Medical Mycology:Superficial, Cutaneous and Subcutaneous Mycoses

Hugh B. Fackrell

Mycoses & Mytoxicosis

• Mycoses: fungal infections

• Mytoxicosis: intoxicaton

Fungal Disease

• Mycoses Colonization of the host

• Mycotoxicosis: Intoxication

• Hypersensitivity

Fungal Entry

• Rarely cause disease in healthy person

• Commensal
  • Candida albicans
  • Malasseza fufur

• Underlying disorder
  • trauma
  • immunological deficiency
  • debilitating conditions

Disease Mechanisms of Fungi

Endogenous

• Opportunistic

• Iatrogenic
  • (physician induced)
  • e.g. indwelling lines catheters

Exogenous

• Opportunistic
  • inhalation

• Superficial
  • Trauma hygiene

• Cutaneous
  • trauma

• Subcutaneous
  • trauma

• Systemic
  • inhalation

Fungal Dissemination

• Breach in host defenses
  • endocrinopathies
  • immune disorders
  • iatrogenic

• Must repair defect

Host Defense Factors

• Intact skin

• long chain fatty acids

• pH

• Bacterial antagonism

• corneum stratum desiccated

• epithelial cell turnover rate (0.5 kg/yr.)

• Mucous membranes

• ciliated

• antimicrobials

• Immunological competence

Fungal Infections

• Opportunistic Infections

• Superficial fungal infections

• Cutaneous Mycoses

• Subcutaneous Mycoses

• Systemic Mycoses

Structure of Skin

Superficial Fungal Infections

• Skin Infections
  • limited to Stratum corneum
  • do not penetrate deeper tissues

• No inflammation

Superficial mycoses

• Pityriasis versicolor

• Black piedra

• White piedra

• tinea nigra

Black Piedra

• Superficial mycosis

• Piedraia hortai

• small firm black nodule

• Surrounds hair shaft

White Piedra

• Superficial mycosis

• Trichasporon beigelii

• soft friable beige nodule

• distal ends of hair shaft

Pityriasis Versicolor

• Common superficial mycosis

• Superficial keratin layer

• hypo or hyper pigmentation on skin of neck shoulders chest and back

Malassezia furfur

Malassezia furfur

Tinea Nigra

• Superficial mycosis

• Phaeoannellomyces werneckii

• silver nitrate type of stain

• palm of hand

Cutaneous Mycoses

• Dermatophytoses

• Dermatomycoses

Dermatophytoses

• Cutaneous Mycoses

• Secrete keratinolytic enzymes which dissolve the skin protein KERATIN

• Three genera
  • Epidermophyton.
  • Microsporum,
  • Trichophyton

• Anatomic specificity correlates with genus
  • -skin,hair,nails.

Epidermophyton

Microsporum

Microsporum

Ectothrix

Spores on outside of hair follicle

Microsporum

Microsporum

Microsporum

• Spores of Microsporum lie outside the hair shaft. This is known as ECTOTHRIX

• Can be seen with an ultra violet lamp called a “Woods” light. Bright fluorescence.

• Children are more susceptible than adults, because post pubertal sebum has fungistatic fatty acids especially M.audouinii

Microsporum audouinii,canis

M.audouinii -Predominant species in temperate climates.

Very contagious can cause epidemics

Spread by barbers tools, seat head rests

M.canis- Second most common- spread by kittens, pups - young animals

Trichophyton

Trichophyton

Trichophyton

Trichophyton

Dermtaophytes:Tinea Infections

• Tinea capitis - Head, scalp, neck

• Tinea barba - Face

• Tinea corporis - Body

• Tinea.cruri - Groin, perineum

• Tinea pedis - Feet

• Tinea unguium -Nails

TINEA means RINGWORM

Tinea capitis

Ringworm of the scalp-very contagious- especially pre-pubertal children.

Begins with small, itchy, scaling papule

spreads peripherally makes a roundish lesion,

Hair breaks off at scalp level, leaving a patch.

Tinea Capitis

PPT Slide

Tinea corporis

• Ringworm of the body,with annular lesions the centre is scaly and the periphery advancing circle of vesicles and papules.

• Prefers areas that are hairy soon to become bare due to the fungus.

• Associated with poor nutrition and hygiene but is also common in persons who frequent gymnasiums and pools.

PPT Slide

Tinea pedis

Tinea pedis - “Athletes foot”skin cracks between toes, maceration of tissue,desquamation, ulcerations, can spread whole bottom foot.

Epidermophyton and Trychophyton. ~ 2% carry fungus no symptoms.men susceptible

Tinea Pedis

PPT Slide

Tinea cruris

T.cruris- Groin, perineum,perianal region Epidermophyton floccosum or inguinale. Tight pants,perspiration,pubic contact.

Epidermophyton and Trychophyton. ~ 2% carry fungus no symptoms.men susceptible

Tinea Cruris

Epidermophyton

Tinea unguium

Nails brittle thick,discoloured, grooved.

Trichophyton rubrum most common in women aged 40-50

Persistent very difficult to treat. Antibiotics cannot be effective.

PPT Slide

Dermatomycoses

• Cutaneous fungal infections

• inflammation

• caused by opportunistic fungi

• Candida spp

Cutaneous Mycoses:Treatment

• Mild cases topical treatment

3% sulfur+3% salicylic acid ointment

1% crystal violet

1% iodine

1% tolnaftate

10% undecylenic acid

miconazole haloprogin

Cutaneous MycosesTreatment

• Serious or stubborn cases

Griseofulvin - 1gram /day for 1-3 months

This antimicrobial extracted from cultures of Penicillium griseofulvum in 1939 not used as a drug until 1959

Subcutaneous Mycoses

• Caused by trauma [puncture]and introduction of the fungus and bacteria.

• Chromoblasomycosis

• Phaeohypomycosis

• Mycetoma

• Sporotrichosis

Chromoblastomycosis

• Subcutaneous mycosis

• verrucoid skin lesions

• lower extremities

• Histology

• muriform cells- cross walls in two directions

• no involement of bone tendon or muscle

PPT Slide

PPT Slide

Phaeohypomycosis

• Infections caused by dermatiaceous fungi

• hyphal to yeast forms in tissue

• Dermatiaecous Fungi
  • melanin black fungi

Mycetoma

• Granulomatous local lesions
  • usually of the legs and feet
  • infect humans who have extensive contact with soil and foliage due to bare feet and legs.

• Suppuration
  • small visible pigmented grains or granules
  • microcolonies

• Destroys bone tendon and muscle

Mycetoma

• caused by many organisms

• Eumycotic mycetoma
  • fungal
  • USA Pseudallescheria boydii

• Actinomycotic mycetoma
  • bacterial
  • USA Nocardia brailiensis

• Madura foot

Sporotrichosis

• world wide-Sporothrix schenkii

• ulcerative lesions at site on injured skin usually arm, spread to the regional lymph nodes. The high risk group, gardeners, farmers who work with wood/ soil.

• Highly infectious on contaminated dressings to patients with wounds.

Sporotrichosis

Sporotrichosis

Sporotrichosis

Treatment of sporotrichosis

• topical potassium iodide
• amphotericin B systemically.