question

Name 4 groups of parasites that can infect the superficial structures of the hair, nails, and stratum corneum of the skin.

answer

Pityriasis versicolor, Tinea nigra, black piedra, white piedra

question

What disease is caused by Malassezia furfur?

answer

Pityriasis (tinea) versicolor

question

What kind of disease is pityriasis (tinea) versicolor?

answer

Chronic, superficial fungal disease of the skin.

question

Describe pityriasis (tinea) versicolor.

answer

The lesions are hypopigmented or hyperpigmented macules. The most common sites include the back, axillary, upper arm, chest, and neck. The lesions scale easily, giving them a chalky appearance. There is no surrounding erythema, the lesions are not elevated, causing only mild itching. Otherwise, no discomfort. Does not elicit an immune response.

question

What is the normal habitation of the organism that causes tinea versicolor?

answer

Around the openings of hair follicles. Not found in animals. Most commonly found in adolescents and young adults.

question

How is tinea versicolor transmitted? Who is normally affected?

answer

Person-to-person spread, direct or indirect. Young adults and adolescents are most often affected; up to 60% of populations in tropical regions.

question

How is tinea versicolor diagnosed?

answer

Direct microscopy: epidermal scales with 10% KOH. "Spaghetti and meatballs" appearance. Large round yeasts with angular hyphae. Wood lamp: fluoresce yellow-green. Not necessary to culture.

question

How is tinea versicolor treated?

answer

Azoles. Smaller infected areas can be treated with selenium sulfide in a shampoo.

question

Where is tinea nigra most frequently found on the body?

answer

Palms of the hands.

question

What type of infection is tinea nigra?

answer

Superficial infection located on the palms.

question

Name and describe the disease that Hortaea werneckii causes?

answer

Tinea nigra; the lesions are dark-colored, non-scaling, and asymptomatic (no inflammatory reaction). The yeast is a black yeast that produces melanin (dermatiaceous).

question

Tinea nigra is normally found in what regions?

answer

Tropical or semitropical areas of Central and South America, Africa, Asia.

question

How is tinea nigra diagnosed?

answer

Skin scrapings prepared with 10% KOH. Can culture on Sabouraud's media; appears as pale, moist yeast colonies which darkens with age (due to the growth of hyphae).

question

How is tinea nigra treated?

answer

Topical antifungals such as azoles and Whitefield's ointment.

question

Describe black piedra.

answer

Asymptomatic fungal infection of the hair shaft. The nodules are dark in color, hard, and firmly attached to the hair shaft. Usually affects scalp hair; eventually the fungus may weaken the hair shaft to the extent that it breaks.

question

Black piedra is normally found in what regions?

answer

Tropical regions such as Central and South America and Africa.

question

How is black piedra diagnosed?

answer

Dermatiaceous hyphae and ascospores. Culture on Sabouraud's medium and incubate at room temp (25 degrees) for 4-6 weeks.

question

How is black piedra treated?

answer

Haircut and regular washings.

question

What is white piedra?

answer

Asymptomatic fungal infection of the hair shafts. Light-colored, soft nodules that are loosely attached to hairs and my cause the hair shafts to break. Mostly found on the hair on the groin and axillae.

question

The genus Trichosporon causes what disease?

answer

White piedra

question

White piedro is most common in what regions?

answer

Tropical and subtropical zones (associated with poor hygiene).

question

How is white piedra diagnosed?

answer

The nodules are not as discrete and not as dark as those found in black piedra. Microscopically, septate hyphae can be seen that develop into arthroconidia. Culture on Sabouraud's agar without cyclohexamide for 2-4 weeks at room temperature.The colonies appear rough, membranous, white to light or tan colonies.

question

How is white piedra treated?

answer

Shaving, topical azoles.

question

How do dermatophytes grow on skin and other superficial structures?

answer

They possess keratinase, an enzyme which allows them to utilize keratin as a nutrient and energy source.

question

What is the infection of keratinized structures?

answer

Ringworm or tinea

question

What are the three genera of fungi that cause tinea?

answer

Trichophyton, Epidermophyton, Microsporum

question

Is there an inflammatory response to the organisms that cause ringworm?

answer

Yes

question

What are the three categories of organisms causing ringworm/tinea?

