Bacterial Skin Infections PDF

Bacterial Skin Infections Prof. Ibrahim Al-Adham Taken from Handbook of Nonprescription Drugs 1  Introduction Bacterial skin infection may occur secondary to a contaminated wound or may present as a primary pyodermic infection....

Bacterial Skin Infections Prof. Ibrahim Al-Adham Taken from Handbook of Nonprescription Drugs 1  Introduction Bacterial skin infection may occur secondary to a contaminated wound or may present as a primary pyodermic infection. Pyoderma is a broad term that refers to cutaneous bacterial infection characterized by crusted, oozing lesions with variable amounts of purulence and tenderness. Cultures of primary cutaneous lesions most often reveal S. aureus and Group A streptococci. Gram- negative P. aeruginosa may be present in secondary pyodermas, which are especially prevalent on warm, moist skin such as axillae, ear canals, and interdigital spaces. 2 Introduction- cont Normally, the stratum corneum has only about 10% water content, which is enough to ensure elasticity but is generally below that needed to support luxuriant microbial growth. However, an increase in moisture content may allow microbial growth, leading to infection. A break in the intact skin surface has a deleterious effect on the skin's defensive properties, allowing large numbers of pathogenic organisms to be introduced into the inner layers. In addition, the risk of infection may be increased by excessive scrubbing and irritation of the skin (especially with strong detergents), excessive exposure to water, prolonged occlusion, excessively elevated skin temperature, or local injury. 3  Types of Bacterial Skin Infections The main pyodermic infections are: Impetigo, Ecthyma (ulcerative impetigo), Erysipeloid, Folliculitis, Furuncles and carbuncles, Erythrasma. 4  Impetigo (Primary) Impetigo is a very superficial infection of the skin caused by either S. aureus, Group A P-hemolytic streptococci, or a mixed infection. Impetigo is most common in preschool children and young adults. Direct contact with the infected exudate may result in transmission of the organisms. Predisposing factors include crowded living conditions, poor hygiene, and neglected minor trauma. Lesions first appear as small red spots that may evolve into characteristic vesicles filled with amber fluid. Exudate accumulates and forms yellow or brown crusts (scabs) on the skin surface, often surrounded by erythematous skin. Face, arms, legs, and buttocks are common affected areas. 5  Impetigo Facial impetigo on chin Typical honey-crusted plaque on the lip of an adult with impetigo 6  Ecthyma (ulcerative impetigo) Ecythma refers to an ulcerative bacterial infection caused most frequently by Group A streptococci or staphylococci or both. Children, adolescents, and elderly patients are commonly affected. Ecythma is a lesion of neglect, which develops in excoriations, insect bites, minor trauma in elderly patients, soldiers, sewage workers, alcoholics, and homeless people. These lesions extend much deeper into the dermis than those in impetigo. They have a scattered, discrete arrangement and are commonly distributed on ankles, dorsa of feet, thighs, and buttocks. Lesions are pruritic and tender; they last for weeks and often heal with a scar. 7  Ecthyma (ulcerated impetigo) Impetigo on the face and hand of a homeless Widespread impetigo with honey- man. Note the ecthyma (ulcerated impetigo) crusted erythematous lesions on the on the dorsum of the hand back of a 7-year-old child 8  Erysipeloid Erysipeloid ("crab dermatitis") is an acute but slowly evolving cellulitis occurring at sites of inoculation, most commonly the hands. Often occupational, it is associated with handling fish, shellfish, meat, poultry, hides, and bones. Infection follows an abrasion, scratch, or puncture wound that occurs while organic material containing Erysipelothrix rhusiopathiae, a gram-positive rod, is being handled. The incubation period is 1 to 4 days. The highest incidence occurs in adult men during summer and early fall. Erysipeloid has a characteristic, violaceous, sharply marginated lesion composed of macules and plaques. The lesion is slightly tender and warm but not hot. Skin symptoms include itching, burning, throbbing, and pain. Occasional lymphangitis or Iymphadenitis may occur. Erysipeloid is usually self-limited, subsiding in about 3 weeks. 9 Erysipeloid 10 Folliculitis Folliculitis is a superficial, often bacterial inflammation of hair follicles that heals without scarring. Skin areas regularly exposed to tar, grease, mineral oil, adhesive plaster, and plastic occlusive dressings are most susceptible to folliculitis. S. aureus folliculitis is aggravated by shaving (e.g., beard area, axillae, legs). Skin lesions commonly last for days. 11  Folliculitis Bacterial folliculitis on the back with scarring Close-up of bacterial folliculitis showing hairs and hyperpigmentation coming through pustules 12 Folliculitis Pseudo-folliculitis barbae in a black man. Shaving makes it worse and he notes many problems with ingrown hairs 13  Furuncles and Carbuncles A furuncle is an acute, deep-seated, tender, erythematous, inflammatory nodule that evolves from a staphylococcal folliculitis. A carbuncle is a conglomerate of multiple coalescing furuncles. Children, adolescents, and young adults are frequently affected, and an increased incidence is seen in boys. Chronic cases should be referred to a physician for evaluation of a possible underlying disease. These lesions commonly last for days, with associated skin symptoms of throbbing pain and, invariably, exquisite tenderness. Some patients are subject to recurrent furunculosis. 14  Erythrasma Erythrasma is a chronic bacterial infection that is caused by Corynebacterium minutissimum and affects the intertriginous areas of the toes, groin, and axillae. Adults are generally affected, with a higher incidence in obese middle-aged blacks. Predisposing factors include diabetes and a warm, humid climate. The skin lesions are sharply marginated, brownish red, scaly eruptions that may last for months to years. Irritation may be the only skin symptom. 15  Erythrasma Coral red fluorescence seen with a Wood lamp Erythrasma in the axilla held in the axilla of a patient with erythrasma 16  Treatment of Bacterial Skin infections For the treatment of primary impetigo, a systemic or topical prescription antibiotic is indicated. Topical nonprescription antibiotic preparations with neomycin, bacitracin, and polymyxin B sulfate seem to be most effective when lesions are superficial and are not extensive. Cleaning the area with mild soap and water and gently removing loose crusts should improve response to topical therapy. Because streptococcal infection can occur in other tissues (e.g., renal, heart valve) concurrent with impetigo, most physicians treat impetigo infections with systemic as well as topical products. 17  Treatment of Bacterial Skin infections – cont For the treatment of ecthyma, folliculitis, and erysipeloid, a systemic antibiotic is usually indicated. The role of topical nonprescription antibiotics in these infections is very limited. Furuncles and carbuncles may be resolved with incision, drainage, and the prescription of systemic antibiotics by a physician. Minor cases of erythrasma may respond to showers with povidone iodine soap. However, in most cases, systemic or topical prescription antibiotics are preferred. 18