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Microbiology test 3 > Dermatomycoses & Ectoparasitic Infections (session 23) > Flashcards

Dermatomycoses & Ectoparasitic Infections (session 23) Flashcards

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Biology 101 flashcards
1
Q

(C) beard ringworm

A

Tinea barbae

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2
Q

(C) scalp ringworm

A

Tinea capitis

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3
Q

(C) arm, leg, torso ringwork

A

Tinea corporis

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4
Q

(C) groin ringworm

A

Tinea crurus

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5
Q

(C) hand ringworm

A

Tinea manus

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6
Q

(C) food ringworm

A

Tinea pedis

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7
Q

(C) nail ringworm

A

Tinea unguium

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8
Q

Dermatophyte morphology

A

hyphae & arthoconidia can be visualized in dead keratinized tissue

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9
Q

What do dermatophytes secrete and why?

A

dermatophytes secrete keratinase which allows for inhabiting keratinized regions of the body

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10
Q

Important general of dermatophytes (3) & 2 other cutaneous forms

A 
Imp. Genera
Epidermophyton
Microsporum
Trichophyton
Other cutaneous forms:
Malassezia furfur
Hartaea werneckii
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11
Q

2 environmental dermatophytes with sexual spores

A

Microsporum

Trichophyton

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12
Q

Dermatophytes lab culture & dx

A
  • culture material under nails (onychomycosis)
  • Saourad agar at room tem 1-3 weeks
  • DERMATOPHYTE TEST MEDIUM (DTM) allows for early detection->3days based on phenol red color change (pH)
  • certain species of Microsporum-infected hair exhibit fluorescence
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13
Q

What is the infective state of dermatophyte dz and how is it visualized

A

ARTHROCONIDIUM is the infective stage of dz, it can be visualized microscopically in 10% KOH wet mount

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14
Q

Trichophytin

A

Galactomannan peptide
Crude antigen of dermatophytes
a. CHO component: immediate response
b. peptide component: delayed response

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15
Q

10% Potassium Hydroxide: what does it do?

A

digests human tissue, leaves fungal components intact

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16
Q

Dermatophyte test medium

A

selective (cyclohexamide & antibiotics) & differential (color change based on fermentation of sugars)

  • dermatophytes utilize nitrogenous components of carbohydrates
  • change pH-color changes to red
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17
Q

Fluorescence can be used to visualize what?

A

Microsporum dermatophytes

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18
Q

3 classifications of dermatophytes

A
  1. Zoophilic: animal pathogens that may be transmitted to ppl
  2. Antrophophilic: human transmission
  3. Geophilic: transmitted through soil to ppl
    - usually invade non-viable keratinized tissue
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19
Q

Habitat and Distribution of dermatophytes

A

(U) on MOIST AREAS of BODY

worldwide distribution, but most prevalent in the TROPICS

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20
Q

Arthrospores: where may they be found

A

fragmental hyphal elements in hair, nails, outer skin

also see infections by MICROCONIDIA< MACROCONIDIA & SEXUAL SPORES

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21
Q

Dermatophyte infections: sxs in ppl

A
  • lesions are inflamed at edges w/a central clearing zone

- HAIR LOSS W/ITCHING, BUT NOT DEBILITATING

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22
Q

Predisposing factors & risk factors for dermatophyte infections

A

predisposing factors: nail trauma, HIV, CM, immunosuppressive meds
risk factors: communal bathing facilities, immunocomprimised status, Cushing syndrome (inc. cortisol interferes w/inflammation) & some contact sports (eg. Wrestling)
-DISSEMINATED DZ POSSIBLE in HIV pts (T. mentagrophytes & M. canis)

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23
Q

Arthrospores

A

(arthroconidia) -an asexual spore
- disseminate from one host to another (P-to-P transmission)
- survive in environment
- infectious

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24
Q

Microconidia

A

asexual spore (see pic on slide 11)

25
Q

Macroconidia

A

segmented, “where cell has all reproductive fxns????” ????slide 11?????

26
Q

Dermatophytid: what is this? most common when?

A
  • “Id reaction”: allergic dermal rxn to fungal antigens occurring in areas devoid of organisms
  • most (C) in Tinea pedis (athlete’s foot)
  • sometimes a result of excessive tx or pruritis
  • tx as allergy: corticosteroids, wet compresses, antihistamines
27
Q

Dermatophytes-Tx & control

A
  1. Antifungal agents: AZOLE CREAMS: micoazole, clotrimazole, etc; SYSTEMIC ANTIFUNGALS: terbinafine, itraconazole
  2. Laser & removal of infected tissue (eg. Nail)
  3. Control: good personal hygiene, keep skin as dry as possible, spores are shed on skin and hair so good housecleaning w/common DISINFECTANTS, CHLORINE BLEACH & DETERGENTS
28
Q

Tinea capitas common causative agents (3)

A

M. canis
T. mentagrophytes
T. tonsurans (most (C) in US)

29
Q

Tinea capitas: affects which pop, involves what, looks like….

