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Microbiology E-Books > Fungi I > Flashcards

Fungi I Flashcards

1
Q

Their biochemistry and molecular biology are resemble those of mammalian cells

A

Fungi

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2
Q

Molecular genetic analysis has shown that many components of the cellular machinery required for protein synthesis and secretion, transcription, DNA replication, and control of cell division are functionally interchangeable in

A

Human and Fugnal Cells

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3
Q

Fave thick rigid cell walls that contain long-chain polysaccharides and highly-glycosylated proteins

A

Fungi

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4
Q

The impermeable cell wall limits access of drugs to the

A

Cytoplasm

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5
Q

An important wall component

-A polymer of D-mannose, bound to proteins

A

Mannan

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6
Q

A ‘mannose-binding protein’ in serum, resembles C1q; it binds fungal walls and activates

A

Complement

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7
Q

Fungi obtain nutrients and energy by breaking down organic matter, meaning they are

A

Saprophytes

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8
Q

Because of their rigid walls fungi are incapable of

A

Phagocytosis

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9
Q

Fungi - especially their cell walls - are potent

A

Immunogens

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10
Q

Growing [= vegetative] fungi divide by

A

Mitosis

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11
Q

In vegetative growth fungi produce thick-walled

-specialized for dispersal and resistance to unfavorable environments

A

Asexual spores (conidia)

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12
Q

When conidia encounter favorable nutrition, they germinate and resume growth. The mitotic mode of growth is the

A

Imperfect State

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13
Q

Many diploid fungi also undergo meiosis. The haploid products of meiosis are not gametes but thick-walled

A

Sexual Spores

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14
Q

Two haploid cells of different mating type can fuse to produce a diploid cell. The ability to go through meiosis and produce sexual spores is the

A

Perfect State

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15
Q

Takes place only under strictly-defined conditions, often involving starvation, and seldom takes place in mammalian tissue

A

Meiosis

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16
Q

So, although sexual structures determine classification of fungi, they are of little use in the

A

Identification of pathogens

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17
Q

Easily airborne and resistant to heat, cold, and drying.

-They are widespread in the environment

A

Fungal Spores

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18
Q

Pose a major health problem for severely immunocompromised patients

A

Fungal Spores

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19
Q

Immune defense against fungi is provided mostly by

A

Phagocytes

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20
Q

Neutropenic patients (for example, those who receive radiation therapy for cancer) are highly susceptible to

A

Fungal Infections

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21
Q

A a structural analogue of cytosine

A

5-fluorocytosine

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22
Q

Fungi convert it to 5-fluorodeoxyuridine monophosphate, an analogue of dTMP

A

5-fluorocytosine

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23
Q

Inhibits synthesis of thymine and blocks fungal DNA synthesis

A

5-fluorocytosine

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24
Q

Because genetic resistance regularly emerges, 5FC is used in combination with

A

Amphotericin

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25
Q

Membrane inhibitors exploit one of the few differences between fungal and mammalian cells: Mammalian membranes contain cholesterol, while those of fungi contain the related steroid

A

Ergosterol

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26
Q

Bind to ergosterol in the membrane, increase membrane permeability and cause loss of small molecules from the cell

A

Polyenes

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27
Q

What are two polyenes that serve as membrane inhibitors?

A

Amphotericin and Nystatin

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28
Q

Used for systemic or deepseated infections

A

Amphotericin

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29
Q

Too toxic for internal use but is used topically for fungal infections

A

Nystatin

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30
Q

What are the four types of fungal membrane inhibitors?

A

Polyenes, Azoles, Echinocandins, and Pentamidine

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31
Q

Interfere with the synthesis of ergosterol

-The best antifungals

A

Azoles

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32
Q

Block synthesis of cell-wall polysaccharides

A

Echinocandins

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33
Q

Used against Pneumocystis carinii, a common cause of pneumonia in AIDS patients, and recently discovered to be a fungus

A

Pentamidine

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34
Q

Pneumocystis genes which encode ribosomal RNA contain introns that splice themselves out of rRNA transcripts without participation of the normal cellular splicing apparatus. This self-splicing is inhibited by

A

Pentamidine

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35
Q

No example of a self-splicing intron is found in mammalian DNA; this accounts for pentamidine’s

A

Selective toxicity

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36
Q

What are the four major groups of fungi?

