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Flashcards in Micro: Fungal Infections Deck (18):

Causative agent of Pityriasis versicolor

Malassezia furfur


Component required for M. furfur to grow.

Long Chain fatty acids
-growth also stimulated by increased body temp, humidity, greasy skin, sweating


Presentation of Pityriasis versicolor

Hypo or Hyperpigmented skin patches concentrated in regions with a high amount of sebaceous gland


2 methods to diagnose Pityriasis versicolor

Woods Lamp: bright yellow fluorescence
KOH prep: unbranched hyphae w/ round spores (spaghetti and meatball appearance)


Causative agent of Tinea nigra

Hortae werneckii


Pathogenesis of Tinea nigra

Fungal cell growth of Hortae werneckii in the epidermis induces melanin production from melanocytes causing a brownish gray path on palms or soles


Pathogenesis of White Piedra

Superficial infection of Trichosporon sp. causing white nodules to form on facial, axillary, and pubic hair.


Complication of Trichosporon infection

Endocarditis (prosthetic or IV drug user vavles)
CNS infections


Pathogenesis of Black Piedra

Superficial infection of Piedraia hortae. Forms an Ectothrix (black stone-like formation) on scalp and facial hair.


3 causative agents of Dematophytoses.

AKA ringworm or Tineas
1. Trichophyton
2. Microsporum
3. Epidermophyton


Presentation of the Dermatophytoses.

Athlete's foot, jock itch, slap infection, nail infection
-lesions have a curved border and resemble a worm
(hyphae form in stratum corneum, deeper spread restricted by higher body temperature)


Pathogenesis of Dermatophytoses

Fungus has keratinases (virulence factor) that degrades keratin and allows the fungal to grow and spread. A delayed hypersensitivity reaction induced by the host CMI causes inflammation and itching


Most common cause of Tinea pedis, cruris (jock itch), corporis

Trichophyton rubrum


How is Tinea cruris differentiated from Erythrasma?

Erythrasma fluoresces coral red and is caused by Corynebacterium minutissimum

T. cruris does not fluoresce


How is Tinea cruris differentiated from Candida a.?

Candida affects the skin on the scrotum and thigh
Tinea cruris is mainly just the skin on the thigh adjacent to the scrotum


Main causative agent of Tinea capitis

Trichopyton tonsurans
(Microsporum can also cause it, differentiate with Wood Lamp)


Pathogenesis of Onychomycosis.

Fungal infection of the nail.
-caused by dermotophytes, Candida, some non-dermatophytes
-a secondary rash forms caused by a host inflammatory response


Pathogennesis of Drunken Rose Gardener Disease

Break in the outer skin layers allows infection by Sporothrix schenkii
-the fungus infects local tissue causing papule formation
-eventually the fungus can spread by lymphatic channels forming a line of nodules and in IC patients it can disseminate thru the body.