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Flashcards in Fungi Deck (81):
1

Basic character of fungi

Mold or yeast forms

2

Cell type of fungi

Eukaryotic with outer wall and cell membrane

3

Classification of fungi

spores; typical disease caused

4

Cell wall of fungi

Rigid composed of chitin and glucan

5

Cell/particle membrane of fungi

Cell membrane has ergosterol instead of cholesterol

6

Reproduction of fungi

Sexual and/or asexual; spores; yeast budding

7

Coencytic hyphae

Hyphae with no septa

8

Septate hyphae

Hyphae with septa

9

Mycelium

Vegetative part of a fungus that is network of hyphae (mold)

10

Fruiting bodies

Macroconidia (with released conidia spores)
Endospores (conidia enclosed in a sporangium sac)

11

Yeasts fungal growth and morphology

Unicellular; reproduce - asexually by budding (blastoconidia) or sexually by fusion; growth on solid culture plates resembles bacterial colonies; most fungal pathogens can grow as yeast in the body

12

Molds fungal growth and morphology

Multicellular, grow as long, tube-like extensions of the cell wall; hyphae

13

What infection is associated with mycelia?

Mycetoma infection - chronic infection of skin and subcutaneous tissue (causes masses underneath the skin)

14

Reproductive structures of mold

Asexual: conidia and arthroconidia
Sexual: ascospores and basidiospores

15

Conidia

Produced by budding

16

Arthroconidia

Hyphal segments fragment into individual cells

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Ascospores

produced in ascus sac

18

Basidiospores

produced in basidium

19

Dimorphism

Ability of a fungus to grow as a yeast or a mold depending on environmental conditions; dimorphic pathogens generally grow as yeasts at body temp (37C), molds in their natural soil environment (25C)

20

Superficial mycoses

Colonize outermost layers (keratinized) of skin, nails, and hair

21

Malassezia furfur labs and morphology

Spaghetti and meatball organization; KOH, calcofluor, PAS, standard medium with olive oil (cream)

22

Pityriasis (tinea) versicolor

hypo/hyperpigmented, irregular, well-demarcated macules (can be raised or scaled); predisposing factors - folliculitis, dacryocystitis (infection of lacrimal sac)

23

Hortaea (exophiala) werneckii labs and morphology

Black fungus, dematiaceous, branched hyphae, arthroconidia and elongate budding cells; KOH, H&E, sabouraud dextrose agar media = black mold

24

Tinea nigra

Palms and soles; solitary, irregular pigmented macule, no scaling or invasion into hair follicles; asymptomatic

25

Malassazeia furfur clinical disease

Pitariasis (tinea) versicolor

26

Hortaea (exophiala) werneckii clinical disease

Tinea nigra

27

Hortaea (exophiala) werneckii epidemiology

-Less than 1% of fungal infections
-(Sub)tropical
-children and young adults
-trauma in dermis
-associated with water

28

Tricosporon spp. cause...

White piedra

29

Trichosporon spp. morphology and lab

-Hyaline septate hyphae
-Arthroconidia and some blastoconidia
-Standard medium - cream-colored colonies

30

Piedraia hortae causes...

Black piedra

31

Piedraia hortae morphology and lab

-Spindle-shaped ascospores within asci
-Branched, pigmented hyphae
-standard medium - velvety

32

White piedra

-Groin, axillary, and less commonly scalp hair involved
-hair stem covered with white fungus
-no damage to hair shaft

33

Black piedra

Small, dark nodules on hair shaft (mostly involve the scalp)

34

Cutaneous mycoses clinical disease

Cause dermatophytosis (tinea, ringworm)

35

Symptomatic infections of cutaneous mycoses

Invasion of skin (corneum), hair, and nails (keratinized layers too)

36

Morphology of cutaneous mycoses

-Hyaline (translucent) septate hyphae
-Macroconidia vs micro help in identification

37

Hair infection where arthroconidia form on outside of hair

Ectothrix

38

Hair infection where arthroconidia form in inside of hair

Endothrix

39

Hair infection where hyphae, arthroconidia, form in empty spaces of hair (air bubble appearance)

Favic

40

Major symptoms of cutaneous mycoses

Itching
↑ inflammation – contracted from animals
↓ inflammation – contracted from human

41

Tricophyton spp. cause which diseases...

-Tinea pedis
-Tinea corporis
-Tinea cruris
-Tinea capitis
-Tinea barbae
-Tinea unguium

42

Epidermophyton floccosum cause which diseases...

-Tinea pedis
-Tinea cruris
-Tinea unguium

43

Microsporum spp. cause which diseases...

-Tinea corporis
-Tinea capitis

44

How can cutaneous mycoses be identified in general?

By microscopy (aided by KOH and stain)

45

Tinea corporis

Ringworm of trunk and legs

46

Tinea pedia

Athlete's foot

47

Tinea capitis

Scalp, eyebrows, lashes ringworm

48

Tinea barbae

Ringworm of the beard

49

Tinea unguium

Onychomycosis (nail infection)

50

Fruiting bodies of microsporum canis

-Macroconidia
-rough-walled, spindle-shaped (ends pointed)

51

Fruiting bodies of trichophyton mentagrophytes

-Macroconidia
-short, thin-walled, cigar-shaped (ends rounded)

52

Fruiting bodies of trichophyton rubrum

-Macroconidia
-Long, narrow, thin-walled pencil shape

53

Fruiting bodies of epidermophyton floccosum

-Macroconidia
-Smooth-walled, club-shaped

54

Sporothrix schenckii morphology

-Ubiquitous in soil
-Dimorphic fungus
-Room temp – Mold
-37°C – pleomorphic yeast