answer

Geophilic: normally live in soil, occassional pathogens of animals and humans. Zoophilic: primarily parasitize the body surfaces of animals but can be transmitted to humans. Arthropophilic: generally infect humans and are transmitted between individuals via close human contact, sharing items (clothes, combs, brushes, towels, bed sheets), and crowded living conditions.

question

Name and describe the disease caused by Trichophyton rubrum and Trychophyton mentagrophytes.

answer

Tinea pedis (athletes foot)- scaling, maceration, and itching between the toes.

question

How is tinea pedis transmitted?

answer

Transmitted via the feet by desquamated skin scales in substrates like carpet.

question

Name and describe the disease caused by trichophyton rubrum and Epidermophyton floccosum.

answer

Tinea cruris- jock itch; infection of teh groin seen mainly in men. Lesions are sharply defined with erythematous borders with a normal appearance in the middle.

question

What is the disease most commonly caused by Microsporum canis?

answer

Tinea capitus (scalp ringworm)

question

What are the diseases that are commonly caused by trichophyton rubrum?

answer

Tinea pedis, tinea cruris, tinea corporis, and tinea unguium.

question

What disease is also called dermatophyte onychomycosis?

answer

Tinea unguium

question

How are cutaneous mycoses diagnosed?

answer

Scrapings from clinical specimens. 10% KOH and calcofluor white; will see filamentous hyphae. Some fluoresce with Wood's lamp. Can culture on Sabouraud's media and grow 1-3 weeks.

question

What is the treatment for cutaneous mycoses infection?

answer

Topical azoles or oral terbinafine.

question

What are subcutaneous mycoses?

answer

Chronic, localized infections of the epidermis and adjacent connective tissue and lymphatics following traumatic implantation of the organism.

question

Are subcutaneous mycoses transmissible?

answer

No

question

Causative fungi of this type of infection are all soil saprophytes.

answer

Subcutaneous mycoses

question

What disease is usually caused by Fonsecaea, Phialophora, Cladosporium, and Rhinocladiella?

answer

Chromoblastomycosis

question

What occurs in chromoblastomycosis?

answer

First, small elevated itchy patches appear. New patches appear over subsequent months, becoming reddish purple and hard. Next, rough, warty, cutaneous nodules appear (raised 1-3 cm above skin surface; resemble the florets of cauliflower). These nodules may block lymphatic system and cause elephantiasis. Sometimes a bacterial infection can cooccur and cause systemic illness.

question

How is chromoblastomycosis diagnosed?

answer

Scrapings from surface lesions with 20% KOH. Sclerotic bodies usually easily seen. Dematiaceous thick walled yeast cells are seen. Non-budding but multiplane septation. Can be cultured on Sabouraud's agar for 4-6 weeks at 37 degrees; colonies appear dark and velvety.

question

How is chromoblastomycosis treated?

answer

Terbinafine or azole; heat to shrink lesions. Antifungals not always effective.

question

Chromoblastomcosis normally occurs in what regions?

answer

Tropics or subtropics

question

Name and describe the disease caused by Sporothrix schenckii.

answer

Lymphocutaneous sporotrichosis- caused by dimorphic fungus. Chronic infection involving cutaneous, subcutaneous, and lymphatic tissue. Primary fixed cutaneous lesion at site of injury are small papules most often occurring on an extremity. Lymph nodes become sequentially infected as organisms are swept along the lymph channels. Nodes become enlarged, firm, and discolored. Dissemination is limited to immunocompromised patients.

question

What disease is also called Rose Gardener's disease?

answer

Lymphocutaneous sporotrichosis; known to grow on roses, woody plants, and rich organic soil. Most cases are traced back to plant materials penetrating the skin.

question

Lymphocutaneous sporotrichosis is normally found where?

answer

Tropical and subtropical (although may be found worldwide). Most common in Mexico; endemic in Brazil, Uruguay, and South Africa.

question

How is lymphocutaneous sporotrichosis diagnosed?

answer

Direct microscopy: sparse yeast cells, asteroid body also seen with other infections. Culture of pus or tissue: 2-5 days. Subculture mold, growth as yeast at 37 degrees. Exoantigen test.

question

How is lymphocutaneous sporotrichosis treated?

answer

Azole

question

Name and describe the disease caused by Madurella, Exophiala, Phaeoacremonium, Fusarium.

