Bacterial infection of the skin (pyodermas)
Bacterial skin infection is one of the commonly encountered problems in the tropics.
Pyoderma is a cutaneous infection with pyogenic (pus-forming) bacteria. When the normal protective functions of the skin are altered by trauma (scratching and excoriation ), pre existing and/or coexisting skin diseases like, eczema, scabies or venous or lymphatic insufficiency, pathogenic organisms get access to the skin to establish infection.
Although the term pyoderma literally means “pus in the skin,” the pus may not always be visible to the naked eye.
Common skin infections include cellulitis, erysipelas, impetigo, folliculitis, and furuncles and carbuncles.
Eysipelas
Erysipelas is a bacterial infection of the dermis and upper subcutaneous tissue;characterized by a well-defined, raised edge reflecting the more superficial (dermal) involvement
Erysipelas is a bacterial skin infection involving the upper dermis that characteristically extends into the superficial cutaneous lymphatics. It is a tender, intensely erythematous, indurated plaque with a sharply demarcated border. Its well-defined margin can help differentiate it from other skin infections (eg, cellulitis).
Impetigo
Impetigo is a contagious superficial (stratum corneum) pyogenic infection of the skin. Impetigo is a common bacterial skin infection caused by Group A Streptococcus (GAS) or "strep."
Two main clinical forms are recognized: non-bullous impetigo (or impetigo contagiosa) and bullous impetigo. Impetigo presents as either a primary pyodermal of intact skin or a secondary infection due to preexisting skin disease or traumatized skin. Impetigo rarely progresses to systemic infection, although post streptococcal glomerulonephritis may occur as a rare systemic complication. Impetigo occurs in individuals of all ages. However, children younger than 6 years have a higher incidence of impetigo than adults. Bullous impetigo is most common in neonates and infants Causative agents It is caused by Staphylococcus aureus.The non-bullous form is usually caused by group Aβ streptococcus, in some geographical areas Staphylococcus aureus or by both organisms together.
Clinical features
Non-bullous impetigo: The characteristic lesion is a fragile vesicle or pustule that readily ruptures and becomes a honey-yellow, adherent, crusted papule or plaque and with minimal or no surrounding redness and usually occurs on hands and face. unless secondary infection exists (cellulites) Lesions develop on either normal or traumatized skin or are superimposed on a preexisting skin condition (e.g., scabies, varicella, atopic dermatitis). Lesions are located at exposed parts of the body (e.g., scalp, arms, legs), sparing the palms and soles. Localized lymphadenopathy usually is present, and nodes may be tender.
Bullous impetigo:
The characteristic lesion is a vesicle that develops into a superficial flaccid bulla on intact skin, with minimal or no surrounding redness. Initially, the vesicle contains clear fluid that becomes turbid. The roof of the bulla ruptures, often leaving a peripheral collarette of scale if removed; it reveals a moist red base.
Management
Local management for small lesions: - Wash with betadine solution or saline. Potassium permanganate 1 in 1000 solution soaking twice a day until the pus exudates dry up. Gentian violet (GV) paint 0.5% apply BID. Topical antibiotics can be used, such as 2% mupirocin, Gentamycine, Fucidic acid can be usedbut costly.
Systemic treatment: - for impetigo contagiosa, a single dose of benzathin penicillin coupled with local care. Oral amoxacyllin or Ampicillin can also be used. For Bullous impetigo: - cloxacillin 500 mg po QID for 7 to 10 days. In cases, with an allergy to penicillin, erythromycin can be given. The underlining skin conditions such as eczemas, scabies, fungal infection, or pediculosis should be treated. When impetigo is neglected it becomes ecthyma, a superficial infection which involves the upper dermis which may heal forming a scar.
Folliculitis
It is an infection of the hair follicles. It occurs on hair bearing areas of the skin. Application of greasy substance such as Vaseline is a predisposition. The most common etiologic agent is staphylococcus aureus. However, fungi and virus can also cause it. A furuncle is an acute, deep-seated, red, hot, tender nodule or abscess that evolves around the hair follicle and is caused by staphylococcus aureus.
A carbuncle is a deeper infection comprised of interconnecting abscesses usually arising in several adjacent hair follicles.
Furuncle and carbuncle are common in obese, diabetic patients and immunosuppressive conditions.
Management of folliculitis
Avoid greasy applications on the skin. Mupiricine topically can be used. Systemic antibiotics: - cloxacillin or erythromycin is choices of treatment. For deep abscesses (furuncle and carbuncle) incision and drainage is mandatory.