A

Zygomyces, Ascomyces, Basidiomyces, and Deuteromyces

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37
Q

Many sexual spores are produced in a large sack-like zygospore, produced at the position at which two haploid cells have fused

A

Zygomyces

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38
Q

What are two important pathogenic zygomycetes?

A

Rhizopus and Mucor

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39
Q

Single cells undergo meiosis and the resulting four haploid spores are contained in a sac [ascus], derived from the wall of the original diploid cell

A

Ascomyces

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40
Q

What are two important non-pathogenic ascomycetes?

A

Bread and Brewers yeast

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41
Q

Diploid nuclei in a club-like structure (basidium) undergo meiosis and haploid spores bud in chains from the tip of the basidium

A

Basidiomyces

42
Q

What is an example of an important basidiomycete?

A

Cryptococcus and poisonous mushrooms (Amanita)

43
Q

What is an important non-pathogenic basidiomycete?

A

Edible mushroom

44
Q

No known sexual stage. However, perfect fungi undergo meiosis only under specific conditions, it is not often known whether a deuteromycete is truly incapable of meiosis or whether the appropriate conditions have simply never been found

A

Deuteromyces [= fungi imperfecti]

45
Q

The sporangium contains haploid spores formed by meiosis created by fusion of hyphal tips of two mating types

A

Zygomycete

46
Q

Diploid nucleus goes through meiosis to produce 4 haploid nuclei. Each divides again, then forms a spore wall around itself

A

Ascomytcete

47
Q

Fungi are non-fastidious. They are cultured on media such as

A

Saboraud’s medium

48
Q

Contains protein hydrosylate and glucose

A

Saboraud’s medium

49
Q

For culture, a few pathogenic fungi require

A

Blood agar

50
Q

Cannot be cultured at all except in the lungs of immunosuppressed rats

A

Pneumocystis

51
Q

Fungal plates are usually incubated for 30 days before being reported as

A

Negative

52
Q

Dark-pigmented colonies are called

A

Dematiacious

53
Q

Non-pigmened colonies are called

A

Hyaline

54
Q

The dark pigment aids

A

Virulence

55
Q

Unlike bacteria, many fungi have diagnostic

A

Morphology

56
Q

Identification depends heavily on morphology of

A

Asexual forms

57
Q

Mammalian cells are destroyed but the thick walls of fungi resist alkali, so become easier to see in tissue. Easy and rapid staining technique

A

Drop of KOH

58
Q

This fluorescent dye binds to the polysaccharide in fungal walls

-Requires a fluorescence microscope

A

Calcofluor

59
Q

Which two stains show fungi in tissue sections?

A

Methenamine silver and PAS stains

60
Q

Molds or filamentous fungi have cells arranged in filaments called

A

Hyphae

61
Q

The mass of hyphae forms a

A

Mycelium

62
Q

Cell division is by transverse fission; cross-walls [septa] are present in ascomycetes and basidiomycetes but are rare or absent in

A

Zygomycetes

63
Q

Colonies of filamentous fungi appear

A

Fluffy or powdery

64
Q

Unicellular fungi that reproduce by budding

-Formation of a new cell begins with a small bulge in the wall of an existing cell; the bulge progressively enlarges, nuclear division takes place, one of the daughter nuclei migrates into the bud, and a septum forms that separates the two cells

A

Yeasts

65
Q

If progeny cells remain persistently attached, they are said to form

A

Pseudohyphae

66
Q

Yeast colonies usually appear

A

Moist or creamy

67
Q

Dimorphic fungi grow as yeasts in the rich environment of the body (or on blood agar) at