answer

Eumycotic mycetoma- progressive, tumor-like disease of the hand or foot due to chronic fungal infection; may lead to loss of a body part. Appears in tissue as grainy and characteristic pus production. Lesions progress from subcutaneous swelling to infecting and destroying deeper tissue, muscle, fascia, and bones. Remains localized to limb. Traumatic implantation- noncontagious. The subq swelling is hard and swelling; ruptures near surface and infects deeper tissues.

question

How is eumycotic mycetoma diagnosed?

answer

Recover granules- black, red, or white. Microscopy with 20% KOH. 2-6 micrometers are fungal, less than .5 micrometers are actinomycetes. Culture with penicillin.

question

How is eumycotic mycetoma treated?

answer

Terbinafine and amputation

question

Name and describe the disease caused by Exophiala, Wangiella, Bipolaris, Curvularia, and Alternaria.

answer

Subcutaneous Phaeohyphomycosis- subcutaneous cysts on feet, legs, and other body sites; usually painless. Can also cause brain and nasal sinus infections. Found in soil and plant debris->traumatic entry.

question

How is eumycotic mycetoma diagnosed?

answer

Excision of cysts: fibrous cysts and central necrosis. Pigmented fungal elements. The tissue morphology of the causative organism is mycelial.

question

How is eumycotic mycetoma treated?

answer

Surgery

question

Name and describe the disease caused by Basidiobolus ranarum.

answer

Basidiobolomycosis- normally found in children. Traumatic implantation, moveable masses on various parts of the body. Lesions may ulcerate.

question

What two diseases are considered to be subcutaneous zygomycosis?

answer

Basidiobolomycosis and Conidiobolomycosis

question

Name and describe the disease caused by Conidiobolus coranatus.

answer

Conidiobolomycosis- found in young adults most often; swelling of the face, firm and painless. Caused b/c of inhalation.

question

Subcutaneous zygomycosis is diagnosed how?

answer

Clinical features and biopsy (hyphae surrounded by eosinophils).

question

How is subcutaneous zygomycosis treated?

answer

Azoles

question

Give three examples of systemic mycoses.

answer

Histoplasmosis, coccidioidomycosis, and blastomycosis.

question

What is the route of acquisition of systemic mycoses?

answer

Inhalation of spores of dimorphic fungi that have their mold forms in the soil.

question

What occurs when systemic mycoses spores are inhaled into the lungs?

answer

The spores differentiate into yeasts.

question

Do persons infected with systemic mycoses communicate the diseases to other?

answer

No

question

Where is histoplasmosis commonly found?

answer

Distribution is worldwide, but it is most prevalent in eastern and central regions of the US (Ohio, Mississippi, Kentucky). AKA Ohio Valley Fever

question

What kind of environment is Histoplasma capulatum most commonly found?

answer

Moist soil high in nitrogen content (bat and avian habitats).

question

Describe histoplasmosis.

answer

Inhaled conidia convert to budding yeast cells. They are phagocytized by alveolar macrophages; they then produce alkaline substances that raise the pH and inactivate the degradative enzymes of the phagolysosome. Acute pulmonary histoplasmosis: flu-like symptoms, fever, chills, headache, patchy pulmonary infiltrates. Disseminated histoplasmosis develops in a minority of infected persons (anorexia, fatigue, oral ulcers, hepatosplenomegaly).

question

How is histoplasmosis diagnosed?

answer

Direct examination->yeast cells within macrophages. During culture, the mold turns to yeast. Exoantigen test, nucleic acid test, patient antibodies, antigen in urine or serum.

question

What is the treatment for histoplasmosis?

answer

Usually self-limiting infection. Azole or amphotericin B.

question

Where is coccidioidomycosis usually found?

answer

Found in alkaline soils in semiarid, hot climates; endemic to SW US and Latin America.

question

Describe the morphology of the organism that causes coccidioidomycosis.

answer

Distinctive morphology; blocklike arthroconidia in the free-living stage and spherules containing endospores in the lungs. *arthrospores are very light and are carried by the wind and inhaled from dust.

question

Describe coccidioidomycosis.

answer

Frequently asymptomatic, primarily pulmonary disease with flu-like symptoms, fever, cough, chest pain. Usually self-limiting. May be accompanied by a erythematous macular rash. Progressive pulmonary disease. May become a disseminated disease to almost any organ (meninges, bone, skin). It is a defect in cell-mediated immunity.

