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.

 Direct inf. of skin or subcut. tissue: Impetigo, ecthyma, cellulitis, vulvovaginitis, perianal inf., strepto. ulcers, blistering distal dactylitis, necrotizing fasciitis.  2 ry 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 especially guttate forms.

 Mechanical disruption (inflammations, abrasions)  Prolonged use of steroids, topical or systemic  Presence of systemic illnesses (DM, malignancy)  Immunosuppression  Malnutrition  Anaemia

 Acute contagious skin infection caused mostly by staph. Aureus and strept.  Affects children mainly esp. in summer times.

 1- Non-bullous impetigo: ◦ Caused by staph., strept. or both organisms.  2- Bullous impetigo: ◦ Caused by staph aureus.

Staph. aureus or gp A stretp. (GAS) or both “mixed infections”. May arise as 1 ry inf. or as 2 ry 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 (in pediculosis). Any part could be affected except palms & soles.  Complications: Post- streptococcal acute glomerulo-nephritis “AGN” especially in cases due to strepto. pyogenes M. type 49.

Circinate impetigo: with peripheral extension of lesion & healing in the center.

 Crusted impetigo:  on the scalp complicating pediculosis. Occipital & cervical LNs are usually enlarged & tender.

Ecthyma (ulcerative impetigo): adherent crusts, beneath which purulent irregular ulcers occur. Healing occurs after few wks, with scarring.

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

 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.

 Treatment of predisposing causes: e.g. pediculosis & scabies.  Remove the crusts: by hydrogen peroxide.  Topical antibiotic: e.g. tetracycline, bacitracin, gentamycin, mupiracin (Bactroban ® ), Fusidic acid (Fucidin ® ).

Systemic antibiotics are indicated especially in the presence of fever or lymphadenopathy, in extensive infections involving scalp, ears, eyelids or if a nephritogenic strain is suspected, e.g. penicillin, erythromycin & cloxacillin. Azithromycin (Zithromax ® ) 2 caps 500 mg daily for 3 days in adults. In erythromycin-resistant S. aureus: amoxicillin + clavulanic a. (Augmentin ® ) 25 mg/kg/day.

 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. DD: pseudofolliculitis of the beard, T. barae.

Pseudofolliculitis

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

It is a staphylococcal infection similar to, 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.

 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 cut. cellulitis.

 Erythema, heat, swelling and pain or tenderness.  Fever and malaise which is more severe in erysipelas.  In erysipelas: blistering and hemorrhage.  Lymphangitis and lymphadenopathy are frequent.

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

Recurrences may lead to lymphedema. Subcutaneous abscess. Septicemia. Nephritis.

Systemic antibiotics, especially penicillin, e.g. benzyl penicillin mg IV/6 hrs or cephalosporines. Rest, analgesics.

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.

Topical treatment with azole antifungal agents for 2 weeks or topical fucidin. Erythromycin orally.

A mother brings 5 yr old Johnny to surgery. He has developed this rash, which is weeping and crusting.

 What is the diagnosis?

 A highly infectious skin disease, which commonly occurs in children.

 What is the likely causative organism?

 The causative organism is usually Staphylococcus Aureus or can be strep pyogenes.

 What is the treatment?

Treatment:  Mild localised cases - use topical antibiotic Polyfax  Widespread or more severe infections – use systemic antibiotics, such as flucloxacillin (or erythromycin if penicillin allergic)

A: He does not have to be excluded from school so long as he is on antibiotics B: He has to remain off of school for 5 days from the onset of the lesions C: He must remain off of school until the lesions have crusted or healed D: He must remain off of school until he has completed the antibiotic course.

A 27 year old business man attends surgery complaining of pain and itching in the beard area. You examine him and see the following:

What is the Diagnosis?

 Inflammation of the hair follicle.  Presents as itchy or tender papules and pustules at the follicular openings.  Complications include abscess formation and cavernous sinus thrombosis if upper lip, nose or eye affected.

What is the causative organism?

 Most common cause is Staph Aureus.  Other organisms to consider include:  Gram negative bacteria – usually in patients with acne who are on broad spec antibiotics  Pseudomonas (“Hot tub folliculitis”)  Yeasts (candida and pityrosporum)

What is the treatment?

 Topical antiseptics such as Chlorhexidine  Topical antibiotics, such as Fusidic acid or Mupirocin  More resistant cases may need oral antibioics such as Flucloxacillin  Hot tub folliculitis – ciprofloxacin 2  Gram negative – trimethoprim

 What is the most common causative organsism?

 Streptococcus – Group A Strep Pyogenes.  Others include Group B, C, D strep, Staphylococcus Aureus, haemophilus influenzae (children) and anaerobic bacteria (e.g Pasteurella spp. After animal bites)

 Oral Flucloxacillin or erythromycin if allergic  Co-amoxiclav in facial cellulitis  If severe systemic upset, may require admission for IV antibiotics.  After the acute attack has settled, especially in recurrent episodes – consider the underlying cause

Painful red nodule

 Deeper Staphylococcal abscess of the hair follicle  Coalescence of boils leads to the formation of a carbuncle  Treatment is with systemic antibiotics and may need incision and drainage.  Consider looking for underlying causes, such as diabetes

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