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

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

Flashcards in Exam #8: Superficial, Cutaneous, & Subcutaneous Fungal Infections Deck (58):

What are superficial mycoses?

Infections limited to the outermost layers of the skin (stratum corneum) and hair (cuticle)
- No inflammatory reaction
- No physical discomfort
- Easily recognized and treated


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

- Common superficial infection of the skin caused by Malassezia furfur
- "Tinea Versicolor"


List the characteristics of Malassezia furfur.

Part of the normal flora


When is clinical disease seen with Malassezia furfur?

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


What is the clinical presentation of Pityriasis Versicolor?

- 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


How is Pityriasis Versicolor diagnosed?

- Direct observation of skin scrapings, typically following KOH prep
- Pattern is referred to as "spaghetti (hyphae) & meatballs (mold)"


What is the treatment for Pityriasis Versicolor?

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


What is tinea nigra?

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.


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

Exophiala werneckii
- Dimorphic fungus
- Most common in tropics
- Organism produces melanin-->brown or black color


How is Exophiala werneckii transmitted?

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


How does Tinea nigra present?

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

*Note that the organism produces melanin


How is Tinea nigra diagnosed?

- Microscopic examination of skin scrapings
- Two-celled yeast forms with thick walled septate hyphae that contain dark pigmentation


How is Tinea nigra treated?

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

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


What is Black Piedra?

- "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


What is White Piedra?

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


What is the clinical syndrome seen with Black Piedra?

- Minute hard nodules are firmly attached to the hair of the scalp
- Dark appearance & makes metallic sound when combing hair


What is the clinical syndrome seen with White Piedra?

- Soft white nodules that usually affects pubic hair, axillary hair, beards, mustaches, eyebrows, & eyelashes


How are the Piedras diagnosed?

Microscopic examination of infected hairs

*Note that the DD contains nits of head lice


How are the Piedras treated?

- Shaving or closely cropping hair
- Improving hygiene
- Topical antifungals


What are dermatophytes?

- Fungi that infect the skin, nails, and hair
- Specifically these fungi are limited to the keratinized layers, epidermis, and dermis


What are the three genera that are dermatophytes?

1) Microsporum
2) Trichophyton
3) Epidermophyton


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

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


What are the predisposing factors to the dermatophytes?

Closed shoes
Community showers


Describe the clinical syndrome caused by the dermatophytes.

- Evoke inflammatory reaction
- Itching and scaling of the skin


How is the clinical manifestation of the dermatophytes described?

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


Describe the presentation of Tinea pedis.

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


What is Tinea corporis?

Ring Worm


Describe the classic presnetation of Ring Worm?

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


What is Tinea capitis?

Scalp infection


What is a Favus?

Mass of hyphal elements surrounding the base of the hair shaft


What is Tiena curis?

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


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

- Infection of nail plate and nail bed
- "onychomycosis"


Why diagnose the dermatophytic infection?

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


How are dermatophytic infections diagnosed?

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


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

- 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


How are dermatophyte infections treated?

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


What is cutaneous candidiasis?

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


What is the most common cause of diaper rash?

C. albicans


What is the most common cause of "dishwater hands"

C. albicans


What is chronic mucocutaneous Candidiasis?

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

*Treated with Oral azoles


What patient populations are at risk for disseminated Candidiasis?

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

*treated with IV amphotericin B


What are subcutaneous mycoses?

- Fungal infections of the dermis, subcutaneous tissue, and bone


How are the subcutaneous mycoses acquired?

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


What is sporotrichosis?

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


What causes sporotrichosis?

- 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


Describe the clinical syndrome of Sporotrichosis.

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


How is Sporotrichosis diagnosed?

Cultivation of the organism from tissue samples or pus


What is the treatment for Sporotrichosis?

- Oral potassium iodine
- Oral azole


What is Chromoblastomycosis?

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


Describe the presentation of Chromobastomycosis.

Red/gray cauliflower like lesions



How is Chromoblastomycosis diagnosed?

- Brown-pigmented hyphae in skin scrapings
- Medlar bodies


What are Medlar bodies?

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


How is Chromoblastomycosis treated?

- Surgical removal
- 5-flurocytosine


What is Mycetoma?

Madura foot
- Chronic subcutaneous infection typically affecting the foot


How is mycetoma transmitted?

Traumatic inoculation of soil-inhabiting fungi


Describe the clinical syndrome seen in Mycetoma.

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


How is Mycetoma diagnosed?

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


How is Mycetoma treated?

Surgery & antifungal drugs

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