BACTERIAL SKIN INFECTION

KUSHAL KUMAR

BACTERIAL INFECTION OF SKINThe SkinDefinition

Skin is largest organ of body. It protects underlying tissues and organs, protects body from mechanical injury, and ultraviolet rays of sun.

SKIN INFECTIONS

• The skin always has some amount of bacteria, fungus and viruses living on it.

• Occur when there are breaks in the skin and the organisms have uncontrolled growth

Staph. Aureus Infection

1. Direct infection of skin : impetigo, ecthyma, folliculitis,

furunculosis, carbuncle, sycosis.

2. Secondary infection: eczema, infestations, ulcers, …etc.

3. Effect of bacterial toxin: staph.-associated scalded skin

syndrome (SSSS), toxic shock syndrome.

Strepto. Infection(gp A streptococci)

Direct inf. of skin or subcut. tissue: Impetigo, ecthyma, cellulitis, vulvovaginitis, perianal inf., ulcers, blistering, necrotizing fasciitis.

2ry inf.: eczema, infestations, ulcers, …etc.

Tissue damage from circulating toxin: scarlet fever, toxic shock-like syndrome.

Skin lesions attributed to allergic hyper-sensitivity to strepto. antigens: erythema nodosum, vasculitis.

Skin dis. provoked or influenced by strepto. inf.: psoriasis

IMPETIGO

•Acute contagious skin infection caused mostly by staph. Aureus and strept.

•Affects children mainly, esp. in summer times.

CLINICAL TYPES

•1- Non-bullous impetigo: • Caused by staph., strept. or both organisms.

•2- Bullous impetigo:• Caused by staph aureus.

NON-BULLOUS IMPETIGO

• Staph. aureus or gp A stretp. or both “mixed infections”.

• May arise as 1ry inf. or as 2ry inf. of pre-existing dermatoses, e.g.

pediculosis, scabies & eczemas.

• An intact st. corneum is probably the most important defense against

invasion of pathogenic bacteria.

• A thin-walled vesicle on

erythematous base, that soon

ruptures & the exuding serum

dries to form yellowish-brown

(honey-color) crusts that dry &

separate leaving erythema

which fades without scarring.

• Regional adenitis with fever

may occur in severe cases.

Sites: Exposed parts eg. face & extremities. Scalp .Any part could be affected except palms & soles.

Complications: Post-streptococcal acute glomerulo-nephritis “AGN” especially in cases due to strepto. pyogenes

VARITIES:

• Circinate impetigo: with

peripheral extension of

lesion & healing in the

center.

•Crusted impetigo: • on the scalp complicating

pediculosis. Occipital & cervical Lymph nodes are usually enlarged & tender.

• Ecthyma (ulcerative

impetigo): adherent crusts,

beneath which purulent

irregular ulcers occur. Healing

occurs after few weeks, with

scarring.

• Site: more on distal extremities (thighs & legs).

BULLOUS IMPETIGO

• Age: all ages, but commoner in childhood & newborn (impetigo neonatorum).

• Site: face is often affected, but the lesions may occur anywhere, including palms & soles.

• The bullae are less rapidly ruptured (persist for 2-3 days) & become much larger. The contents are at first clear, later cloudy. After rupture, thin, brownish crusts are formed.

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BULLOUS IMPETIGO

•

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BULLOUS IMPETIGO

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BULLOUS IMPETIGO

TREATMENT OF IMPETIGO:

Treatment of predisposing causes: e.g. pediculosis & scabies.

Remove the crusts: by olive oil or hydrogen peroxide.

Topical antibiotic: e.g. tetracycline, gentamycin,

FOLLICULITIS

• inflammatory disease of the hair follicles, which may be

infectious or non-infectious.

SUPERFICIAL FOLLICULITIS (BOCKHART’S IMPETIGO)

• a dome-shaped pustule at the orifice of a hair follicle that heals within 7-10 days.

• Caused by staph aureus and affects mainly extremities and scalp.

• Topical steroids are a common predisposing factor.

SYCHOSIS VULGARIS

• Recurrent red follicular papules

or pustules centered on a hair,

usually remain discrete over the

beard or upper lip, but may

coalesce to produce raised

plaques studded with pustules.

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SYCOSIS VULGARIS

PSEUDOFOLLICULITIS

• from penetration into the skin of sharp tips of shaved hairs.

FRUNCULOSIS (BOILS)

• It is a staphylococcal infection , but

deeper than folliculitis & invades

the deep parts of the hair folliculitis.

• Occasionally several closely

grouped boils will combine to form

a carbuncle. The carbuncle usually

occurs in diabetic cases. The site of

election is the back of the neck.

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FURUNCLE

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FURUNCLE / CARBUNCLE

CELLULITIS & ERYSIPELAS

•Cellulitis is an infection of subcutaneous tissues.

• Ersipelas: It’s due to infection of the dermis & upper subcutaneous tissue by gp A streptococci. The organism reaches the dermis through a wound or small abrasion. It is regarded as a superficial “dermal” form of cellulitis.

Erythema, heat, swelling and pain or tenderness.

Fever and malaise which is more severe in erysipelas.

In erysipelas: blistering and hemorrhage.

Lymphadenopathy are frequent.

• Edge of the lesion: well demarcated and raised in erysipelas and diffuse in cellulitis.

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CELLULITIS

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CELLULITIS

COMPLICATIONS

• Recurrences may lead to lymphedema.

• Subcutaneous abscess.

• Septicemia.

• Nephritis.

TREATMENT

• Systemic antibiotics, especially penicillin, e.g. benzyl

penicillin (600-1200 mg IV/6 hrs)

• Rest, analgesics.

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ERYSIPELAS

SKIN DISEASES RELATED TO CORYNEFORM BACTERIA

ERYTHRASMA

• It is mild, chronic, localized

superficial infection of skin by

Coryn. Minutissimum.

• Clinically: sharply-defined but

irregular brown, scaly patches

• usually localized to groins,

axillae, toe clefts or may cover

extensive areas of trunk &

limbs. Obesity & DM may

coexist.

• Coral red fluorescence under

wood’s light.

TREATMENT

• Topical treatment with azole antifungal agents for 2 weeks

or topical fucidin.

• Erythromycin orally.

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