Bacterial Diseases of the Skin

Abstract

When considering common bacterial diseases of the skin, rather distinct clinical responses to a variety of bacterial infections have been identified. In these cases, it is the specific site of infection and the attendant inflammatory responses that provide the characteristic clinical picture. When the pyoderma extends just below the stratum corneum, it is called impetigo. Nonbullous impetigo is the most common pediatric skin infection. It usually starts in a traumatized area. The typical lesion begins as an erythematous papule, after which it becomes a unilocular vesicle. When the subcorneal vesicle becomes pustular, it ruptures and eventually becomes a yellow, golden crust that is a hallmark of the disease process. Bullous impetigo is a less common form of impetigo, accounting for fewer than 30% of all impetigo cases. It occurs in infants and is characterized by rapid progression of vesicles to the formation of bullae measuring larger than 5 mm in diameter in previously untraumatized skin. Treatment of nonbullous impetigo must include intervention against the pathogen as well as improvements in the hygiene and living conditions of the patient. A fundamental tenet is to debride the crust (scab) from the wound surface using poloxamer 188. If the lesions are not widespread, topical mupirocin is the treatment of choice. Treatment of bullous impetigo is similar, except that the local cleansing and topical antibiotic must be complemented by systemic antibiotics if there is evidence of disseminating infections. Ecthyma is usually a consequence of failure to treat effectively impetigo. The untreated infection extends deep into the tissue in shallow ulcerations that often heal without scar. Treatment for ecthyma usually requires systemic antibiotics against either staphylococcus or streptococcus. Folliculitis is a pyoderma located within a hair follicle, secondary to follicular occlusion by keratin, overhydration, or either bacterial or fungal infection. Folliculitis may be divided into either a deep or a superficial type. In the superficial type, the pustule is located at the opening of the hair follicle. In the deep form, the infection may extend beyond the confines of the hair follicle, becoming a furuncle or boil. Carbuncles are aggregates of interconnected furuncles that drain through multiple openings of the skin. Treatment of folliculitis must include searching for and avoiding any factors predisposing to infection. If topical antibiotic therapy is ineffective in controlling the infection, surgical drainage of the infected skin abscess will be necessary. Paronychia is the most common bacterial infection of the hand, which often requires surgical incisional drainage. Similarly, a felon that is an infection of the distal pulp of a finger usually requires surgical drainage. Finally, cellulitis is an acute inflammatory reaction involving the skin and underlying subcutaneous tissue. It usually starts as erysipelas and may advance to lymphangitis, lymphadenitis, or gangrene,which will respond to life-saving interventions in the hospital that usually include systemic antibiotic treatment as well as surgical intervention.