Dermatomycoses and subcutaneous fungi infections

Question 1

What are the 3 most common dermatophytes?

What form do they grow in? (mold or yeast)

Answer 1

Microsporum

Epidermophyton

Trichophyton

They are all molds exclusively

Question 2

How are dermatophytes cultured?

Answer 2

On Sabourauds agar,

with cycloheximide and chloramphenicol, gentamycin.
it is acidic
contains glycose and peptone.

Question 3

What are the dermatophyte infections called clinically, on different body parts?

Answer 3

Tinea corporis - anywhere else on the body.
Tinea crusis - in the crotch
Tinea pedis - foot
Tinea capitis - head, hair loss, usually in children
Tinea unguium - on the nails

Question 4

Malassezia furfur,

disease, clinical presentation, transmission

Answer 4

• disease: Ptyriasis Versicolor
• hypo or hyperpigmentation patches of skin.
• no other symptoms
• in Infants with TPN, can cause severe sepsis and thrombocytopenia,
• may also cause a more mild form of this in immunocompromised adults receiving high-lipid content IV infusions.

Question 5

How are dermatophyte infections stained or observed?

Answer 5

KOH prep, which dissolves other tissues/kertain and leaves behind the fungus.

Observation under Wood’s lamp in a dark room, Golden fluorescence.

Question 6

Treatment for Ptyeriasis Versicolor?

Answer 6

topical selenium sulfide/selsin blue

Question 7

What is the fungus that causes the most clinically significant subcutaneous mycosis?

Answer 7

Sporothrix schenckii,

it spreads rapidly, via lymphatics and causes red, raised, intra-dermal sores along the lymph chain visible on the skin

the sores are initially granulomatous nodules, then become necrotic

Question 8

How is subcutaneous mycosis transmitted?

How do they survive in the subcutaneous tissue?

Answer 8

via traumatic implantation, of the fungus from a scratch by a fungus covered thorn or branch on a plant.

release proteolytic enzymes, and generate a microaerophilic environment by lowering the redox potential of the local tissue.

Question 9

What is chromoblastomycosis?

How is it transmitted?

What fungi cause it?

Answer 9

It is a slowly progressing, chronic subcutaneous fungal infection, occurs mainly in tropical regions.

The lesions are cauliflower wart-like, and become very large over months/years. They are difficult to treat with drugs, but itraconazoles are the choice. Surgical excision is best option.

Rarely, elephantiasis may occur from fibrosis of the lymphatics, related to secondary infections

traumatic implantation.

Phialophora verrucosa
Cladosporium carrionii
Fonsacaea pedrosoi