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High-Yield Facts

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  • Staphylococcus and Streptococcus are, by far, the most common bacteriological etiologic agents of most superficial skin infections.

  • The marked increase in prevalence of CA-MRSA has made it necessary to consider using an antibiotic that targets this resistant organism (clindamycin or trimethoprim/sulfamethoxazole) when using an oral agent to treat severe, recurrent, or disseminated infections.

  • Poststreptococcal glomerulonephritis is caused by nephritogenic strains of streptococci which can cause skin infections and pharyngitis. It presents a couple of weeks after the primary infection.

  • Tinea corporis can be treated effectively with topical antifungals, but tinea capitis requires long courses (4–8 weeks) of systemic antifungal therapy.

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Impetigo

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Etiology
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Impetigo is a common childhood superficial skin infection seen in preschool and school-aged children that is classically caused by Staphylococcus aureus bacteria but can also be caused by Group A Streptococcus species (Streptococcus pyogenes) which usually peaks in incidence during the summer and fall seasons.1 Given the steady increase in the prevalence of Community Acquired Methicillin Resistant S. aureus (CA-MRSA) over the past two decades, including reports of 40% to 70% prevalence in some areas, antibiotic selection must take into account this prevailing resistance pattern within the community.24

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Pathophysiology
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Impetigo infections occur when bacteria, that is usually present on the surface of the skin, enters into the epidermal layer through areas of skin breaks or microabrasions or at sites of skin trauma. The bacteria then replicates beneath the skin causing the characteristic crusted “honey colored” gold lesions. Transmission of infection occurs through direct contact or fomites.1

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Recognition
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The classic impetigo rash begins with erythematous macular or papular lesions that then progress to superficial vesicles or bullae which then rupture leaving crusted “honey colored” gold lesions. Lesions can be solitary, arranged in clusters, or confluent. Typical distribution include the face, extremities, and/or distal fingers or toes for nonbullous impetigo and intertriginous areas of the neck, diaper area, or axillae for bullous impetigo.1,4

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Management
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Reports indicate that in 15% to 50% of cases, impetigo is a benign self-limited disease lasting 2 to 3 weeks. However, it is easily transmitted to others and some studies report a 5% chance of Group A Strep impetigo leading to acute glomerulonephritis.1,4 Maintaining good skin hygiene, using antibacterial soaps, and/or dilute bleach baths have shown varying degrees of success in eradicating colonization. Over-the-counter topical agents such as bacitracin or neomycin tend to be ineffective due to the emergence of MRSA. Mupirocin or fusidic acid (not approved in the United States) ointments have been the mainstay of topical treatment for impetigo and, in a recent Cochrane review, has evidence of being the most effective treatment.5 Due to reported resistance to mupirocin, a newer agent that has shown promise for the treatment ...

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