Micro: Fungal Infections Flashcards
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
- Trichophyton
- Microsporum
- 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.
