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Fungi Classification (Superficial+Cutaneous) Flashcards

1
Q

Is fungi successful at invading often

A

Humans have a high level of innate immunity to fungi and most of the infections they cause are mild and self-limiting

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2
Q

Body’s protection mechanisms against fungi

A 
Fatty acid content of the skin pH of the skin, 
Mucosal surfaces and body fluids 
Epithelial turnover 
Normal flora 
Cilia of respiratory tract
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3
Q

Superificial mycoses (infection)

A

Infections limited to the outermost layers of the skin and hair
Tinea versicolor, Tinea nigra, Black piedra, White piedra

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4
Q

Tinea versicolor (Etiological agent+Symptoms)

A

Malassezia furfur

Hypopigmented macules

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5
Q

Tinea versicolor (Lab ID)

A

“spaghetti and meatballs” appearance of organism in skin scrapings (KOH wet mount) -> round yeast cells surrounded by angular mycelia
Wood light examination - golden-white fluorescence
PAS
SDA - yeast colonies

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6
Q

Tinea versicolour (Risk factors + Treatment)

A 
Blood group O, Addison's disease, steroid therapy, IV (parenteral) therapy -systemic
Grows where skin+oil accumulates
Treatment: 
Selenium Sulfide Shampoos
Ketoconazole 2% shampoo /oral
Imidazoles 
Terbinafine, Itraconazole, Fluconazole
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7
Q

Tinea nigra (Transmission + Etiological agent)

A

Etiological agent
Exophiala werneckii
Infection via inoculation

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8
Q

Tinea nigra (Symptoms+lab ID)

A 
Smooth, flat lesions affecting palms
Lab ID
Microscopically after treatment with 10% KOH
-branching septate hyphae 
SDA 
Black, moist and shiny mycelium; grows until 15 days 
-Budding; blastospores seen 
prominent darkly-pigmented septa
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9
Q

Piedra

A

fungal infection of the hair
-presence of stony hard nodules along the hair shaft
piedraia hortae (Black piedra) Trichosporon beigelii (white piedra)
-scalp, beard and mustache

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10
Q

Piedra Pathogenesis

A

Black piedra
-affects only the hairs of the scalp where it invades beneath the cuticle, then expands and ruptures to spread around the hair shaft, forming dark brown and black nodules
Trichosporon beigelii (White peidra)
-light brown soft nodules on the beard or mustache
-less firmly attached than those of black piedra

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11
Q

Piedra (Lab ID)

A

P hortae
-Grows after 20 days
-Dark thick walled hyphae
T beigelli
-SDA; rapid growth
- Creamy, slimy growth -> wrinkled+darker
-Hyaline hyphae, blastoconidia, and arthospores are seen on Tween 80

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12
Q

Cutaneous mycoses

A

Refers to certain fungal infection of the skin caused by dermatophytes
-Hair, skin, nails
-Trichophyton, Microsporum, Epidermophyton
-> Keratin metabolizing filamentous fungi
Microsporum - infections on skin and hair (not nail)
Epidermophyton - infections on skin and nails (not hair)
Trichophyton - infections on skin, hair, and nails. .

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13
Q

Dermatophyte infection

A
  • lesion with outer ring of an active infection with central healing in the ring.
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14
Q

Dermatophyte infection - severity

A

(1) strains/spp of fungus involved
(2) sensitivity of the host to pathogenic fungus.
More severe reactions occur when a dermatophyte crosses non-host lines (e.g., from an animal species to man).

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15
Q

Dermatophyte saprophytic to a parasitic lifestyle

A

Geophilic species - keratin-utilizing soil saprophytes (e.g., M. gypseum, T. ajelloi)
Zoophilic species - keratin-utilizing on hosts - living animals (e.g., M. canis, T. verrucosum)
Anthropophilic species - keratin-utilizing on hosts - humans (e.g., M. audounii, T. tonsurans)

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16
Q

Cutaneous mycosis classification

A 
Based on area of infection
Tinea capitis
Tinea pedis
Tinea corporis
Tinea cruris
Tinea barbae
Tinea unguium 
Tinea favosa
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17
Q

Tinea capitis (Spp+ID)

