Mycology Exam 1: Intro + Dermatophytes Flashcards
1
Q
Saprophytic fungi
A
Live on dead or decayed organic matter in the environment
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
3
Q
Unicellular fungi that develop moist, creamy, opaque, or pasty colonies
A
Yeast
4
Q
Multicellular fungi that demonstrate fluffy, cottony, wooly, or powdery colonies
A
Filamentous fungi/molds
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)
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)
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
8
Q
Zygomycota
A
- Produce aseptate or sparsely septate hyphae
- Asexual reproduction by sporangiospores
- Sexual reproduction by zygospores
9
Q
Ascomycota
A
- Reproduce asexually by forming conidia
- Reproduce sexually by forming ascospores
- Produce true septate hyphae
10
Q
Basidiomycota
A
- Reproduce sexually by forming basidiospores on a structure called basidia
11
Q
What are the 4 clinical categories of fungi?
A
- Superficial (cutaneous mycoses)
- Subcutaneous mycoses
- Systemic mycoses
- Opportunistic mycoses
12
Q
Superficial mycoses
A
Involve keratinized tissue (hair, skin, nails) with no invasion of deeper tissue
13
Q
Subcutaneous mycoses
A
Confined to subcutaneous tissue without dissemination to distant sites
14
Q
Systemic mycoses
A
Widely disseminated infections that can involve any organ system, mostly involving lungs
15
Q
Opportunistic mycoses
A
Any fungi can be opportunistic, associated with immunocompromised patients
16
Q
Dematiaceous vs hyaline
A
Hyaline = nonpigmented
Dematiaceous = melanized (dark pigment)
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
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
19
Q
What is suitable for decontamination of molds?
A
Electric incinerator
20
Q
Cultures of pathogenic organisms should be _____________
A
sealed with tape/parafilm
21
Q
Once definitive ID is made, how to dispose?
A
Via autoclave
22
Q
Fungal specimens should be processed within ____ hours of receipt.
A
2
23
Q
What is the most common specimens collected for fungal culture?
A
Lower respiratory tract specimens
24
Q
Lower respiratory tract fungal specimen storage requirements
A
Stored @ RT if processed within 2 hours
Refrigerated if delayed
25
Sterile body fluid fungal cultures are collected in ________ and a minimum of ____ mL is required.
Heparin blood tubes
2 mL
26
Sterile body fluid fungal specimen storage requirements
Should be processed ASAP
Store at RT, NEVER refrigerate!
27
Fungal eye specimens, storage requirements and how are they plated
Plated on noninhibitory media in an X or C shaped pattern
Stored at RT, do not refrigerate
28
Hair/skin/nail scrapings storage requirements
NEVER refrigerate
Incubation for at least 21 days at 30C before reporting as negative
29
Vaginal fungal specimens transport/storage requirements
Must be transported within 24 hours
Kept moist --> suitable for wet prep
Screened for yeasts using chromogenic agars for Candida spp.
30
Urine fungal specimens transport/storage requirements
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
31
Tissue fungal specimens
Minced before culturing
Cultures incubated for 21 days at 30C
32
Cycloheximide
Inhibits pathogenic fungi
If media with cycloheximide is used, media without cycloheximide should also be used
33
What is BHI agar used for?
Primary recovery of saprobic and pathogenic fungi (grows bacteria, yeast, and pathogenic fungi)
34
What is Chromogenic agar used for?
Isolation and presumptive ID of yeast and filamentous fungi
35
What is inhibitory mold (IMA) agar used for?
Primary recovery of pathogenic, cycloheximide sensitive fungi exclusive of dermatophytes
- Contains chloramphenicol to inhibit bacterial growth
36
What is mycosel agar used for?
Primary recovery of dermatophytes - inhibits bacteria and saprophytic fungi
37
What is Sabouraud dextrose agar used for?
Primary recover of saprobic and pathogenic fungi - grows all fungi
38
What color will C. tropicalis be on CHROMagar?
Metallic blue
39
What color will C. krusei be on CHROMagar?
Pink, fuzzy
40
What color will C. albicans be on CHROMagar?
Green
41
What color will C. glabrata be on CHROMagar?
Mauve
42
What is india ink stain used for? What does a positive result look like?
