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Microbiology > Mycology Exam 1: Intro + Dermatophytes > Flashcards

Mycology Exam 1: Intro + Dermatophytes Flashcards

1
Q

Saprophytic fungi

A

Live on dead or decayed organic matter in the environment

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2
Q

T/F: Fungal infections are generally communicable via person-to-person.

A

FALSE
Humans are often accidental hosts via inhalation of spores or introduction of fungi to tissue

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3
Q

Unicellular fungi that develop moist, creamy, opaque, or pasty colonies

A

Yeast

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4
Q

Multicellular fungi that demonstrate fluffy, cottony, wooly, or powdery colonies

A

Filamentous fungi/molds

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5
Q

Theramally Dimorphic fungi (what are they and what temps are they at which stage)

A

Dimorphic fungi exhibit a yeast and filamentous phase dependent upon temperature
Mold = cold
Yeast = body temp (warm)

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6
Q

Polymorphic fungi

A

Fungi with more than one independent form or spore stage in their life cycle, not temperature dependent
(ex. Candida species –> yeast forms, pseudohyphae, and/or true hyphae)

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7
Q

What 5 characteristics do MOST fungi share?

A
  • Chitin in cell wall
  • Ergosterol in cell membrane
  • Reproduction by means of spores
  • Lack of chlorophyll
  • Lack of susceptibility to antibacterial antibiotics
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8
Q

Zygomycota

A
  • Produce aseptate or sparsely septate hyphae
  • Asexual reproduction by sporangiospores
  • Sexual reproduction by zygospores
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9
Q

Ascomycota

A
  • Reproduce asexually by forming conidia
  • Reproduce sexually by forming ascospores
  • Produce true septate hyphae
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10
Q

Basidiomycota

A
  • Reproduce sexually by forming basidiospores on a structure called basidia
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11
Q

What are the 4 clinical categories of fungi?

A
  • Superficial (cutaneous mycoses)
  • Subcutaneous mycoses
  • Systemic mycoses
  • Opportunistic mycoses
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12
Q

Superficial mycoses

A

Involve keratinized tissue (hair, skin, nails) with no invasion of deeper tissue

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13
Q

Subcutaneous mycoses

A

Confined to subcutaneous tissue without dissemination to distant sites

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14
Q

Systemic mycoses

A

Widely disseminated infections that can involve any organ system, mostly involving lungs

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15
Q

Opportunistic mycoses

A

Any fungi can be opportunistic, associated with immunocompromised patients

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16
Q

Dematiaceous vs hyaline

A

Hyaline = nonpigmented
Dematiaceous = melanized (dark pigment)

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17
Q

Virulence factors of opportunistic fungi

A
  • Size (smaller = more likely to infect)
  • Ability to grow at 37C at neutral pH
  • Conversion of mold to yeast in host
  • Toxin production
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18
Q

Mold cultures and clinical specimens MUST be handled in a class ___ BSC.
Yeast specimens can be handled _________

A

II
Yeast = can be handled on bench top

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19
Q

What is suitable for decontamination of molds?

A

Electric incinerator

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20
Q

Cultures of pathogenic organisms should be _____________

A

sealed with tape/parafilm

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21
Q

Once definitive ID is made, how to dispose?

A

Via autoclave

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22
Q

Fungal specimens should be processed within ____ hours of receipt.

A

2

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23
Q

What is the most common specimens collected for fungal culture?

A

Lower respiratory tract specimens

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24
Q

Lower respiratory tract fungal specimen storage requirements

A

Stored @ RT if processed within 2 hours
Refrigerated if delayed

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25
Q

Sterile body fluid fungal cultures are collected in ________ and a minimum of ____ mL is required.

A

Heparin blood tubes
2 mL

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26
Q

Sterile body fluid fungal specimen storage requirements

A

Should be processed ASAP
Store at RT, NEVER refrigerate!

