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Microbiology > Exam #8: Superficial, Cutaneous, & Subcutaneous Fungal Infections > Flashcards

Exam #8: Superficial, Cutaneous, & Subcutaneous Fungal Infections Flashcards

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1
Q

What are superficial mycoses?

A

Infections limited to the outermost layers of the skin (stratum corneum) and hair (cuticle)

  • No inflammatory reaction
  • No physical discomfort
  • Easily recognized and treated
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2
Q

What is Pityriasis Versicolor? What is an alternative name for Pityruasus Versicolor?

A
  • Common superficial infection of the skin caused by Malassezia furfur
  • “Tinea Versicolor”
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3
Q

List the characteristics of Malassezia furfur.

A

Dimorphic
Part of the normal flora
Lipophillic

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4
Q

When is clinical disease seen with Malassezia furfur?

A

When environmental factors promote growth in the hyphal phase i.e. a transition from the yeast form to the mold form

  • Increased lipid production
  • Moist heat
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5
Q

What is the clinical presentation of Pityriasis Versicolor?

A
  • Numerous irregularly shaped scaly patches that are yellow-brown to dark brown in color
  • Hyper or hypo-pigmentation
  • Patients generally seek medical care for cosmetic reasons
  • Skin changes are more prominent in the summer months b/c affected regions do NOT tan well
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6
Q

How is Pityriasis Versicolor diagnosed?

A
  • Direct observation of skin scrapings, typically following KOH prep
  • Pattern is referred to as “spaghetti (hyphae) & meatballs (mold)”
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7
Q

What is the treatment for Pityriasis Versicolor?

A
  • Topical treatment with keratolytic agents (salicylic acid)
  • Topical azoles are also effective
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8
Q

What is tinea nigra?

A

Superficial fungal infection that is caused by traumatic inoculation with fungus from soil, sewage, wood, or compost; thus, it most often affects the palms of the hands and soles of the feet.

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9
Q

What organism causes tinea nigra? List the characteristics of the causative organsim.

A

Exophiala werneckii

  • Dimorphic fungus
  • Most common in tropics
  • Organism produces melanin–>brown or black color
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10
Q

How is Exophiala werneckii transmitted?

A

Traumatic inoculation with fungus from soil, sewage, wood, or compost

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11
Q

How does Tinea nigra present?

A
  • Distinct oval-shaped lesions on hands and feet
  • Light brown to black color

*Note that the organism produces melanin

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12
Q

How is Tinea nigra diagnosed?

A
  • Microscopic examination of skin scrapings

- Two-celled yeast forms with thick walled septate hyphae that contain dark pigmentation

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13
Q

How is Tinea nigra treated?

A
  • Topical treatment with keratolytic agents (salicylic acid)
  • Topical azoles are also effective

*Thus, treatment is similar to Pityriasis Versicolor (M. furfur)

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14
Q

What is Black Piedra?

A
  • “Piedra” is spanish for “stone”
  • These are fungal infections of the hair shaft characterized by hard or gritty granules along the hair shaft
  • Black Piedra is seen in tropical climates (vs. White Piedra)
  • Caused by Piedra hortae
  • Dark ascospores
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15
Q

What is White Piedra?

A
  • Peidra infection that is seen in temperate & semi-tropical climates including the southern US.
  • Caused by Trichonsporon beigelii
  • Mycelium
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16
Q

What is the clinical syndrome seen with Black Piedra?

A
  • Minute hard nodules are firmly attached to the hair of the scalp
  • Dark appearance & makes metallic sound when combing hair
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17
Q

What is the clinical syndrome seen with White Piedra?

A
  • Soft white nodules that usually affects pubic hair, axillary hair, beards, mustaches, eyebrows, & eyelashes
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18
Q

How are the Piedras diagnosed?

A

Microscopic examination of infected hairs

*Note that the DD contains nits of head lice

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19
Q

How are the Piedras treated?

A
  • Shaving or closely cropping hair
  • Improving hygiene
  • Topical antifungals
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20
Q

What are dermatophytes?

A
  • Fungi that infect the skin, nails, and hair

- Specifically these fungi are limited to the keratinized layers, epidermis, and dermis

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21
Q

What are the three genera that are dermatophytes?

A

1) Microsporum
2) Trichophyton
3) Epidermophyton

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22
Q

What is the difference between geophilic, zoophilic, and anthropophilic?

A 
Geophilic= isolated from soil 
Zoophilic= animal contact 
Anthropophilic= person-to-person
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23
Q

What are the predisposing factors to the dermatophytes?

A

Closed shoes

Community showers

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24
Q

Describe the clinical syndrome caused by the dermatophytes.

A
  • Evoke inflammatory reaction

- Itching and scaling of the skin

25
Q

How is the clinical manifestation of the dermatophytes described?

