BACTERIAL INFECTIONS OF THE SKIN

Types of Bacterial Skin Infection

BACTERIAL-INFECTIONS-OF-THE-SKIN

1. Impetigo

Erosions covered by honey-colored crusts are diagnostic of impetigo. Staphylococci and group A streptococci are important pathogens in this disease, which histologically consists of superficial invasion of bacteria into the upper epidermis, forming a subcorneal pustule.
Treatment
Impetigo should be treated with an antimicrobial agent effective against Staphylococcus aureus (β-lactamase-resistant penicillins or cephalosporins, clindamycin, amoxicillin–clavulanate) for 7–10 days. Topical mupirocin and fusidic acid (three times daily) are also effective.

2. Bullous Impetigo

All impetigo is bullous, with the blister forming just beneath the stratum corneum, but in bullous impetigo there is, in addition to the usual erosion covered by a honey-colored crust, a border filled with clear fluid. Staphylococci may be isolated from these lesions, and systemic signs of circulating exfoliatin are absent. Bullous varicella is a disorder that represents bullous impetigo as a superinfection in varicella lesions. 
Treatment 
Treatment with oral antistaphylococcal drugs for 7–10 days is effective. Application of cool compresses to debride crusts is a helpful symptomatic measure.

3. Ecthyma

Ecthyma is a firm, dry crust, surrounded by erythema that exudes purulent material. It represents invasion by group A β-hemolytic streptococci through the epidermis to the superficial dermis. This should not be confused with ecthyma gangrenosum. Lesions of ecthyma gangrenosum may be similar in appearance, but they are seen in a severely ill or immunocompromised patient and are due to systemic dissemination of bacteria, usually Pseudomonas aeruginosa, through the bloodstream. 
Treatment 
Treatment is with systemic penicillin.

4. Cellulitis

Cellulitis is characterized by erythematous, hot, tender, ill- defined, edematous plaques accompanied by regional lymphadenopathy. Histologically, this disorder represents invasion of microorganisms into the lower dermis and some-times beyond, with obstruction of local lymphatics. Group A β-hemolytic streptococci and coagulase-positive staphylococci are the most common causes; pneumococci and Hae-mophilus influenzae are rare causes. Staphylococcal infec-tions are usually more localized and more likely to have a purulent center; streptococcal infections spread more rap-idly, but these characteristics cannot be used to specify the infecting agent. An entry site of prior trauma or infection (eg, varicella) is often present. Septicemia is a potential complication. 
Treatment 
Treatment is with an appropriate systemic antibiotic.

5. Folliculitis

A pustule at a follicular opening represents folliculitis. If the pustule occurs at eccrine sweat orifices, it is correctly called poritis. Staphylococci and streptococci are the most frequent pathogens. 
Treatment 
Treatment consists of measures to remove follicular obstruc-tion—either cool, wet compresses for 24 hours or keratolyt-ics such as those used for acne.

6. Abscess

An abscess occurs deep in the skin, at the bottom of a follicle or an apocrine gland, and is diagnosed as an erythematous, firm, acutely tender nodule with ill-defined borders. Staphy lococci are the most common organisms. 
Treatment 
Treatment consists of incision and drainage and systemic antibiotics.

7. Scalded Skin Syndrome

This entity consists of the sudden onset of bright red, acutely painful skin, most obvious periorally, periorbitally, and in the flexural areas of the neck, the axillae, the popliteal and antecubital areas, and the groin. The slightest pressure on the skin results in severe pain and separation of the epidermis, leaving a glistening layer (the stratum granulosum of the epidermis) beneath. The disease is caused by a circulating toxin (exfoliatin) elaborated by phage group II staphylo-cocci. Exfoliatin binds to desmoglein-1 resulting in a separa- tion of cells in the granular layer. The causative staphylococci may be isolated not from the skin but rather from the nasopharynx, an abscess, sinus, blood culture, and so on. 
Treatment 
Treatment is with systemic antistaphylococcal drugs.

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