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27
Q

Fungal eye specimens, storage requirements and how are they plated

A

Plated on noninhibitory media in an X or C shaped pattern
Stored at RT, do not refrigerate

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28
Q

Hair/skin/nail scrapings storage requirements

A

NEVER refrigerate
Incubation for at least 21 days at 30C before reporting as negative

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29
Q

Vaginal fungal specimens transport/storage requirements

A

Must be transported within 24 hours
Kept moist –> suitable for wet prep
Screened for yeasts using chromogenic agars for Candida spp.

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30
Q

Urine fungal specimens transport/storage requirements

A

Samples centrifuged and sediment cultured
Stored at RT if within 2 hours
Refrigerate if delayed
If transport system used, room temp for up to 72hrs

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31
Q

Tissue fungal specimens

A

Minced before culturing
Cultures incubated for 21 days at 30C

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32
Q

Cycloheximide

A

Inhibits pathogenic fungi
If media with cycloheximide is used, media without cycloheximide should also be used

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33
Q

What is BHI agar used for?

A

Primary recovery of saprobic and pathogenic fungi (grows bacteria, yeast, and pathogenic fungi)

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34
Q

What is Chromogenic agar used for?

A

Isolation and presumptive ID of yeast and filamentous fungi

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35
Q

What is inhibitory mold (IMA) agar used for?

A

Primary recovery of pathogenic, cycloheximide sensitive fungi exclusive of dermatophytes

  • Contains chloramphenicol to inhibit bacterial growth
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36
Q

What is mycosel agar used for?

A

Primary recovery of dermatophytes - inhibits bacteria and saprophytic fungi

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37
Q

What is Sabouraud dextrose agar used for?

A

Primary recover of saprobic and pathogenic fungi - grows all fungi

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38
Q

What color will C. tropicalis be on CHROMagar?

A

Metallic blue

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39
Q

What color will C. krusei be on CHROMagar?

A

Pink, fuzzy

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40
Q

What color will C. albicans be on CHROMagar?

A

Green

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41
Q

What color will C. glabrata be on CHROMagar?

A

Mauve

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42
Q

What is india ink stain used for? What does a positive result look like?

A

Detection of Cryptococcus sp. in CSF
Cryptococcus sp. will have a halo around the yeast against a dark background

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43
Q

What is lactophenol cotton blue wet mount used for?

A

Most widely used method of staining and observing fungi

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44
Q

What is calcofluor white stain used for?

A

Detection of fungi

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45
Q

What is KOH used for?

A

Clearing of specimen to make fungi more readily visible, used for direct wet mount of specimens

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46
Q

What stains bind to polysaccharides, chitin, and cellulose present in fungi?

A

Calcofluor white and lactophenol blue stains

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47
Q

What does lactophenol blue stain contain and what does it do?

A

Lactic acid –> preserves fungal structures
Phenol –> Acts as a killing agent
Cotton blue –> stains fungal wall

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48
Q

What is a polysaccharide that is present in the cell wall of some fungi?

A

(1,3)-B-D-Glucan

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49
Q

What is the “gold standard” for identifying fungi?

A

Microscopic morphological features

50
Q

Slow growers vs intermediate growers vs rapid growers

A

Slow = mature colonies in 11-21 days
Intermediate = mature colonies in 6-10 days
Rapid = mature colonies <5 days

51
Q

Verrucose

A

Furrowed or convoluted

52
Q

Umbonate

A

Slightly raised in the center

53
Q

Rugose

A

Furrows radiate from the center

54
Q

Cottony

A

loose, high aerial mycelium

55
Q

Velvety

A

Low aerial mycelium resembling velvet cloth

56
Q

Glabrous

A

Smooth surface with no aerial mycelium

57
Q

Granular

A

Dense, powdery, resembling sugar granules

58
Q

Wooly

A

high aerial mycelium that appears slightly matted down

59
Q

Definitive ID of fungi via microscopic morphological features is based on ?

