superficial fungal infection

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SUPERFICIAL
AND
SUBCUTANEOUS MYCOSES

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SUPERFICIAL AND SUBCUTANEOUS MYCOSES

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SUPERFICIAL MYCOSES
Surface Infection:
• Fungi lives on dead
layers of skin and
its appendages
• No inflammatory
response
• Examples:
• Tinea versicolor
• Tinea nigra & Piedra
Cutaneous Infections:
• Confined to cornified
layers of skin and its
appendages
• Inflammatory and
allergic responses
are induced
• Examples:
• Dermatophytosis
• Candida infection of
skin

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PITYRIASIS VERSICOLOR
• Chronic asymptomatic mainly in young adults
• Involves Stratum corneum
• Caused by Malassezia furfur (Pityrosporum
orbiculare)
• Macular depigmentation of skin of chest,
abdomen, upper limbs and back
• Skin scrapings shows yeast like cells, short
branched filaments
• Grows on Sabouraud agar covered with olive
oil

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TINEA NIGRA
• Black or brownish macular lesions on palms
• Involves stratum corneum
• Caused by Exophiala werneckii
• Skin scrapings brownish septate hyphae and
budding yeast cells
• Grey or black colonies on Sabouraud agar

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PIEDRA
• Fungal infection of hair
• Firm irregular nodules along the hair shaft
• Black Piedra: caused by Piedraia hortae
• White Piedra: caused by Trichosporon beigelii

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DERMATOPHYTOSES
• Infection of keratinised structures of skin,
hair and nail
• Caused by a group of keratinophilic fungi
• Dermatomycosis: Skin lesions produced by
other fungi such as Candida albicans and
cutaneous manifestation of systemic
mycoses

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CHARACTERISTICS OF DERMATOPHYTES
• Filamentous fungi, Digests keratin
• Does not invade living tissues
• Belongs to three genera Trichophyton,
Microsporum and Epidermophyton
• Mode of infection is by direct contact with
Fungus from Humans– Anthropophilic,
Animals –Zoophilic and soil – Geophilic.
• Resistant to Cycloheximide

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DERMATOPHYTOSES
Clinical types of dermatophytoses and their common causative agents

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LAB DIAGNOSIS OF DERMATOPHYTES
• Specimen: Skin—Scrapings, Nail---Clippings
Hair---Plucked from scalp (Fig. 63.3)
• Microscopy: 10% KOH (Potassium hydroxide)
• Branching and septate hyphae, spores (Fig.
63.2)
• Culture: Sabouraud Dextrose Agar (pH 5.4)
• With Chloramphenicol and Cycloheximide
• Morphology studies with LPCB (Lacto Phenol
Cotton Blue Stain) in a Tease mount

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LAB DIAGNOSIS OF DERMATOPHYTES
Some characteristics of common dermatophytes

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• Table 63.2
• Fig 63.5
Some characteristics of common dermatophytes (Continues)

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TRICHOPHYTON

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Characteristic macroconidia

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 Mycotic mycetoma
 Chromomycosis
 Sporotrichosis
 Rhinosporidiosis

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MYCETOMA FOOT
• Chronic, Slow progressive, post traumatic
• Multiple discharging sinuses – Granules
(Table 63.3)
Colour of grains in mycetomas of various origin

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• 3 Types:
Eumycetoma--- Fungi
Actinomycetoma--- filamentous bacteria
Botryomycosis --- Staphylococcus aureus

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LAB DIAGNOSIS OF MYCETOMA FOOT
Specimen: Granules or Grains (micro colonies)
Microscopy:
Actinomycotic: Very thin filaments
Eumycotic: Broader hyphae, septate,
Chlamydospores present
Culture: Sabouraud Dextrose Agar

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CHROMOMYCOSIS
• Verrucous dermatitis –– dematiaceous fungi
Fonsecaea pedrosoi, Exophiala dermatitidis
• Common in barefoot farmers & woodcutters
• Mode of Infection--Traumatic implantation
of fungi
• Warty cutaneous nodules resembling florets
of cauliflower in feet and lower leg --
round irregular dark brown yeast like
bodies with septae --- Sclerotic bodies

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Copper penny bodies

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SPOROTRICHOSIS
• Chronic infection of cutaneous, sub
cutaneous and lymphatic tissues
• Common in gardeners & forest workers
• Caused by Sporothrix schenckii (Dimorphic)
• Cutaneous nodules, Spreads by lymphatics
• Samples: Aspirates, Pus and Biopsy
• Yeast like basophilic body with a ray of
eosinophilic ray --- Asteroid bodies

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LBCB: septate
hyphae with flower
like conidia
Lymphocutaneous
sporotrichosis

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RHINOSPORIDIOSIS
• Chronic granulomatous friable polyps in the
nose, mouth or rarely eye
• Caused by Rhinosporidium seeberi
• Mode of Infection: not known, may be due
to inhalation of spores from stagnant water
• Cannot be cultured in artificial media
• Histopathology shows large number of
fungal spherules containing endospores

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