Detection of Cryptococcus sp. in CSF
Cryptococcus sp. will have a halo around the yeast against a dark background
43
What is lactophenol cotton blue wet mount used for?
Most widely used method of staining and observing fungi
44
What is calcofluor white stain used for?
Detection of fungi
45
What is KOH used for?
Clearing of specimen to make fungi more readily visible, used for direct wet mount of specimens
46
What stains bind to polysaccharides, chitin, and cellulose present in fungi?
Calcofluor white and lactophenol blue stains
47
What does lactophenol blue stain contain and what does it do?
Lactic acid --> preserves fungal structures
Phenol --> Acts as a killing agent
Cotton blue --> stains fungal wall
48
What is a polysaccharide that is present in the cell wall of some fungi?
(1,3)-B-D-Glucan
49
What is the "gold standard" for identifying fungi?
Microscopic morphological features
50
Slow growers vs intermediate growers vs rapid growers
Slow = mature colonies in 11-21 days
Intermediate = mature colonies in 6-10 days
Rapid = mature colonies <5 days
51
Verrucose
Furrowed or convoluted
52
Umbonate
Slightly raised in the center
53
Rugose
Furrows radiate from the center
54
Cottony
loose, high aerial mycelium
55
Velvety
Low aerial mycelium resembling velvet cloth
56
Glabrous
Smooth surface with no aerial mycelium
57
Granular
Dense, powdery, resembling sugar granules
58
Wooly
high aerial mycelium that appears slightly matted down
59
Definitive ID of fungi via microscopic morphological features is based on ?
Shape, method of reproduction, and arrangement of spores
60
Each of the branching filaments that make up the mycelium of a fungus
Hyphae
61
Curved, freely branching, have the appearance of antlers
Antler hyphae (AKA favic chandelier)
62
Enlarged, club-shaped structures
Racquet hyphae
63
Coiled or exhibit corkscrewlike turns in the hyphal strand
Spiral hyphae
64
A network of fungal threads or hyphae
Mycelium
65
Play a role in the reproduction of fungus (upward facing)
Aerial
66
Play a role in nutrients and energy metabolism (downward facing)
Vegetative
67
True hyphae
Consist of long tubes with parallel sides and no constrictions
68
Pseudohyphae
Consist of chains of cells that show a constriction between adjacent cells
69
Septate hyphae
Hyphae with walls (septa) between cells
70
Aseptate hyphae
Hyphae that lack walls between cells
71
What microscopic structures are associated with sexual reproduction?
Ascocarp - saclike structures that contain smaller sacs (asci) which each contain 4-8 ascospores, not commonly seen
72
What microscopic structures are associated with asexual reproduction?
Conidia, arthroconidia, chlamydococonidia
73
Intercalary vs terminal
Intercalary: within the hyphae
Terminal: on the end of the hyphae
74
What do echinocandins do?
Inhibit synthesis of B-1,3-D-glucan in fungi (damage of fungal cell wall)
75
4 main classes of antifungals
Azoles
Polyenes (Amphotericin-B)
Allylamines (Terbinafine)
Echinocandins (Caspofungin)
76
Ergosterol
Fungal version of cholesterol, predominant component of the fungal cell membrane
Regulates membrane fluidity and integrity in fungal cells
77
B-1,3-D-glucan
Predominant component of the inner layer of the fungal cell wall
Great target for antifungals because not found elsewhere in nature
78
What are the ergosterol inhibitors/binders?
Azoles, polyenes, allylamines
79
Role of Azoles as an antifungal
Inhibit a fungal cytochrome P450
80
Role of polyenes as an antifungal
Form pores in cell membrane
81
Role of allylamines as an antifungal
Accumulates squalene
82
Dermatomycoses
Fungal infections involving
the superficial areas of the body including the hair, skin, and nails
83
What are the 3 genera of dermatophytes?
Trichophyton
Microsporum
Epidermophyton
84
Dermatophytes break down and utilize _________ as a source of nitrogen
Keratin
85
Trichophyton infects:
hair, skin, nails
86
Microsporum infects:
hair and skin only
87
Epidermophyton infects:
skin and nails only
88
Cutaneous mycoses are usually referred to as _______. aka "__________"
tinea; ringworm
89
What are the most common fungal infections of humans?