A

Tinea, followed by the location:

Tinea pedis= athlete's foot 
Tinea barbae= beard 
Tinea corporis= Torso
Tinea manus= hands
Tinea unguium= nails 
Tinea cruris= groin

*Note that these are simply clinical descriptions; these are NOT the names of the infecting organisms

26
Q

Describe the presentation of Tinea pedis.

A

Tinea pedis is colloquially known as “athlete’s foot”

- Chronic infection of the toe webs that may also involve the heel & side of the foot

27
Q

What is Tinea corporis?

A

Ring Worm

28
Q

Describe the classic presnetation of Ring Worm?

A

Erythematous, round, scaly patch with a raised advancing border that most often occurs on the trunk

29
Q

What is Tinea capitis?

A

Scalp infection

30
Q

What is a Favus?

A

Mass of hyphal elements surrounding the base of the hair shaft

31
Q

What is Tiena curis?

A

Jock itch i.e. dry erythematous lesion in the groin

32
Q

What is Tinea unguinum? What is another name for Tinea unguinum?

A
  • Infection of nail plate and nail bed

- “onychomycosis”

33
Q

Why diagnose the dermatophytic infection?

A

1) Determine source
2 Confirm differential
3) Anticipate response to therapy

34
Q

How are dermatophytic infections diagnosed?

A

Direct observation of fungal elements in skin, scrapings, or samples of hair or nails

35
Q

What is a wood’s lamp? What is a wood’s lamp used for?

A
  • A wood’s lamp is a specialized lamp that emits UV light
  • Used to examine lesions on scalp or bread
  • Microsporum exhibit a green fluorescence under a wood’s lamp
36
Q

How are dermatophyte infections treated?

A

1) Exfoliation or removal of infection skin
2) Application of topical antifungal (azole)

*Note that Tinea unguinum is more difficult to treat b/c of the nail and requires prolonged oral antifungals

37
Q

What is cutaneous candidiasis?

A

Skin in nail infections caused by C. albicans

*Note that these infections most commonly occur in areas that are most or frequently become wet

Treated with topical azole

38
Q

What is the most common cause of diaper rash?

A

C. albicans

39
Q

What is the most common cause of “dishwater hands”

A

C. albicans

40
Q

What is chronic mucocutaneous Candidiasis?

A
  • Superficial candida infections at several anatomical sites
  • Most commonly seen in T-cell deficits & endocrine disorders

*Treated with Oral azoles

41
Q

What patient populations are at risk for disseminated Candidiasis?

A

1) Newborns
2) Surgery & burn patients
3) Transplant recipients
4) Patients receiving chemotherapy

*treated with IV amphotericin B

42
Q

What are subcutaneous mycoses?

A
  • Fungal infections of the dermis, subcutaneous tissue, and bone
43
Q

How are the subcutaneous mycoses acquired?

A
  • Trauma

- Etiological agents are typically found in the soil or on vegitation

44
Q

What is sporotrichosis?

A

-A chronic fungal infection of the cutaneous & subcutaneous tissue, and lymphatic system

45
Q

What causes sporotrichosis?

A
  • Sporothrix schenckii, which is commonly found in the soil, on plants, and in decaying vegetation
  • Gardeners, farmers, and landscapers are at increased risk of infection
  • Inoculation occurs via rose thorns, wood splinters, grasses, and moss
46
Q

Describe the clinical syndrome of Sporotrichosis.

A
  • Painless granulomatous lesion at the site of infection
  • Lesion ulcerates creating an open sore
  • Secondary lesions may develop along the draining lymphatic tract
47
Q

How is Sporotrichosis diagnosed?

A

Cultivation of the organism from tissue samples or pus

48
Q

What is the treatment for Sporotrichosis?

A
  • Oral potassium iodine

- Oral azole

49
Q

What is Chromoblastomycosis?

A

A disease of the tropics caused by a variety of fungi that inhabit the soil & have brown or black pigment in their cell walls

50
Q

Describe the presentation of Chromobastomycosis.

A

Red/gray cauliflower like lesions

*Painless

51
Q

How is Chromoblastomycosis diagnosed?

A
  • Brown-pigmented hyphae in skin scrapings

- Medlar bodies

52
Q

What are Medlar bodies?

A

“Copper pennies” or copper-colored spherical cells that are seen on microscopic examination of infected tissue

53
Q

How is Chromoblastomycosis treated?

A
  • Surgical removal

- 5-flurocytosine

54
Q

What is Mycetoma?

A

Madura foot

- Chronic subcutaneous infection typically affecting the foot

55
Q

How is mycetoma transmitted?

A

Traumatic inoculation of soil-inhabiting fungi

56
Q

Describe the clinical syndrome seen in Mycetoma.

A
  • Lesions on the foot that begin as slow growing papules, which ulcerate, releasing pus and blood
  • Underlying bone becomes involved producing pitted lesions
57
Q

How is Mycetoma diagnosed?

A

Direct observation of colored grains in pus, tissue, or discharge

58
Q

How is Mycetoma treated?

A

Surgery & antifungal drugs

Microbiology (49 decks)

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