A
  • Scalp+hair
  • Trichophyton and Microsporum
  • Microsporum canis and Microsporum audouinii (children) -> Grey patch ringworm -> hair glows under lamp
  • Trichophyton tonsurans and Trichophyton mentagrophytes - black dot ringworm
  • > infected hair does not glow
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18
Q

Tinea capitis (Transmission+Pathogenesis)

A
  • Can spread from animals/people
  • scaly, erythematous lesions, topical and sometimes deep, ulcerative, kerion like eruptions
  • Lesions cause thinning hair which falls leaving dark stumps (Black dot)
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19
Q

Tinea capitis (Treatment)

A

-Must treat hair follicle -> topical ineffective
Griseofulvin (children)
Imidazoles, terbinafine.
Steroids for inflamed lesions like Kerion

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20
Q

Tinea pedis

A
  • feet, mostly toe webs and soles
  • Ttrichophyton mentagrophytes, Trichophyton rubrum and Epidemophyton floccosum
  • floors of pools, tight shoes, men affected more
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21
Q

Tinea pedis - Clinical varieties

A

Intertriginous type
- slow developing fissuring between the 4th and 5th toe and spreading to others.
Hyperhydrosis and itching is common.
Squamous or hyperkeratotic type
- the soles, sides of the feet and heels - well-defined, red or purplish scaly patches
-secondary bacterial infection common.
Acute vesiculo-pustullar-bullous type - groups of deep pruritic vesicles,vesiculopustules and bullae.
-in step, midsole and heel

22
Q

Tinea pedis - Treatment

A

Alternate shoes, Absorbent powders, Change socks
Topicals and/or Systemics.
Topical: naftfine more effective than azoles.
Steroids if inflamed.
Systemic allylamines or azoles
Treat secondary bacterial infections.
Steroids for severe inflammation and ID.

23
Q

Tinea corporis

A

-Ringworm of body - simple scaling to deep granuloma
-Persons/soil
-Males affected more
Trichophyton rubrum ,
Trichophyton tonsurans,
Trichophyton mentagrophytes,
Microsporum canis,
Microsporum. audouinii and
Microsporum gypseum.

24
Q

Tinea corporis - Clinical manifestations

A

Anular type - lesion center is inactive, pink scaly, margin is active, raised and reddish

Hypertiform variety - small vesicular lesions studded together with many micropapules and vesicles.

