Superficial & Cutaneous Mycoses

• Malassezia infections:

  • Causative agent of Pityriasis versicolor / Tinea versicolor
  • Discoloration or depigmentation of skin
  • Chronic superficial infection of stratum corneum
  • Caused by species of lipophilic yeast (Malassezia)
  • Majority of cases caused by Malassezia furfur complex, Malassezia globosa, Malassezia sympodialis, Malassezia restricta
  • Causes seborrheic dermatitis or dandruff
  • Treatment: Ketoconazole
  • Microscopic Examination:
  • Short unbranched, non-pigmented hyphae, spherical cells
  • "Spaghetti and meatballs fungus"
  • Macroscopic Examination:
• • Malassezia Infection
  • Macroscopic exam: Cream-colored, moist and smooth
  • Treatments:
  • Anti-dandruff shampoos
  • Selenium sulfide (daily application)
  • Topical or oral azoles
  • Ketoconazole
  • Medium used: Requires lipid for growth, overlaid with olive oil
  • Diagnosis to confirm: Direct KOH (10-20%), Stained with calcofluor white
• Piedra:

  • Latin word for hair shaft
  • Nodules composed of hyphae and cement-like substance
  • May infect hair of axilla, genitalia, beard, and scalp hair
  • Black Piedra caused by Piedraia hortae
  • Hard, dark brown to black gritty nodules
  • Nodules consist of asci with 8 ascospores
  • To confirm: 10% KOH for skin, hair, 20% KOH for nail
  • Medium: SDA, brown, restricted colonies with dark brown metallic green tinge
  • White Piedra caused by Trichosporon spp.
  • Soft mycelial mat surrounding scalp hair, face, and pubic region
• • Most common Trichosporon: Trichosporon asteroids, Trichosporon asahii, Trichosporon mucoides
  • Laboratory diagnosis: arthroconidia, hyphae, blastoconidia
  • Colonies: straw to cream colored and yeast-like
  • Biochemical reactions: Absence of carbohydrate fermentation, (+) Potassium Nitrate, (+) Urease
  • Treatment: 1:200 solution of bichloride mercury, 3% sulfur ointment, Benzoic acid and Salicylic acid
• Tinea Nigra:

  • Brown or black macular patches and non-scaly macules
  • Primarily on palms and soles of feet
  • Caused by Hortaea werneckii
  • Laboratory diagnosis: Skin scrapings with 10-20% KOH, shiny, moist, yeast-like colonies on SDA
  • Treatment: Keratolytic solutions, Salicylic acid, Azole antifungal drugs
• Dermatophytes:

  • Fungal diseases of keratinized tissues
  • Ringworm: inflammation at advancing margin of lesion
  • Genera: Trichophyton, Microsporum, Epidermophyton
  • Keratinophilic: hair, nails, cutaneous layers containing keratin
  • Classified as Geophilic (soil), Zoophilic (animals), Anthropophilic (human host)
  • Medium used: SDA, Mycosel medium, Mycobiotic medium
  • Asexual conidia and sexual conidia for reproductive cells
  • Various forms of dermatophytoses and respective affected sites
• Trichophyton rubrum:

  • Foot and toenail infection
  • Lesions: clear center with red margin
  • Typical microscopic picture with clavate or peg-shaped microconidia
  • Macroscopically: cottony and white colonies, later becoming velvety
  • Microscopically: macroconidia pencil-shaped, microconidia tear drop/pear-shaped
• Infections involving the nails:

  • Tinea unguium (Onychomycosis): terbinafine or itraconazole treatment
  • Trichophyton rubrum, T. mentagrophytes, T. tonsurans, Epidermophyton floccosum
• Trichophyton mentagrophytes:

  • Athlete's foot, Tinea capitis, Tinea corporis, Tinea barbae, Tinea cruris
  • Hair: ectothrix
  • Microconidia primarily globose, may appear tear-shaped
  • Macroconidia thin-walled, smooth, cigar-shaped with four to five cells
  • Spiral hyphae
  • Granular colonies when abundant microconidia are formed
• Tinea Pedis:

  • Common disease affecting soles of feet and toe webs
  • In severe cases, extensive scaling, fissuring, erythema
  • Progression to moccasin foot
• Infections involving the hair:

  • Trichophyton schoenleinii: Tinea favosa, crusty lesion with scutula
  • Microsporum audouinii and Microsporum ferrugineum: gray patch ringworm, black dot ringworm
  • Trichophyton tonsurans and Trichophyton violaceum: Black dot ringworm, brittle hair shafts
  • Trichophyton tonsurans: round peg-shaped microconidia, balloon appearance, rust-colored pigment on colony's reverse
  • Microsporum gypseum: Geophilic, Tinea barbae, Ectothrix, cinnamon color colonies
• Growth on rice grains:

  • Dermatophytes grow well on rice grains, M. audouinii turns grains brown
• Epidermophyton floccosum:

  • Macroconidia club-shaped
  • Colonies yellow to yellow-tan, flat with feathered edges
  • Hair perforation test and Urease test for differentiation
• Hair perforation test: Sterile 5- to 10-mm hair fragments are floated on sterile water

  supplemented with a few drops of sterile 10% yeast extract.

  • Used to distinguish dermatophytes
  • T. rubrum causes surface erosion, T. mentagrophytes forms perpendicular penetration pegs
  • Urease test: T. mentagrophytes produces urease, T. rubrum may be negative or delayed reaction
• Superficial mycoses is a non-invasive infection that affect the outer layer of the skin
• Malassezia furfur complex deletion using Wood’s lamp/ light, which fluoresce yellow color
• Malassezia furfur complex

  spores: Blastospores

  hyphae: Rhizoids

  Pigment: Hyaline

  cross walls: Coenocytic
• 10% KOH: Smear digesting agent
• Black piedra: greenish to black with raised center

  spores: ascospores

  shape: rhizoid

  pigment: dematiaceous

  Crosswalls: septated
• Trichosporon spp. are soft yellow/ pale brown aggregation around the hair shaft/ axillary, facial, genital, & the scalp.
• Trichosporon ovoides and Trichosporon inkin are common Trichosporon spp. That affects facial and genital hairs
• White piedra

  Spore: Arthrospore

  shape: rhizoid

  pigment: hyaline

  crosswalls: septated
• Tinea nigra or Tinea nigra palmaris is a superficial chronic & asymptomatic infection of the stratum corneum.
• Trichophyton: skin, hair, nail
• Microsporum: skin and hair
• Epidermophyton: skin and nail
• characteristics of dermatophytic fungi that are produced by thallic conidiogenesis: macronidium or micronidium
• Tinea capitis: Head

  Tinea favosa: Head (distinctive pathology)

  Tinea barbae: beard

  Tinea corporis: body (glabrous skin)
• Tinea manuum: Hand

  Tinea unguium: Nails

  Tinea cruris: Groin

  Tinea pedia: feet

  Tinea imbricate: body (distinctive lesion)
• Tichophyton rubrum do not fluoresce on wood’s lamp/ light
• Tinea unguium (onychomycosis) relapses are common; toenail infection
• Hair perforation test

  Trichophyton rubrum: (-)

  Trychophyton mentagrophytes: (+)
• Trichophyton schoenleinii: ringworm of the scalp

  hyphae do not form the spores but can be found within the hair shaft
• Scutula are crusty, cup-shaped flakes
• Microsporum audouinii is a non-inflammatory infection of the scalp & skin especially in children. Microcopically: racquet hyphae/ favic chandelier
• Microsporum canis: tinea capitis in human; spindle-shaped, with echinulate, thick walls, and has 6 or 8 to 15 cells. Colonies are fluffy & white, with reverse side of the colony usually developing a lemon yellow/rich canary yellow pigment, especially on potato dextrose agar