BACTERIAL INFECTIONS OF THE SKIN DR. HADAF A. HASAN

Normal skin flora Millions of micro-organisms mostly in hairy moist areas rich in sebaceous glands. Staph.epidermidis+aerobic diphtheroids predominate on the surface. Anaerobic diphtheroids deep in hair follicles. Stable for each person, usually defensive.

Staphylococcal skin infections IMPETIGO Acute superficial bact. Infection, 2 types: Bullous( mostly by staph.aureus). Non-bullous (mostly by strept. Pyogenes). Either primary or secondary to other skin diseases( scabies, pediculosis…etc.) Mostly in young children, especially late summer.

Non- bullous impetigo Start as thin walled vesicles, rupturing rapidly forming a golden crust on erythematous base. Young children especially face & limbs. Starts as a single lesion & soon becoming multiple, due to auto-inoculation. Transmission is by direct contact.

Bullous impetigo Mostly in neonates & infants. Bullae are due to staphylococcal epidermolytic toxin. Large bullae develop, first clear then cloudy. Finally rupture forming crusts. Occur anywhere especially on the trunk.

ECTHYMA Similar to impetigo, but chronic Ulcer under a crusted surface. Usually at sites of minor neglected trauma. Unlike impetigo, healing is by scarring. Mostly in adults, especially on lower limbs. A sign of neglect & poor hygiene.

Management of impetigo Complications: lymphangitis, adenitis, ssss, &in strept.cases acute glomerulonephritis. Diagnosis is usually clinical. Treatment: if mild only antiseptic solution, with topical antibiotics. If severe or nephritogenic strain of strept. Then a systemic antibiotic is added.

Folliculitis, furuncles & carbuncles Superficial folliculitis involving the ostium of hair follicles. Extremely common, caused by staph. aureus. Can be traumatic after hair depilation, or chemical by mineral oils. Present as pustules healing spontaneously. Mostly children on scalp & limbs.

FURUNCLES ( BOILS) Acute, deep, pustular, infection of hair follicles Starts as a red, tender nodule, enlarges to become pustular, & fluctuant. Finally ruptures discharging pus, healing by scarring, single attack or recurrent. There may be constitutional symptoms. Mostly adolescent boys especially on neck, buttocks & ano-genital area.

A CARBUNCLE A collection of boils due to infection of adjacent hair follicles. Swollen, painful, suppurating area discharging pus from several points. Middle-aged men, esp. with diabetes. V. tender+ severe constitutional symptoms. Mostly on shoulders, neck & hips.

Management of recurrent boils Correction of underlying causes. Swabs for culture from lesions & carrier sites. Topical & systemic antibiotics. Incision of boils & carbuncle to speed healing. Recurrent boils need treatment of carrier states by b.d. topical antibiotics for 6 weeks+ improve patient’s hygiene.

Streptococcal skin infections Erysipelas Acute infection of the skin by group A β hemolytic streptococci. Starts with severe constitutional symptoms. Followed by a rapidly spreading painful red plaque, with well-defined margins, s.t. blisters. Involvement of dermis+ subcutaneous tissue. 80% on the face.

ERYSIPELAS Infecting organism enter through wounds. Prognosis is bad, s.t. fatal. Rapid response to penicillin. Long-term recurrent attacks may occur leading to lymphedema of the affected site. Low dose, long term oral penicillin V can end recurrences.

CELLULITIS Similar to erysipelas, differ by the following: 1) here, a deeper level of infection. 2) in + to srept., other organisms, as staph. aureus , & others can be involved. 3)The lesions are more raised & swollen with less well-defined margins. 4) mostly affecting the lower limbs rather the face.

OTHER COMMON SKIN INFECTIONS ERYTHRASMA Over growth of resident flora corynebacterium minutissimum. Asymptomatic, macular, reddish-brown, well- defined lesions with mild scaling. Affecting body flexures( axillae, groin, toe webs). Coral red fluorescence with Wood’s lamp. Treatment by topical antifungal or antibiotics, s.t. Systemic erythromycins.

ERYSIPELOID A prick from an infected bone, in butchers. Cooks, fishmongers. Erysipelothrix incidiosa is the causative agent. A swollen purple area with clear advancing edge around site of inoculation. Heals spontaneously within few weeks. Rapid response with penicillin.