Plaque form scaly red - plaques with pronounced vesiculation and crusting

Kerion type - also called Tinea profunda; deep granulomatous lesions

25
Tinea corporis (Treatment)
All forms of tinea corporis caused by T. rubrum, T. mentagrophytes, T. tonsurans, M. canis, and M. audouinii are treatable with topical agent containing ketoconazole, miconazole
26
Tinea cruris
- groin, perineum and perianal region - Epidermophyton floccosum and Trichophyton spp - Transmission: public toilet seats, sex, laundry, feet fungus - elevated, bilateral lesions
27
Tinea cruris (Treatment)
Ketaconazole, miconazole
28
Tinea barbae
- Trichophyton and Microsporum - bearded area of the face and neck - Superficial lesions - cattle to man
29
Tinea barbae (Features)
- Brittle/lusterless hair | - Deep type of infection - deep follicular pustules, which result in abscess formation
30
Tinea unguium
- nails - Trichophyton rubrum, Trichophyton mentagrophytes and Epidermophyton floccosum - Transmission - soil
31
Tinea unguium (clinical feature)
- begin distally/at the lateral edge of the nail - nail yellow/white/brown and pitted - Toenail affect more - Onchomycosis - infections of nail not caused by Dermatophytes e.g. Candiasis
32
Tinea unguium (treatment)
``` Debridement of infected area helps penetration / comfort. Mechanical Urea products (ex carmol) ``` Topical Treatment: Can be effective for limited involvement and for prevention. Agents Mycocide Nail solution Oral therapy Effective. Relapse rate 15-20 % in one year. Itraconazole 200 mg /day. 6 weeks/12 weeks
33
Tinea favosa
- chronic fungal infection caused by Trichophyton schoenleinii, Trichophyton violaceum or Microsporum gypseum - scalp - yellowish, cup-shaped crusts with “mousy” odor. - starts off small and develops into cup shape - Can lead to balding if untreated
34
Tinea favosa vs Tinea unguium
Tinea favosa of the nail is undistinguishable from other forms of tinea unguium.
35
General Lab ID
Spaghetti meatball appearance is classical for yeast The most common pathogen for tinea capitus used to be microsporoum. It is now T. Tonsauran thus render wood’s light useless
36
Trichophyton schoenleinii
Trichophyton schoenleinii Endothrix infection of hair - large inverted cones of hyphae and arthroconidia at the base of the hair follicle -branching hyphae throughout the length of the hair shaft. No conidia (micro- or macro-)
37
Trichophyton violaceum
Trichophyton violaceum Attacks hair, scalp, skin and nails. Nail infections are persistent. Endothrix (hair shaft infection) -Rarely produces microconidia and macroconidia. -Hyphae coarser in appearance than seen in other dermatophytes. Chlamydoconidia are seen in culture
38
Microsporum audouinii
Microsporum audouinii Usually devoid of conidia (macro- or microconidia). Bizarre - shaped macrocondia: -thick walled club or spindle shaped, -multiseptate, with rough surface microconidia -rare, terminal chlamydospores. Septate hyphae with terminal chlamydoconidia, often pointed at the end
39
Specimen
Dermatophytes Specimen: skin scrapings, nails, hair Diagnostic characteristics: Septate hyphae/spherical yeast cells depending on etiological agent Blastomyces dermatitidis Specimen: Pus, sputum, skin sample Diagnostic characteristics: Large Yeast cells -dimorphic fungus with yeast cells in tissue.
40
Diagnosis of Dermatophytosis
Basic diagnostic techniques KOH (skin-look for hyphae, culture nails, look for spores in hair w + w/o KOH) -Growth inside hair shaft (endothrix) -Growth inside and outside hair shaft (ectothrix) Culture Woods light(T.capitis)
41
Microsporum audouinii (Dermatophytes ID)
``` Usually devoid of conidia (macro/microconidia). Bizarre - shaped macrocondia: club or spindle shaped, multiseptate, with rough surface ---microconidia rare, terminal chlamydospores. ```
42
Microsporum canis
Thick walled, spindle shaped, large, multiseptate rough walled macrocondia with curved tip and knobby projections --- sparse microconidia: clavate (club-shaped), smooth walled, and literally attached hyphae
43
Microsporum gypsum
Numerous, thick –walled, cigar -shaped multiseptate macroconidia with spiny surface and rounded tips ---- sparse, clavate, smooth –walled micorconidia
44
Trichophyton
arthrospores in parallel rows inside the hair (endothrix type) or in parallel rows outside the hair (ectothrix type) and in chains of small arthrospores or chains of large arthrospores
45
Trichophyton mentagrophytes
Microspores: arranged in small grape like clusters, - -coiled, spiral hyphae may be observed - --macrocondia: rare, thin walled, smooth and cigar shaped.
46
Trichophyton tonsurans
Microconidia: Abundant tear, club -, or balloon-shaped Macrocondia: rare smooth walled, cylindrical.
47
Trichophyton rubrum
microconidia: Tear shaped bore laterally form long strands of hyphae Macrocondition: rare, thin-walled, smooth, pencil –shaped.
48
Trichophyton verrucosum
Large-spored ectothrix. chains of chlamydoconidia and antler-like hyphae. small microconidia and occasionally macroconidia are produced.
49
Trichophyton schoenleinii
Endothrix infection of hair -large inverted cones of hyphae and arthroconidia at the base of the hair follicle and branching hyphae throughout the length of the hair shaft. No conidia (micro- or macro-)
50
Trichophyton violaceum
Endothrix Rarely produces microconidia and macroconidia. Hyphae coarser in appearance than seen in other dermatophytes. Chlamydoconidia in culture
51
Epidemophyton floccosum
Many club-shaped, smooth walled macroconidia with two to four cells in clusters microcondia absent
52
Fungal Cultures
DTM (Dermatophyte Test Medium) Yellow to red is (+). Sabouraud’s Media Molds

Mycology (6 decks)

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