A
  • mostly a childhood dz
  • involves ENDOTHRIX (Trichophyton) & ECTOTHRIX OF HAIR along w the SCALP
  • some spp. produce a black dot ringwork
  • infected hair can break off->alopecia
  • intense inflammation, scarring & permanent alopecia can occur
30
Q

Tinea capitis aka

A

ringworm of the scalm

31
Q

Tinea capitis tx

A

Griseofulcin is effective

32
Q

Tinea capitis infection origin

A

can be zoonotic (puppies & kittens)

33
Q

Tinea pedis agents (3)

A

E. floccosum
T. mentagrophytes
T. rubrum

34
Q

Tinea pedis sxs

A

itching, peeling & cracking of the skin are the principle manifestation
(U) toe webs & soles
MOST PREVALENT OF ALL DERMATOPHYTOSES

35
Q

Tinea corporis & Tinea cruris agents (4)

A

M. canis
E. floccosum
T. mentgrophytes
T. rubrum

36
Q

Tinea corporis aka

A

jock itch

37
Q

Tinea cruris aka

A

ringworm of the groin

38
Q

Tinea corporis & tinea crurus predisposing factors

A

diabetes, obesity, excessive perspiration

39
Q

Tinea corporis & tinea cruris transmission

A

direct & indirect contact objects

towels, clothing, bed linens

40
Q

Tinea unguium: aka & 3 spp.

A 
onychomycosis (ringwork of the nail)
E. floccosum
T. mentagrophytes
T. rubrum
*prevalent fungal infection in adults
41
Q

Tinea unguium clinical manifestation

A
  • finger & toenails become discolored & thick
  • may be mistaken for psoriasis
  • (U) has fungal involvement (Candida)
42
Q

Tinea unguium tx

A

systemic antifungals work better than topical agents

43
Q

Tinea versicolor aka

A

Malassezia furfur

44
Q

Malassezia furfur morphology & physiology

A

another cutaneous fungi

microscopically: SPAGHETTI & MEATBALLS (short, unbranched hyphae & somewhat spherical cells)
- lipophilic growth factor
- yeast like colonies

45
Q

Malassezia furfur epidemiology

A

worldwide, more (C) in TROPICS

(U) in YOUNG ADULTS

46
Q

Malassezia furfur clinical presentation

A

lesion occurs as a macular patch of DEPIGMENTED or HYPERPIGMENTED SKIN that may enlarge

47
Q

Malassezia furfur identification

A

microscopic exam in skin scrapings (in KOH)

48
Q

Malassezia furfur therapy

A

topical selenium sulfide, miconazole

49
Q

Tinea nigra aka

A

Hortaea werneckii

50
Q

Hortaea werneckii morph & phys

A 
diporphic species (yeast & mold)
-CAN GROW IN SATURATED SALT SOLUTIONS
51
Q

Hortaea werneckii epidemiology

A

tropical dz

52
Q

Hortaea werneckii presentation

A

brownish lesion

53
Q

Hortaea werneckii identification

A

KOH & microscopy

54
Q

Hortaea werneckii therapy

A

Tincture of iodine or azole creams

55
Q

Sarcoptes scabiei: the basics (no morphology)

A

burrowing mite, THE MOST SERIOUS MITE
-close relative of ticks
leased to scabies, crusted scabies, mange, seven-year-itch, etc

56
Q

Sarcoptes scabei morphology/biology

A

small mite with short legs
FEMALE: fertilized on the skin surface, burrows to the epidermis, COMPLETES LIFE CYCLE IN 5 WEEKS, dies in the burrow
MALE: shorter life span, remains on the skin surface or produces a shallow burrow; eggs laid under skin, larva emerges from the egg after 4 days, adult mite develops 2 weeks after hatching

57
Q

Sarcoptes scabiei pathogenicity

A

burrowing causes majority of clinical issues

INTENSE PRUIRITIC ERUPTION (WORSE AT NIGHT)

58
Q

Crusted (Norwegian) Scabes clinical manifestion

A

incubation period=~1 month
crusted scaling lesions that are intensely pruritic
observed readily

Microbiology test 3 (8 decks)

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