Skin infections: Erythematous plaques:(Fungal etiology): 1-Dermatophytosis: (Tinea): -Diffused Fungal infections of the Keratinized tissues of the body;
Skin infections: Erythematous plaques:(Fungal etiology):
1-Dermatophytosis: (Tinea): -Diffused Fungal infections of the
Keratinized tissues of the body; Stratum corneum, Skin epidermis,
and dermis. -Contagious infection: Direct contact from animals
(goats, sheep, camel, cows, horses) to man (Zoophilic). Transfer
form one area of the body to another Familial cross infection
occurs.
Slide 2
N Clinical presentation of Tinea lesions: -Erythematous
Macules, papular lesions; solid raised skin lesions with defined
borders (less than 1 cm). -Slowly expanded or enlarged patches in
circular erythematous margins; Erythematous plaques where hair has
broken off. -Example: Tinea capitis.
Slide 3
n Classification of Tinea according to infected bodys parts:
1-Tinea capitis: Scalp skin and hair. 2-Tinea corporis: Trunk skin
and hair and other sites. 3-Tinea cruris: Groin area. 4-Tinea
pedis: Foot skin and toenails( Athletes foot). 5-Tinea unguium:
Brown discoloration at the edge of the nails, thick-soft- irregular
nail. Tinea Corporis; Dermatophytosis of skin.
Slide 4
n Mode of transmission of Dermatophytes: -Human to human
-direct skin-to-skin contact with an infected person -Geophilic
species -Keratin - utilizing soil saprophytes -Object to human:
Anthropophilic species; -clothing, bed linens, combs or brushes.
-Animal to human : Zoophilic species: -dogs and cats, especially
kittens -cows, goats, pigs and horses
Slide 5
Diagnosis of dermatophytosis: 1-Clinically: -Clinical
presentation of lesions: itching expanded in a circular
erythematous pattern with skin de- Keratinization. -Woods Lamp:
Blue-green or others. 2-Laboratory: Clinical specimens: Hair, nail,
and skin from lesions margins. Microscopy: 1- A 20% potassium
hydroxide (KOH) wet-mount preparation. -Skin de-keratinization. 2-
A Lactophenol-cotton blue stained preparation. -Fungal stain.
Slide 6
n Causative agents of dermatophytosis: A group of related
filamentous fungi with septate hyphae and Macro- and/or
Microconidia. 1-Microsporum canis: spindle-shaped Macroconidia.
2-Epidermophyton mentagrophytes. 3-Trichophyton mentagrophytes:
-Macro and Microconidia.
Slide 7
n Cultivation of Dermatophytes: - Sabouraud`s dextrose agar
(SDA): the standard media for most fungi. Chloramphenicol added to
inhibit bacterial growth. Microspora canis Trichophytone
mentagrophyte Trichophytone rubrum Therapy: -Itraconazole, or
fluconazole to treat Tinea unguium. -Terbinafine for treatment of
Tinea capitis, Tinea corporis, Tinea cruris, Tinea pedis.
Slide 8
n Erythematous plaques:(Fungal etiology): 2-Candidiasis: (Skin,
Genital area, Mouth). -Causative agent: Usually Candida albicans
(dimorphic). -Oral candidiasis (Thrush): -In Immuno-compromised
patients: Infants, Elderly, AIDS, Others with defect in immunity
-Vaginal candidiasis: -Itching in the genital area. -White, clumpy
discharge. -Transfer of infection to sexual partner. -Seen after
antibiotic therapy.
Slide 9
n Candidiasis: Oval yeast cells of Candida Germ tube positive
test for C.albicans
Slide 10
Subcutaneous Fungal Infection: A-Sporotrichosis: -Caused by
Sporothrix schenkii. -Dimorphic fungi: Cigar-shaped conidia at 25C.
B-Mycetoma (Madura foot): -Localized skin abscess due to
granulomatous infection of dermis and subcutaneous tissue. -Caused
by: 1-Pathogenic soil fungi: Madurella mycetomatis. 2-Bacteria:
Actinomycetoma: Actinomyces species or Nocardia.
Slide 11
N Madura foot: Clinical presentation and etiology: Actinomyces
species: Grams positive braching bacilli.
Slide 12
N C-Chromoblastomycosis and Mycetoma:
Slide 13
Superficial Mycosis: 1-Pityriasis Versicolor: It is a
superficial chronic infection of stratum corneum. Infection of the
keratinized epithelial cells. Causative agent: Malassezia furfur;
(a lipophilic yeast organism; Normal flora of skin). Clinical
presentation: Hypo- or hyperpignented macules on chest or
back.
Slide 14
n Diagnosis: -Skin scraping -Potassium hydroxide (20% KOH)
-Positive for short hyphae and yeast cells - Spaghetti and
meatballs. -Culture.
Slide 15
n 2-Tinea Nigra: Exophiala werneckii : Infection of Stratum
corneum -Black painless patch (Macule) 3-Black Piedra: Piedraia
hortae Infections of scalp hair. 4-White Piedra Trichosporon
beigelii : Fungal infection of facial, axillary or genital
hair.
Slide 16
n Treatment of Superficial Mycosis: -2% salicylic acid -3%
sulfur ointments -Whitfield's ointment -Ketoconazole -Piedra
-Cutting or shaving the hair -Or apply 2% salicylic acid -Or 3%
sulfur ointment -Nizoral shampoo (contains Ketoconazole).
Slide 17
Other skin infections: Necrotic and Ulcerative lesions:
1-Cutaneous Anthrax: Bacillus anthracis infection: -Contaminated
animal products. -Forms about 95% of anthrax cases. -Inoculation of
skin by spores. -Spore germination. -Development of papule.
-Malignant pustule. -Lymph nodes. -Fetal septicemia.
Slide 18
n 2- Primary syphilitic chancre: Treponema pallidum infection.
-Inoculation of microbe into skin cracks. -Development of skin
ulcer(chancre); within three weeks. -The lesion heals
spontaneously, but the microbes spread by blood and lymph.
Slide 19
n 3-Cutaneous Leishmaniasis: -Blood-feeding vector
transmission. -Etiology: Leishmania tropica. (Tissue Mastigophora).
-Sandfly carry the Promastigotes; the infective stage. -Infection
of skin macrophage. -Skin ulceration.
n Viral infection of Skin: Exogenous: -Cutaneous Warts:
-Etiology: Papillomavirus; non-enveloped, DS-DNA virus. -Infection
of skin epidermis (basal cells). -Viral capsid proteins in stratum
corneum. -Cellular proliferation and excess keratin synthesis.
-Thickened dead layer of skin with infectious virus.