55

Sporothrix schenckii mold phase morphology

-Septate hyphae
-Oval conidia
-Conidiophore (stalk that carries conidia) rosette-shaped

56

Sporothrix schenckii yeast phase morphology

Cigar-shaped bud

57

Sporothrix schenckii epidemiology

-Japan, North America, and South America - warmer climates
-Most common in individuals who work outside (gardeners)
-trauma (finger prick, cut)
-Cats and armadillo – zoonotic transmission

58

Sporothrix schenckii disease

Sporotrichosis

59

Sporothrix schenckii labs

-Culture is gold standard (SDA) and associated morphology
-Appearance of Splendore-Hoeppli material in H&E (asteroid body)

60

Sporotrichosis

-Primary nodule site presents as small nodule that may ulcerate
-Secondary nodules present as a linear chain of painless subcutaneous nodules
-Spread along lymphatic drainage
-Nodules may ulcerate with pus discharge

61

Chromoblastomycosis epidemiology

-Rural areas of tropics
-Involves legs and arms
-In the Americas – F. pedrosoi – lower extremities
-In Australia – C. carrionii – upper extremities

62

Chromoblastomycosis biology and morphology of causative fungi

-All species are dematiaceous (pigmented) molds
-Morphologically diverse
-In tissue, all spp form muriform cells (sclerotic bodies)
-Chestnut brown due to melanin in cell wall
-Divide by internal septation – cells have vertical and horizontal lines
-Pigmented hyphae may be seen

63

Chromoblastomycosis

-Chronic infection of skin and subcutaneous tissue; pruritic
Indolent (slow) growing verrucous nodules/plaques
-Presentation indicates a well-established infection
-Early lesions:
-Small, warty papules that grow slowly
-Established infection:
-Multiple, large cauliflower-like growths
-Hyperkeratotic lesions and fibrosis
-Complications
-Squamous cell carcinoma
-Bacterial infection

64

Chromoblastomycosis labs

-Scrapings from lesions
-Microscopy (Muriform** cells)
-20% KOH treatment
-Biopsy – H&E
-Cayenne pepper appearance of lesions**
-Fungal cultures
-Slow-growing colonies
-Dark pigments
-Velvety appearance

65

Mycetoma epidemiology

-Predominant in tropics with low rainfall
-Africa, India, Brazil, Middle East
-Usually enters body through traumatic implantation**
-Foot** most common location

66

Mycetoma general biology and morphology

-Result in granuloma formation that contain hyphae aggregates termed granules or grains**
-Dematiaceous (black grain) or hyaline (pale or white grain)
-Septate and branching hyphae** may be embedded in cement-like coating
-Splendore-Hoeppli material present

67

Mycetoma chronic disease

-Clinical Triad: tumor, sinus tracts, granules
-Early lesions:
-Small, painless, subcutaneous nodules/plaques
-Established infection:
-Granulomas enlarge and sinus tracts form on surface
-Serosanguineous fluid drainage (can send to lab)
-Muscle and bone destruction – deformations

68

Mycetoma complications

S. aureus infection

69

Mycetoma immune reaction

Pseudoepitheliomatous hyperplasia
-Hyperplasia (increased cell production) of the epidermis
-Chronic inflammation
-Generally benign

70

Mycetoma labs

-Scrapings from lesions
-Microscopy (septate, branching hyphae with large swollen cells on edge)
-20% KOH treatment
-Gram stain to eliminate bacterial infection
-Histopathology
-H&E stain
-Fungal cultures
-RT and 37°C for six to eight weeks

71

Candida spp.

Opportunistic pathogen, yeast; normal commensal in human GI, vaginal tract, and skin

72

Candida transmission

-Endogenous – involves commensals on self
-Exogenous – hospital acquired

73

Candida morphology

-Oval yeast-like cells that produce buds (blastoconidia) and chlamydospores
-Produce pseudohyphae** and hyphae
-C. albicans forms germ-tubes**

74

Candida virulence factors and pathogenesis

-Adherence – Hyphal Wall Protein (attachment protein to epithelial cells)
-Proteinases – hydrolyze host proteins (collagen and fibronectin) that are involved with host protection
-Phospholipases – lecithinase that cleaves fatty acids from glycerol backbone of membrane phospholipids
-Phenotypic switching** – expression of cell wall glycoproteins, proteolytic enzyme secretion, decreased susceptibility to oxidative damage by neutrophils

75

Candida diseases

Cutaneous candidiasis**, diaper dermatitis**, paronychia**, perianal candidiasis, balanitis (balanoposthitis if prepuce), chronic mucocutaneous candidiasis

76

Cutaneous candidiasis

-Develops in folds of skin (intertrigo); armpits, groin, between fingers, and under the breasts
-Warm, moist environments

77

Diaper dermatitis

-Secondary infection after bacterial infection
-Beefy red plaques, satellite papules, and pustules

78

Paronychia

Nail-skin interface

79

Predisposing factors to candidiasis

-Immunosuppression (drug-induced, AIDS)
-Neutropenia (WBC < 500/mm3)**
-Burn victims
-Assisted ventilation, indwelling catheters
-Diabetics – high glucose impairs neutrophil function
-Broad-spectrum antibiotic use

80

Candida labs

KOH with calcofluor, PAS, GMS, Gram stain**
Cultures: smooth, white, creamy, domed colonies
Germ tube test:
-Cells incubated in serum for a few hours at 37C
-A slender structure protrudes out or cell (looks like a comma)

81

Tinea cruris

Jock itch