What are the three types of fungal spores?

A

Conidia
Blastoconidia
Arthroconidia

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15
Q

This type of spores represent asexual spores, and are formed off of a hyphae.

A

Conidia

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16
Q

This form of spores buds on yeasts.

A

Blastoconidia r. germ tube

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17
Q

This form of spores are asexual spores formed by segmentation of hyphae

A

Arthroconidia

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18
Q

What are the stains used in the microscopic examination of fungus?

A

KOH wet mount
Silver
India ink

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19
Q

Culturing fungi is done on what medium?

A

Sabouraud Dextrose Agar with antibiotics

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20
Q

What are the diagnostic procedures in detecting fungal pathogens?

A

Microscopy (KOH, silver, and India ink staining)
Culture on SDA
PCR
Serology

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21
Q

What are the virulence factors associated with fungal pathogens?

A

Morphological transformation
Genetic switching of metabolic processes in response to the host environment
Cell wall component that resist phagocytosis
Production of surface adhesins
Formation of biofilms
Secretion of enzymes that attack host substrates

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21
Q

This term refers to diseases caused by fungi.

A

Mycoses

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22
Q

What are the general presentation of mycoses?

A

Cutaneous and superficial mycoses
Subcutaneous
Deep
Opportunistic

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23
Q

T/F. Malassezia furfur generally produces cutaneous mycosis.

A

True.

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24
Q

T/F. Malassezia furfur is part of the normal skin microflora.

A

True.

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25
Q

T/F. Malassezia furfur is lipophilic.

A

True.

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26
Q

What is the mildest presentation of M. furfur?

A

Dandruff

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27
Q

This condition caused by M. furfur is characterized by white, reddish, or pink spots that varies on severity based on skin color and exposure to sunlight.

A

Pityriasis versicolor
-hyperpigmented lesions for lighter skin
-hypopigmented lesions for darker skin

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28
Q

This organism causes Pityriasis versicolor characterized by white, reddish, or pink spots that varies on severity based on skin color and exposure to sunlight.

A

Malassezia furfur

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29
Q

What are the three presentation of Malassezia furfur infection?

A

Dandruff
Pityriasis
Folliculitis

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30
Q

What method is used for the diagnosis of Malassezia furfur?

A

KOH staining

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31
Q

These microorganisms are a class of filamentous fungi infecting only skin, hair, and/or nails.

A

Dermatophytes

32
Q

What are the three genera of dermatophyte fungi?

A

Trichophyton (infects skin, hair, and nails)
Microsporum (infects hair and skin only)
Epidermophyton (infects nails and skin only)

33
Q

T/F. Dermatophytes secrete keratinase and lives on dead, and horny skin layer.

A

True.

34
Q

This disease produced by Dermatophytes is characterized primary by itching.

A

Tinea

35
Q

This tinea affects the groin and is most commonly referred to as jock’s itch.

A

Tinea cruris

36
Q

This tinea affects the scalp.

A

Tinea capitis

37
Q

This tinea affects the nails.

A

Tinea unguium

37
Q

This tinea affects the hairless skin and is commonly referred to as ringworm.

A

Tinea corporis

38
Q

This tinea affects mainly the lower legs and is more commonly referred to as athlete’s foot.

A

Tinea pedis

39
Q

This tinea affects the scalp hair.

A

Tinea capitis

40
Q

This tinea affects the beard hair and more commonly referred to as beard ringworms.

A

Tinea barbae

41
Q

This mycosis of the nails is caused by various dermatophytes and Candida spp.

A

Onychomycosis

42
Q

This class of organism primarily causes tinea mycoses in humans.

A

Dermatophytes

43
Q

This type of mycosis is caused by environmental fungi associated with vegetation and soil.

A

Subcutaneous mycoses

44
Q

T/F. Subcutaneous mycosis infections are acquired due to the inoculation of fungi into minor cuts or scratches on the skin.

A

True.

45
Q

T/F. Dermatophytes generally produce subcutaneous mycoses.

A

False. Cutaneous mycosis, i.e., tinea.

46
Q

This type of mycosis is limited to chronic infections but rarely spread to deeper tissues.

A

Subcutaneous mycosis

47
Q

This subcutaneous mycosis is characterized by the development of slowly growing, warty, and nodular skin lesions, often with a distinctive appearance due to the presence of dark, sclerotic (hardened) fungal cells known as chromoblasts.

A

Chromoblastomycosis

48
Q

What are the known causative agents of chromoblastomycosis?

