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

Dermatomycoses & Ectoparasitic Infections (session 23) 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
Macroconidia
segmented, "where cell has all reproductive fxns????" ????slide 11?????
26
Dermatophytid: what is this? most common when?
- "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
Dermatophytes-Tx & control
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
Tinea capitas common causative agents (3)
M. canis T. mentagrophytes T. tonsurans (most (C) in US)
29
Tinea capitas: affects which pop, involves what, looks like....
- 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
Tinea capitis aka
ringworm of the scalm
31
Tinea capitis tx
Griseofulcin is effective
32
Tinea capitis infection origin
can be zoonotic (puppies & kittens)
33
Tinea pedis agents (3)
E. floccosum T. mentagrophytes T. rubrum
34
Tinea pedis sxs
itching, peeling & cracking of the skin are the principle manifestation (U) toe webs & soles MOST PREVALENT OF ALL DERMATOPHYTOSES
35
Tinea corporis & Tinea cruris agents (4)
M. canis E. floccosum T. mentgrophytes T. rubrum
36
Tinea corporis aka
jock itch
37
Tinea cruris aka
ringworm of the groin
38
Tinea corporis & tinea crurus predisposing factors
diabetes, obesity, excessive perspiration
39
Tinea corporis & tinea cruris transmission
direct & indirect contact objects | towels, clothing, bed linens
40
Tinea unguium: aka & 3 spp.
``` onychomycosis (ringwork of the nail) E. floccosum T. mentagrophytes T. rubrum *prevalent fungal infection in adults ```
41
Tinea unguium clinical manifestation
- finger & toenails become discolored & thick - may be mistaken for psoriasis - (U) has fungal involvement (Candida)
42
Tinea unguium tx
systemic antifungals work better than topical agents
43
Tinea versicolor aka
Malassezia furfur
44
Malassezia furfur morphology & physiology
another cutaneous fungi microscopically: SPAGHETTI & MEATBALLS (short, unbranched hyphae & somewhat spherical cells) - lipophilic growth factor - yeast like colonies
45
Malassezia furfur epidemiology
worldwide, more (C) in TROPICS | (U) in YOUNG ADULTS
46
Malassezia furfur clinical presentation
lesion occurs as a macular patch of DEPIGMENTED or HYPERPIGMENTED SKIN that may enlarge
47
Malassezia furfur identification
microscopic exam in skin scrapings (in KOH)
48
Malassezia furfur therapy
topical selenium sulfide, miconazole
49
Tinea nigra aka
Hortaea werneckii
50
Hortaea werneckii morph & phys
``` diporphic species (yeast & mold) -CAN GROW IN SATURATED SALT SOLUTIONS ```
51
Hortaea werneckii epidemiology
tropical dz
52
Hortaea werneckii presentation
brownish lesion
53
Hortaea werneckii identification
KOH & microscopy
54
Hortaea werneckii therapy
Tincture of iodine or azole creams
55
Sarcoptes scabiei: the basics (no morphology)
burrowing mite, THE MOST SERIOUS MITE -close relative of ticks leased to scabies, crusted scabies, mange, seven-year-itch, etc
56
Sarcoptes scabei morphology/biology
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
Sarcoptes scabiei pathogenicity
burrowing causes majority of clinical issues | INTENSE PRUIRITIC ERUPTION (WORSE AT NIGHT)
58
Crusted (Norwegian) Scabes clinical manifestion
incubation period=~1 month crusted scaling lesions that are intensely pruritic observed readily

Microbiology test 3 (8 decks)

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