question

How is coccidioidomycosis diagnosed?

answer

Direct examination of spherules in sputum: sputum (use 10-20% KOH with calcofluor white) or tissue (use H&E). Culture not necessarily done b/c highly infectious. Patient antibodies.

question

What is the treatment for coccidioidomycosis?

answer

Not needed in many cases. Amphotericin B or azoles.

question

Where is blastomycosis normally found?

answer

Free-living species distributed in soil of a large section of the Midwestern and Southeastern US.

question

How is blastomycosis contracted?

answer

Inhaled conidia convert to yeast and multiply in lungs.

question

Describe blastomycosis.

answer

Primary pulmonary disease; frequently asymptomatic and self-limiting. Flu-like symptoms, fever, cough, chest pain. Disseminated disease to skin, bone, CNS, spleen. Chronic cutaneous disease: dissemination from lungs. Single or multiple ulcerating lesions of face, neck, scalp, and hands.

question

How is blastomycosis diagnosed?

answer

Direct examination of budding yeast; culture: mold growth at 25-30 degrees. Converts to yeast at 37 degrees. Exoantigen test, nucleic acid test.

question

What is the treatment for blastomycosis?

answer

Amphotericin B or azole

question

What are three examples of opportunistic fungal infections?

answer

Candidiasis, cryptococcosis, and aspergillosis.

question

Where is candida albicans normally found?

answer

Widespread yeast; normal flora of oral cavity, genitalia, large intestine, and skin of humans. Causes primarily endogenous infections.

question

Describe infections that can be caused by candida albicans.

answer

Can be short-lived superficial skin irritations to overwhelming, fatal systemic diseases. Thrush- thick, white, adherent growth on the mucus membrane of mouth and throat. Vulvovaginal yeast infection- inflammatory condition of the female genital region that causes itching and a white discharge. Cutaneous candidiasis- occurs in chronically moist areas of the skin (diaper rash). Chronic mucocutaneous candidiasis (CMC)- defect in T-cell mediated immune response (lesions fail to heal). GI infection, UTI, hematogenous infection (eyes, bones, joints, brain, CNS, endocarditis).

question

How is candidiasis diagnosed?

answer

Direct examination: budding yeast cells and budding pseudohyphae. Growth on CHROMagar; differentiates Candida species.

question

How is candida treated?

answer

Topical azoles for superficial infections; amphotericin B or azoles for systemics.

question

Where are organisms found that cause cryptococcosis?

answer

Widespread, found in soil, especially with bird droppings.

question

Describe cryptococcosis.

answer

Frequently asymptomatic, pulmonary symptoms include cough, fever, and lung nodules. Dissemination causes lesions on skin, eyes, and bone. Most common disease is meningitis. Slow onset with nonspecific symptoms (headache, irritability, dizziness) appear over a few weeks or months. May also see behavioral changes, fever, seizures, dementia and decreased levels of consciousness. Can be fatal if not treated.

question

How is cryptococcosis diagnosed?

answer

Direct microscopy via india ink stain/gram stain. Appear as mucoid colonies after 3-5 days of culture. Biochemical tests: phenol oxidase and urease. Capsule antigen in serum or CSF (rapid, sensitive, specific).

question

What is the treatment for systemic cryptococcosis?

answer

Amphotericin B and fluconazole for 2 weeks, with azole for 8 weeks.

question

Describe aspergillosis.

answer

Allergic aspergillosis: asthma, cough, fever, nasal obstruction, headache, discharge, facial pain, pulmonary infiltrates. Pulmonary aspergillosis- underlying pulmonary disease. Aspergilloma- fungus ball. Usually no tissue damage, so no treatment is needed. If hemorrhage occurs, surgery is needed. Invasive pulmonary aspergillosis- only in immunocompromised patients or underlying pulmonary disease. Invasion into tissue by hyphae. Fever, pulmonary infiltrates, chest pain, coughing up blood. Disseminated aspergillosis- infection of brain, heart, liver, spleen.

question

How is aspergillosis diagnosed?

answer

Direct examination, large branching septate hyphae. Culture on mycolic media without cyclohexamide Detection of antigen in serum. Treatment includes amphotericin B or azole.

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