| Common Bacterial Skin Infections
Normal, healthy skin in patients with an intact and competent immune response is highly resistant to the many microorganisms to which it gets exposed. The hardened, keratinized layer of the epidermis – the stratum corneum – provides a formidable barrier to many bacteria. It is through the breakage or disruption of the integument that bacteria are able to invade and produce the characteristic lesions on the skin and their complications. Disturbance of the skin barrier may be brought about by acts as simple as scratching or rubbing, or by insect bites and foreign bodies (e.g., splinters).
The most frequent bacteria found in common skin infections are Staphylococcus aureus and Streptococcus pyogenes. Together, these two account for majority of the bacterial skin lesions seen in outpatient dermatologic practice. This article presents the typical lesions associated with these infections.
Impetigo is caused by staphylococci, streptococci, or a combination of both. It is contagious and is observed to be more common in children who come in close physical contact. In both types of impetigo, the areas around the nose and mouth, as well as other orifices (e.g., perianal area), are most usually affected. There is consensus that offending staphylococci may be harbored in the nares (inside the nose) before they invade the skin. Impetigo may or may not present with blisters. Known in the vernacular as mamaso (from paso, meaning, scald or burn), the lesions in their early stage look like burns from cigarette stubs. Later on however, the more typical presentation appears, when the roof of the blister collapses, causing a thin, honey-colored crust to appear in the center. In brown- or black-skinned patients, healing is accompanied by darkening of the injured area. When left untreated, impetigo secondary to streptococcal infection may lead to kidney involvement.
Staphylococcus aureus also gives rise to other skin lesions. The term folliculitis refers to inflammation of the hair follicle caused by infection, inflammation and irritation, or physical injury. Staphylococcal folliculitis is perhaps the most common form of infectious folliculitis. On any body surface, a pustule or a group of pustules may appear. This occurs following injury, abrasion, steroid use or even occlusive wound dressings. Another manifestation of staphylococcal infection is sycosis barbae, a deep involvement of the hair follicle. The beard area is affected and becomes studded with large, inflamed pustules. Shaving is identified as the primary culprit, and lesions continue and become more diffuse as shaving is continued on a regular basis. The condition may also be caused by dermatophytic fungi.
Very common during the hot, summer months are furuncles or abscesses (called boils, or pigsa in the vernacular). This is a walled-off collection of pus, forming a reddened, inflamed, softly fluctuant and exquisitely painful mass. S. aureus is the often the culprit, but other bacteria such as E. coli or Pseudomonas may cause these. Furuncles can appear in normal individuals, or may present as part of a syndrome of defective immune states.
Cellulitis and erysipelas are skin infections of the dermis and the subcutaneous tissue that are characterized by redness, swelling and pain. While both staphylococci and streptococci may be responsible, a number of other bacteria play a role as well (e.g., Hemophilus influenzae type B in children less than 3 years of age). Patients present with fever and increased white blood cell count.
Understanding the basic principles leading to bacterial infections is useful in preventing these conditions. Good personal hygiene, especially in warm, humid weather is essential in decreasing colony counts of bacteria. Well-fitting clothes that preclude occlusion in the groin or buttocks are better than tight, ill-fitting ones. Whenever possible, one should avoid scratching, rubbing or manipulating the skin, as this destroys its integrity and compromises its defense. While boils may benefit from incision and drainage, patients are not advised to do this on their own. Non-aseptic techniques and dirty home instruments only serve to propagate the infection.
Management of skin infections entails use of antibiotics, which may be topical or oral. The elimination of the carrier state (as in the nares, in the case of Staphylococcus aureus) may greatly improve outcomes and prevent recurrences. Self-medication with antibiotics is discouraged, because of issues of efficacy, bacterial resistance and unnecessary expense. Early diagnosis and proper treatment, done by medical specialists, markedly decreases the risk of complications and recurrences.
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Dr. Tec Sanchez-Tolosa is a fellow of the Philippine Dermatological Society. Founded in 1952, the PDS is the only recognized affiliate society of the Philippine Medical Association and the Philippine College of Physicians. The Society is committed to maintaining the highest ethical standards in the practice of dermatology through its mission-vision: to be a highly recognized society, locally and globally, striving toward excellence in the attainment of healthy skin for all, through humane service, information dissemination, training and research.
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