Cutaneous mycoses
90
Tinea corporis
Ringworm of the body
91
Tinea cruris
Ringworm of the groin AKA jock itch
92
Tinea capitis
Ringworm of the scalp and hair
93
Tinea barbae
Ringworm of the beard AKA barbers itch
94
Tinea unguium
Ringworm of the nail
95
Tinea pedia
Ringworm of the feet AKA athlete's foot
96
What species is the most important and common causes of infections of the feet and nails?
Trichophyton spp.
97
Anthropophilic
Human loving
98
Zoophilic
Primarily infect animals
99
Geophilic
Soil associated
100
Endothrix vs ectothrix infection
Endothrix - masses of spores INSIDE the hair shaft
Ectothrix - masses of spores ON the hair shaft
101
How do you determine if an infection is endothrix or ectothrix?
Hair Perforation Test
102
Name the dermatophytes that fluoresce under Wood's Lamp and the color:
Microsporum audouinii --> bright green/yellow
Microsporum canis --> bright green/yellow
Trichophyton schoenleinii --> pale green/yellow
103
What are the two most common Trichophyton species found in the clinical lab?
T. rubrum
T. mentagrophytes complex
104
Describe microconidia and macroconidia of Trichophyton spp.
Macroconidia - club shaped/cigar shaped
Microconidia - teardrop shaped/birds on a fence morphology
105
Describe STANDOUT features of T. rubrum
- Characteristic cherry red colony (underside)
- Does NOT perforate hair
- Slow growing
- Does NOT produce urease
106
Describe STANDOUT features of T. mentagrophytes
- Perforates hair!
- Rapid grower
- Produces urease
- Rose/brown underside colony
107
Describe STANDOUT features of T. tonsurans
- 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
Describe STANDOUT features of T. verrucosum
- Causes lesions in cattle and humans, associated with farmers
- BOTH endothrix and ectothrix
- Slow grower
- ANTLER HYPHAE
- RAT TAIL/STRING BEAN appearance macroconidia
109
Describe STANDOUT features of T. schoenleinii
- Scarring form of tinea capitis called favus
- Spread between family members
- Endothrix infection
- FAVIC CHANDELIER hyphae
110
Describe STANDOUT features of T. violaceum
- Endothrix infection
- Typical "black dot" type of tinea capitis
- Colony = PORT WINE color
111
Microsporum spp have easily recognizable macroconidia. Describe the STANDOUT features of their macroconidia
Echinulate (covered with small spines)
Spindle-shaped
Rough-walled
Contain 4 or more septa (except M. nanum)
112
Describe STANDOUT features of M. audouinii
- Epidemic tinea capitis in school children
- Anthropophilic
- Ectothrix growth
- Transmission by infected hats/combs
- SALMON PINK underside colony
- Fluorescence under Wood's lamp
113
Describe STANDOUT features of M. canis
- 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
Describe STANDOUT features of M. gypseum
- Geophilic
- Ectothrix growth
- Rarely cause human or animal infections
- Cinnamon colored colonies
- Macroconidia seen in large numbers
115
Describe STANDOUT features of Epidermophyton spp. (E. floccosum)
- 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
Describe STANDOUT features of Malassezia spp.
- Basidiomycota group (reproduce sexually)
- Lipophilic
- Cause superficial skin diseases (tinea versicolor, pityriasis versicolor)
117
M. furfur STANDOUT features
- Causes tinea versicolor
- Growth must be stimulated by natural oils (most common method = Sabdex overlaid with olive oil)
- Microscopic: spaghetti and meatballs morphology
118
Hortaea werneckii STANDOUT features
- Halophilic
- Dematiaceous (black underside colony)
- Causes tinea nigra
- Young colonies produce annelides
119
Annelides
Pale or dark brown yeast-like cells
120
Trichosporon spp. STANDOUT features
- C. asahii most common species isolated
- Associated with disease in immunocompromised patients
- Causes white piedra
- Numerous round to rectangular arthroconidia
- POSITIVE UREASE PRODUCTION
121
Piedraia hortae STANDOUT features
- Causes black piedra
- Dematiaceous
- Many intercalary chlamydoconidium-like cells
- Asci may be produced (whiplike extensions)
