2. Superficial Mycoses andDermatophytosis Predisposing factors: humidity Immunosuppression Poor hygiene Affects the epidermal area with strong affinity to keratin
96. Dermatomycosis - more general name for any skin disease caused by a fungus. - invasion of the cutaneous tissues by other fungi.
97. THE SKIN PLANTS Etiological agents are called dermatophytes - "skin plants". Three important anamorphic genera, (i.e., Microsporum, Trichophyton, and Epidermophyton), are involved in ringworm. Dermatophytes are keratinophilic - "keratin loving". Keratin is a major protein found in horns, hooves, nails, hair, and skin. - use keratin as a source of nitrogen Ringworm - disease called ‘herpes' by the Greeks, and by the Romans ‘tinea' (which means small insect larvae).
98. Infections by Dermatophytes Severity of ringworm disease depends on (1) strains or species of fungus involved and (2) sensitivity of the host to a particular pathogenic fungus. More severe reactions occur when a dermatophyte crosses non-host lines (e.g., from an animal species to man).
99. Dermatophytes Common Causative agents: a. Microsporum - hair, skin, rarely nails - children, rarely in adults - spontaneous remission b. Trichophyton - hair, skin & nails - both children & adults - chronic. c. Epidermophyton - skin, nails, rarely hair - adults, rarely children
100. Among dermatophytes there appears to be a evolutionary transition from a saprophytic to a parasitic lifestyle. Geophilic species - keratin-utilizing soil saprophytes (e.g., M. gypseum, T. ajelloi). Zoophilic species - keratin-utilizing on hosts - living animals (e.g., M. canis, T. verrucosum). Anthropophilic species - keratin-utilizing on hosts - humans (e.g., M. audounii, T. tonsurans)
103. Microsporum species Common features: Colony: Mycelium: white to buff Underside: yellow to reddish brown Microscopic attached singly thick walls & mature forms are echinulate (spiny) Spindle-shaped macroconidia Septate hyaline hyphae
104. Microsporum gypseum complex Teleomorphs are Arthroderma gypseum and A. incurvatum. Produces abundant macroconidia brownish-yellow due to large numbers macroconidia. Surface of culture colony often is powdery in appearance. Reverse of colony often appears ragged around edges. Macroconidia usually have 4-6 septa or crosswalls, up to 40 µm long Microconidia are smaller than in M. canis. In lactophenol, water is extracted and can cause the macroconidia walls to collapse. This is an artifact due to mounting media. Macroconidia do not form on infected hair!
107. Microsporum canis Teleomorph is an ascomycete called Arthroderma otae. Macroconidia are abundant, thick-walled with many septa, up to 15. Macroconidia are often hooked or curved at ends. Microconidia are small and clavate (club-shaped).
110. Dermatophytosis of the skin Clinical Manifestations: “ringworm” Papules to pustules with clear center and active borders (peripheral pustules and scaling), itchy,circinate and serpiginous with inflammatory, vesicular, enlarging margins Differential Diagnosis: Psoriasis: dry and circinate borders Ezcema: no clear center
124. Epidermophyton floccosum Areas affected: skin and nails Disease: Tinea cruris or “jock itch” Often start on the scrotum and spread to the groin as dry, itchy lesions Source of infection: Sharing of linens, towels or clothes Athletes, soldiers, ship crews
127. Trichophyton species The word "trichophyton" literally means "hair plant". Presence of macroconidia in cultures varies and may not help in identification of cultures. Most common species include: Trichophyton mentagrophytes T. rubrum T. tonsurans T. verrucosum T. violaceum T. schoenleinii T. ajelloi (rare infects humans).
128. ON SKIN: Scrapings from skin and nails cannot distinguish species in this genus. ON HAIR: Pattern of infection can help distinguish etiologic or causal agent. For Microsporum species - infections on hair lead to a mosaic pattern of arthrospores. For Trichophyton species - infections on hair follow one of the 4 patterns.
129. Ectothrix - more or less parallel rows of arthrospores produced on surface of hair. 1. Small-spored ectothrix (arthrospores are < 5 mm in diameter) - caused by T. mentagrophytes or T. rubrum (rare). Spores are about the same size as those produced by Aspergillus. 2. Large-spored ectothrix (arthrospores are 5- 10 mm in diameter) - caused by T. verrucosum. Endothrix - growth inside hair shaft only! 3. "Black-dot" endothrix (hair stubs filled with arthrospores) - caused by T. tonsurans or T. violaceum. 4. "Favus hair" endothrix (honeycomb pattern of damage seen on surface of hair shaft) - caused by T. schoenleinii.
130. Trichophyton species Common Features: Colony: Mycelia: Cream, buff to brown, granular to wrinkled Underside: differ (brown to red) Microscopic feature Microconidia; oval- pyriform attached singly, some in clusters have smooth walls Hyaline septate hyphae Areas affected: hair, skin and nails
Skin:Malasseziafurfur and ExophialawerneckiiHair: Trichosporonbeigelii and Piedraiahortae
Pityriasisversicolor/tineaversicolor
Trunk and upper arms (Shoulders & Arms) Damage: purely COSMETIC
Oral treatment: for more advance casesPapule: small circumscribed elevation Pustule: small inflammatory swelling containing pus
Seborrhoea- greasy condition of the scalp, face, sternal region and elsewhere due to overactivity of sebaceous glands (may result to alopecia, acne)genetic predisposition; emotional component
Intravenous infusions of lipid / lipid replacement therapy
Skin scrapings from patients with superficial lesionsblood indwelling catheter tips (fungaemia)
Skin scrapings : 10% KOH, glycerol and Parker ink solution
Superficial infection rarely requires culture, Culture is for systemic infection (blood & intravenous catheter tips)stimulated growht by natural oils or other fatty substances (OLIVE oil)Sabouraud's dextrose agar or Sheep blood agar containing cycloheximide (Acti-Dione) with olive oil INITIAL CLUE TO THIS PATHOGEN IS LACK OF GROWTH IN THE ABSENCE OF OIL
White discoloration of skin (for individuals with brown complexion; light brown discoloration for white/light complexion)
Often misdiagnosed as melanoma
common in Central and South America and South-East Asia (More in tropics and subtropics)epidemics in families: SHARING of combs and hairbrushes
shave or cut the hairs short (Not often acceptable)Sensitive: terbinafine (Dose: 250 mg a day for 6 weeks)