A

Fonsecaea pedrosoi
F. compacto
Cladosporium carionii
Phialophora verrucosa

49
Q

Introduction of chromoblastomycosis-causing fungus into the body is usually achieved through?

A

Punctures, thorns, splinters, etc.

50
Q

This disease is characterized by the formation of painless, tumorous swellings, sinuses, and discharge of grains or granules from the affected area.

A

Mycetoma

51
Q

What is the causative agent of mycetoma?

A

Pseudallescheria boydii
Nocardia brasiliensis

52
Q

This disease is characterized by the formation of skin lesions and is sometimes referred to as “rose gardener’s disease” due to its association with plant-related activities.

A

Sporotrichosis (infection through small cuts or scrape)

53
Q

T/F. Sporotrichosis is a deep mycosis.

A

False. Subcutaneous

53
Q

What are the subcutaneous mycoses?

A

Chromoblastomycosis
Mycetoma
Sporotrichosis

53
Q

This disease starts as a respiratory infection when conidia are inhaled, resembling TB during early infection. It is also known as Cave’s disease due to the association of the fungi with soil laced with bird, chicken, or bat feces.

A

Histoplasmosis caused by Histoplama capsulatum

54
Q

T/F. Histoplasmosis is a disease endemic in Mississippi-Ohio river valley, Africa, East Asia, and Australia.

A

True.

55
Q

This disease starts as a respiratory infection when conidia are inhaled. Causative agent fungi is characteristically found in sand and desert environments.

A

Coccidioidomycosis caused by Coccidiodes immitis

55
Q

T/F. Coccidiodes immitis is a dimorphic organism.

A

True. Mycelium in soil, and spherules in tissue

56
Q

What form does Coccidiodes immitis take in soil?

A

Mycelium

57
Q

What form does Coccidiodes immitis take in tissue?

A

Spherules

58
Q

What are the deep mycosis?

A

Histoplasma capsulatum
Coccidioidomycosis

59
Q

This type of mycosis is caused by globally distributed fungi, and elicits the highest incidence, severity, and mortality.

A

Opportunistic mycoses

60
Q

Diagnosis of this type of mycosis is often difficult but early diagnosis, immediate antifungal therapy, control of underlying condition ensures successful management. Innate host defense provide crucial protection too.

A

Opportunistic mycoses (aspergillosis or candidiasis)

61
Q

Aspergillus fumigatus generally produces what type of mycosis?

A

Opportunistic mycosis

62
Q

This fungus enters the respiratory tract and produces toxic metabolites to inhibit the immune system.

A

Aspergillus fumigatus

63
Q

What are the presentation of Aspergillus fumigatus infection?

A

Aspergilloma
Aspergillosis
Invasive aspergillosis

64
Q

This fungus is an indigenous yeast in the oral mucosa, forms pseudohyphae and germ tubes.

A

Candida albicans

65
Q

What are the disease produced by Candida albicans?

A
  • Perleche
  • Thrush
  • Esophagitis
  • Gastritis
  • Endocarditis
  • Vaginitis
66
Q

This disease is caused by inhalation of spores of the causative agent fungi usually associated with pigeon droppings. It starts as a pulmonary infection but later may affect the CNS, skin, and bones.

A

Cryptococcal meningitis caused by Cryptococcus neoformans

67
Q

This antifungal drug works by binding to ergosterol component of the fungal cytoplasmic membrane, usually used for systemic fungal infections, and is delivered through an IV.

A

Amphotericin B

68
Q

This antifungal drug works by inhibiting Cytochrome P-450 which is related in the synthesis of ergosterol.

A

Azole antibiotics

68
Q

This antifungal drug works by inhibiting DNA/RNA synthesis, is best administered with Amphotericin B, and is delivered through an IV.

A

Flucytosine

69
Q

This antifungal drug works by inhibiting ergosterol, is too toxic to be used through IV, and is not absorbed via GI tract and, therefore, used to treat mouth and esophageal fungal infections.

A

Nystatin

69
Q

This anti fungal drug is used for slow cure of skin mycosis and works by inhibiting spindle formation.

A

Griseofulvin

69
Q

This anti fungal drug accumulates in the nails, is best for treating fungal nail infections, and blocks fungal cell wall synthesis.

A

Terbinafine

70
Q

What are the side effects of Amphotericin B

A

Renal toxicity, fever, and anemia

71
Q

What are the side effects of Flucytosine?

A

bone marrow depression, nausea, vomiting, and diarrhea

Medical Microbiology (9 decks)

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