A

37 degrees C

68
Q

Grow as hyphae on poor medium (Saboraud’s) at 30C

A

Dimorphic Fungi

69
Q

Hyphal forms produced in laboratory culture are not easy to distinguish, but the yeast forms in tissue have distinctive

A

Morphology

70
Q

Small and contain only a single cell

A

Microcanidia

71
Q

Large and contain multiple cells

A

Macroconidia

72
Q

Macroconidia form by differentiation of a length of hypha. An example of this is

A

Trichophyton

73
Q

Form by fragmentation of hyphae at septal planes

A

Arthroconidia

74
Q

Form by differentiation of the terminal cell of a hypha

-They are large, round, and thick-walled

A

Chlamydospores

75
Q

Arise by budding from the tip of a specialized flask-shaped cell

A

Phialoconidia

76
Q

Phialoconidia may be produced as single cells or in chains. Two examples of this are

A

Aspergillus and penicillium

77
Q

Produced by budding [Example: Cryptococcus.]

A

Blastocondia or blastospores

78
Q

Form large numbers of asexual spores contained in a sac (sporangium), borne at the top of a stalk

A

Zygomycetes

79
Q

What are the four forms of pathogenic fungal infections?

A

Superficial, Cutaneous, Subcutaneous, and Systemic

80
Q

Mycoses involve the outermost cornified layers of skin, hair and nails, without invasion of deeper tissue

A

Superficial fungal infections

81
Q

Mycoses involve only the skin, again without invasion of subcutaneous tissue

A

Cutaneous fungal infections

82
Q

Mycoses are localized infections of deeper tissue, without spread to distant sites

A

Subcutaneous fungal infections

83
Q

Mycoses start as a focal infection, often of the lung, and spread elsewhere

A

Systemic fungal infections

84
Q

A relatively small number of fungi are primary pathogens, capable of infecting a healthy host. A much larger number are opportunists, infecting the

A

Immunocompromised

85
Q

Produced by fungi of low virulence; little inflammation

A

Superficial mycoses

86
Q

May develop hyper- or hypo-pigmentation

A

Skin infections (pityriasis)

87
Q

Fungi grow not on skin but in or on hair shafts in

A

Piedra

88
Q

Piedra is diagnosed by microscopic examination of a scraping from the infected site. Hair infections are fluorescent; can be visualized under a

A

UV (woods) Lamp

89
Q

Fungi that cause cutaneous mycoses are called

A

Dermatophytes

90
Q

Cutaneous infections are called

-followed by a latin adjective that describes the sight infected

A

Tinea

91
Q

What do the following affect?

  1. tinea corporis
  2. tinea capitis
  3. tinea cruris
  4. tinea pedis
  5. tinea unguium
  6. tinea barbae
A
  1. Body/skin (ringworm)
  2. Scalp/hair
  3. Groin
  4. Feet
  5. Nails
  6. Beard
92
Q

Lesions expand, with a rim of active infection and inflammation and a central area of healing. Scrapings for diagnosis should be taken from the

A

Rim, not the center

93
Q

What are the three important genera of dermatophytes?

A

Epidermophyton, Microsporum, and Trichophyton

94
Q

Distinguished by the presence or absence of microconidia and appearance of macroconidia

A

Dermatophytes

95
Q

Infections of skin and subcutaneous tissue, usually localized and not spreading

A

Subcutaneous mycoces

96
Q

Lesions, often on the extremities, form ulcers or papules

A

Subcutaneous Mycoces

97
Q

A subcutaneous mass of fungi surrounded by granulomatous inflammation is a

-Similar lesions are produced by Actinomycetes

A

Mycetoma

98
Q

A common cause of subcutaneous infections [sporotrichosis]

A

Sporothrix schenkii

99
Q

S. schenkii is dimorphic. Cells in the yeast phase are long-oval or

A

Cigar shaped

100
Q

Histoplasma capsulatum, Blastomyces dermatitidis, Coccidiodes immitis, and Paracoccidiodes braziliensis are all species that cause

A

Systemic mycoses

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