A

Shape, method of reproduction, and arrangement of spores

60
Q

Each of the branching filaments that make up the mycelium of a fungus

61
Q

Curved, freely branching, have the appearance of antlers

A

Antler hyphae (AKA favic chandelier)

62
Q

Enlarged, club-shaped structures

A

Racquet hyphae

63
Q

Coiled or exhibit corkscrewlike turns in the hyphal strand

A

Spiral hyphae

64
Q

A network of fungal threads or hyphae

65
Q

Play a role in the reproduction of fungus (upward facing)

66
Q

Play a role in nutrients and energy metabolism (downward facing)

A

Vegetative

67
Q

True hyphae

A

Consist of long tubes with parallel sides and no constrictions

68
Q

Pseudohyphae

A

Consist of chains of cells that show a constriction between adjacent cells

69
Q

Septate hyphae

A

Hyphae with walls (septa) between cells

70
Q

Aseptate hyphae

A

Hyphae that lack walls between cells

71
Q

What microscopic structures are associated with sexual reproduction?

A

Ascocarp - saclike structures that contain smaller sacs (asci) which each contain 4-8 ascospores, not commonly seen

72
Q

What microscopic structures are associated with asexual reproduction?

A

Conidia, arthroconidia, chlamydococonidia

73
Q

Intercalary vs terminal

A

Intercalary: within the hyphae
Terminal: on the end of the hyphae

74
Q

What do echinocandins do?

A

Inhibit synthesis of B-1,3-D-glucan in fungi (damage of fungal cell wall)

75
Q

4 main classes of antifungals

A

Azoles
Polyenes (Amphotericin-B)
Allylamines (Terbinafine)
Echinocandins (Caspofungin)

76
Q

Ergosterol

A

Fungal version of cholesterol, predominant component of the fungal cell membrane
Regulates membrane fluidity and integrity in fungal cells

77
Q

B-1,3-D-glucan

A

Predominant component of the inner layer of the fungal cell wall
Great target for antifungals because not found elsewhere in nature

78
Q

What are the ergosterol inhibitors/binders?

A

Azoles, polyenes, allylamines

79
Q

Role of Azoles as an antifungal

A

Inhibit a fungal cytochrome P450

80
Q

Role of polyenes as an antifungal

A

Form pores in cell membrane

81
Q

Role of allylamines as an antifungal

A

Accumulates squalene

82
Q

Dermatomycoses

A

Fungal infections involving
the superficial areas of the body including the hair, skin, and nails

83
Q

What are the 3 genera of dermatophytes?

A

Trichophyton
Microsporum
Epidermophyton

84
Q

Dermatophytes break down and utilize _________ as a source of nitrogen

85
Q

Trichophyton infects:

A

hair, skin, nails

86
Q

Microsporum infects:

A

hair and skin only

87
Q

Epidermophyton infects:

A

skin and nails only

88
Q

Cutaneous mycoses are usually referred to as _______. aka “__________”

A

tinea; ringworm

89
Q

What are the most common fungal infections of humans?

A

Cutaneous mycoses

90
Q

Tinea corporis

A

Ringworm of the body

91
Q

Tinea cruris

A

Ringworm of the groin AKA jock itch

92
Q

Tinea capitis

A

Ringworm of the scalp and hair

93
Q

Tinea barbae

A

Ringworm of the beard AKA barbers itch

94
Q

Tinea unguium

A

Ringworm of the nail

95
Q

Tinea pedia

A

Ringworm of the feet AKA athlete’s foot

96
Q

What species is the most important and common causes of infections of the feet and nails?

A

Trichophyton spp.

97
Q

Anthropophilic

A

Human loving

98
Q

Zoophilic

A

Primarily infect animals

99
Q

Geophilic

A

Soil associated

100
Q

Endothrix vs ectothrix infection

A

Endothrix - masses of spores INSIDE the hair shaft
Ectothrix - masses of spores ON the hair shaft

101
Q

How do you determine if an infection is endothrix or ectothrix?

A

Hair Perforation Test

102
Q

Name the dermatophytes that fluoresce under Wood’s Lamp and the color:

A

Microsporum audouinii –> bright green/yellow
Microsporum canis –> bright green/yellow
Trichophyton schoenleinii –> pale green/yellow

103
Q

What are the two most common Trichophyton species found in the clinical lab?

A

T. rubrum
T. mentagrophytes complex

104
Q

Describe microconidia and macroconidia of Trichophyton spp.

