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Bacterial Infections of the Skin

Furuncles and Carbuncles

A furuncle, or boil, is an acute perifollicular staphylococcal abscess of the skin and subcutaneous tissue. Lesions appear as an indurated, dull, red nodule with a central purulent core, usually beginning around a hair follicle or a sebaceous gland. Furuncles occur most commonly on the nape, face, buttocks, thighs, perineum, breast.

A carbuncle is a coalescence of interconnected furuncles that drain through a number of points.

The most common cause of furuncles and carbuncles is coagulase-positive S aureus. Cultures should be obtained from all suppurative lesions.

Treatment of Furuncles and Carbuncles

Warm compresses and cleansing.

Dicloxacillin (Pathocil) 500 mg PO qid .

Manipulation and surgical incision of skin infections, cellulitis, superficial folliculitis, impetigo early lesions should be avoided, because these maneuvers may cause local or systemic skin infections, cellulitis, superficial folliculitis, impetigo extension. However, when the lesions begin to suppurate and become fluctuant, drainage may skin infections, cellulitis, superficial folliculitis, impetigo.

Draining lesions should be covered with antibiotics

Superficial Folliculitis    Impetigo    Impetigo

Superficial folliculitis is characterized by small dome-shaped pustules at the ostium of hair follicles. It is caused by coagulase-positive S aureus.

Multiple or single lesions appear on the scalp, back, and extremities. In children, the scalp is the most common site.

Gram stain and bacterial culture supports the diagnosis.

Treatment. Local cleansing and erythromycin 2% solution applied topically bid to affected areas.

Impetigo

Impetigo consists of small superficial vesicles, which eventually form pustules and develop a honey-colored crust. A halo of erythema often surrounds the lesions.

Impetigo occurs most commonly on exposed surfaces such as the extremities and face, where minor trauma, insect bites, contact dermatitis, or abrasions may have occurred.

Gram stain of an early lesion or the base of a crust often reveals gram-positive cocci. Bacterial culture yields S aureus, group A beta-hemolytic streptococci, or both.

Treatment of Impetigo

A combination of systemic and topical therapy is recommended for moderate to severe cases of impetigo for a 7- to 10-day course:

Dicloxacillin 250-500 mg PO qid. Dicloxacillin should be the initial treatment because erythromycin-resistant strains of S aureus are prevalent.

Cephalexin (Keflex) 500 mg PO qid.

Erythromycin 250-500 mg PO qid is used in penicillin allergic patients.

Mupirocin (Bactroban): Highly effective against staphylococci and Streptococcus pyogenes. Applied bid-tid for 2-3 weeks or until 1 week after lesions heal. Bacitracin (neomycin, polymyxin B) ointment tid.

Complications

Acute glomerulonephritis is a serious complication of impetigo, with an incidence of 2-5%. It is most commonly seen in children under the age of 6 years old. Treatment of impetigo does not alter the risk of acute glomerulonephritis.

Rheumatic fever has not been reported after impetigo.

Cellulitis

Cellulitis is a diffuse suppurative bacterial inflammation of the subcutaneous tissue. It is characterized by localized erythema, warmth, and tenderness. Cutaneous erythema is poorly demarcated from uninvolved skin. Cellulitis may be accompanied by malaise, fever, and chills.

The most common causes are beta-hemolytic streptococcal and S aureus. Complications include gangrene, metastatic abscesses.

Treatment

Dicloxacillin or cephalexin provide adequate coverage for either streptococci and staphylococci. Penicillin may be added.