Archive for June 28th, 2011

posted by admin on Jun 28

EpidemiologyImpetigo is a common superficial skin infection that is usually caused by S. aureus, but it can also be caused by group A beta-hemolytic streptococci or a combination of the two. Bullous impetigo is usually caused by a toxigenic staphylococcus strain that causes epidermal cleavage. Impetigo is more commonly seen in children, especially those between 2 and 5 years of age. The rash usually occurs on intact skin, but streptococci require traumatized skin to cause infection. Two to 5% of impetigo cases are complicated by post-streptococcal glomerulonephritis, but clusters with rates as high as 15% have been reported.
Signs and SymptomsImpetigo typically occurs around the nose and mouth or on the limbs. It begins as a vesicle (<5 mm) or cloudy pustule that spontaneously ruptures to expose a well-demarcated, red, weeping, shallow erosion. In bullous impetigo, vesicles progress to form bullae (>5 mm) before eroding. A characteristic honey-colored crust accumulates on the lesions. The infections spread both radially and by autoinoculation to form satellite lesions. Lesions are typically asymptomatic, but some patients may report mild pruritis. Regional adenopathy is common, but systemic symptoms are unusual. Without treatment, lesions can persist for months.
DiagnosisThe diagnosis is based on clinical assessment. In recurrent or resistant cases, Gram stain and culture of the lesions should be performed. The differential diagnosis of impetigo includes varicella (chickenpox), herpes simplex virus, candidiasis, atopic or contact dermatitis, scabies, and guttate psoriasis. Impetigo can also arise secondarily from these lesions.
TreatmentTreatment should provide coverage for both S. aureus and streptococci. Topical treatment with mupirocin 2% ointment/cream (Bactroban) works well for isolated lesions. It should be applied three times daily for 7 to 14 days or until the infection is clear. Oral antibiotics are favored by many experts, especially when impetigo is extensive. Options for systemic treatment include cloxacillin, dicloxacillin, clindamycin, amoxicillin-clavulonate, azithromycin, clarithromycin, first- and second-generation cephalosporins, and second-generation fluoroquinolones. Patients should be warned to use contact precautions until lesions begin to heal.
Recurrent ImpetigoRecurrent impetigo has been linked to carriage of S. aureus, especially in the nares. Mupirocin ointment applied to the nares twice daily for 5 days can reduce nasal carriage and infection. The 5-day treatment can be repeated monthly in difficult cases.
Ecthyma (Ulcerative Impetigo)Ecthyma can be considered an ulcerative variation of impetigo. It is caused by streptococci and begins as vesicles or bullae, typically on the legs. These lesions progress to a deeper erosion and have a thick crust that is sometimes gray. Ecthyma arises in minor wounds that are neglected. It should be treated with systemic antibiotics to minimize scarring.*110/348/5*