Lesson 3.1.1

• Superficial Mycoses


  • fungal infections of the skin and the hair
  • causes little or no inflammatory or immunologic reactions
  • pityriasis versicolor, tinea nigra, black piedra, and white piedra
• Pityriasis/Tinea versicolor


  -infection of stratum corneum

  -acquired person to person

  -hyper/hypo pigmentation of the skin

  -normal flora

  -cause disease when yeast form transforms to mycelial form

  -lipophilic fungus
• causative agent of Pityriasis Versicolor

  Malassezia furfur (Pitysporum orbiculare)
• Pityrosporum folliculitis


  -Pruritic follicular papules and pustules

  -Inflammation caused by excessive growth of M. furfur and M. globosa
• Related diseases of Pityriasis/ tinea versicolor

  • Pityrosporum folliculitis
  • Seborrheic dermatitis
  • Atopic dermatitis
  • Neonatal cephalic pustulosis
• Lab Diagnosis of Pityriasis/ Tinea versicolor

  1. Wood's Light: bright yellow flourescence
  2. KOH: hyphal and yeast form with spaghetti and meatballs appearance (Pityrosporum folliculitis: only yeast form)
  3. Culture: SDA or malt agar (covered with a layer of olive oil and may contain streptomycin penicillin and actidione)
• Tinea Nigra


  -brown to gray-green macule or patch that can be velvety

  -brownish spot on the palm, sole, neck or trunk

  -spreads centrifugally and darkens

  -found in soil, sewage, bathrooms (environmental pathogens)

  -no human-to-human transmission
• Causative agent of Tinea Nigra

  Hortaea (Phaenellomyces/Exophiala) werneckii
• Laboratory Diagnosis of Tinea Nigra

  1. KOH:

  • Septate, dematiaceous (brownish or olive) hyphae
  • Single or paired oval to spindle-shaped yeast cells
  • 2. Culture: SDA
  • Moist, black, yeast-like coloniea
  • older cultures have aerial hyphae (fuzzy, grayish black)
• Piedra

  • infection of the hair shaft
  • means stone
  • fungi adhere to hair and form nodules along the hair shaft
• Black Piedra

  Causative agent: Piedraia hortae
• Black piedra


  -mark of beauty in Pacific

  -Found in soil (environmental)

  -no human-to-human transmission

  -infects scalp and hair (pubic region)

  -gritty, hard, brown-black granule, adherent/firm
• Lab Diagnosis of Black Piedra

  1. KOH crush prep (Dematiaceous hyphae with asci and 8 ascospores)
  2. Culture: SDA (slow-growing dark green/ brown/ black colonies)
• White Piedra

  Causative agent: Trichosporon beigelli
• White Piedra

  -environmental: soil, stagnant water, decaying fruit, spoiled food

  -occasional skin flora: groin and axilla

  -bearded regions

  -softer, white/red/green/light brown granules
• Lab Diagnosis of White Piedra

  • KOH crush prep (non-dematiaceous hyphae with blastoconidia and arthroconidia)
  • Culture: SDA (moist, cream-colored, yeast-like colonies and inhibited by cyclohexamide)