A

Macroconidia - club shaped/cigar shaped
Microconidia - teardrop shaped/birds on a fence morphology

105
Q

Describe STANDOUT features of T. rubrum

A
  • Characteristic cherry red colony (underside)
  • Does NOT perforate hair
  • Slow growing
  • Does NOT produce urease
106
Q

Describe STANDOUT features of T. mentagrophytes

A
  • Perforates hair!
  • Rapid grower
  • Produces urease
  • Rose/brown underside colony
107
Q

Describe STANDOUT features of T. tonsurans

A
  • Causes epidemic form of tinea capitis in children (primary cause of tinea capitis in most of US)
  • Associated with alopecia
  • Endothrix infection
  • Slow grower
  • BALLOON FORM microconidia
108
Q

Describe STANDOUT features of T. verrucosum

A
  • Causes lesions in cattle and humans, associated with farmers
  • BOTH endothrix and ectothrix
  • Slow grower
  • ANTLER HYPHAE
  • RAT TAIL/STRING BEAN appearance macroconidia
109
Q

Describe STANDOUT features of T. schoenleinii

A
  • Scarring form of tinea capitis called favus
  • Spread between family members
  • Endothrix infection
  • FAVIC CHANDELIER hyphae
110
Q

Describe STANDOUT features of T. violaceum

A
  • Endothrix infection
  • Typical “black dot” type of tinea capitis
  • Colony = PORT WINE color
111
Q

Microsporum spp have easily recognizable macroconidia. Describe the STANDOUT features of their macroconidia

A

Echinulate (covered with small spines)
Spindle-shaped
Rough-walled
Contain 4 or more septa (except M. nanum)

112
Q

Describe STANDOUT features of M. audouinii

A
  • Epidemic tinea capitis in school children
  • Anthropophilic
  • Ectothrix growth
  • Transmission by infected hats/combs
  • SALMON PINK underside colony
  • Fluorescence under Wood’s lamp
113
Q

Describe STANDOUT features of M. canis

A
  • Zoophilic
  • Most common cause of ringworm in dogs and cats in the US
  • Fluorescence under Wood’s lamp
  • Ectothrix growth
  • Rapid growers
  • Bright yellow underside
  • Many spindle shaped/echinulate macroconidia
114
Q

Describe STANDOUT features of M. gypseum

A
  • Geophilic
  • Ectothrix growth
  • Rarely cause human or animal infections
  • Cinnamon colored colonies
  • Macroconidia seen in large numbers
115
Q

Describe STANDOUT features of Epidermophyton spp. (E. floccosum)

A
  • Causes tinea cruris and tinea pedis
  • Susceptible to cold
  • Olive green to khaki colored colonies
  • NO microconidia
  • Numerous macroconidia (may be seen in groups of 2 or 3 on conidiophore)
116
Q

Describe STANDOUT features of Malassezia spp.

A
  • Basidiomycota group (reproduce sexually)
  • Lipophilic
  • Cause superficial skin diseases (tinea versicolor, pityriasis versicolor)
117
Q

M. furfur STANDOUT features

A
  • Causes tinea versicolor
  • Growth must be stimulated by natural oils (most common method = Sabdex overlaid with olive oil)
  • Microscopic: spaghetti and meatballs morphology
118
Q

Hortaea werneckii STANDOUT features

A
  • Halophilic
  • Dematiaceous (black underside colony)
  • Causes tinea nigra
  • Young colonies produce annelides
119
Q

Annelides

A

Pale or dark brown yeast-like cells

120
Q

Trichosporon spp. STANDOUT features

A
  • C. asahii most common species isolated
  • Associated with disease in immunocompromised patients
  • Causes white piedra
  • Numerous round to rectangular arthroconidia
  • POSITIVE UREASE PRODUCTION
121
Q

Piedraia hortae STANDOUT features

A
  • Causes black piedra
  • Dematiaceous
  • Many intercalary chlamydoconidium-like cells
  • Asci may be produced (whiplike extensions)

Microbiology (24 decks)

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