CLINICAL AND LABORATORY INVESTIGATIONS Pediatric Dermatology Vol. 11 No. 4 293-303 Impetigo; An O¥erview Gary L. Darmstadt, M.D., and Alfred T. Lane, M.D. Department of Dermatology, Stanford University School of Medicine, Stanford, California Abstract: This article reviews in detail tiie pathogenesis, ciinical char- acteristics and management of impetigo in children. Impetigo is the most common bacterial skin infection of children. Most cases of nonbullous impetigo and al! cases of bulious impetigo are caused by Stapfiy/ococcus aureus. The remainder of cases of nonbullous impetigo are due to group A beta bemoiytic streptococci (GABHS). GABHS colonize tbe skin directly by binding to sites on fibronectin tbat are exposed by trauma. In contrast, S. aureus colonizes the nasal epithelium first; from this reservoir, coloni- zation of the skin occurs. Patients with recurrent impetigo shouid be eval- uated for carriage of S. aureus. Superficial, localized impetigo may be treated successfully in more than 90% of cases with topicai application of mupirocin ointment. Impetigo that is widespread or involves deeper tis- sues should be treated with a beta-lactamase-resistant oral antibiotic. The choice of antibiotics is affected by the local prevalence of resistance to erythromycin among strains of S. aureus, antibiotic cost and availability, and issues of compliance. Skin complaints or findings are noted in 20% to 30% of children who attend general pediatric clinics (Table 1) (1,2). Bacterial skin infection is the single most common diagnosis among those with skin problems, accounting for 17% of all clinic visits. The most common bacterial skin infection of chil- dren is impetigo, which makes up approximately 10% of all skin problems (1,2). PATHOGENESIS In order to understand the pathogenesis of im- petigo, it is essential to appreciate the factors which alter the normal flora of the skin and which promote colonization and infection of the skin with patho- genic bacteria. This subject has recently been re- viewed extensively by Roth and James (3). Resident and Transient Cutaneous Flora Normal skin microflora falls into two broad catego- ries: 1) resident flora which are attached to the skin and are present in relatively stable numbers, and 2) transient flora, which are introduced from the envi- ronment onto exposed skin and lie free on the skin surface, without attachment in the absence of a dis- turbance in the integrity of the skin (3). The most important of the transient bacteria are the group A beta-hemolytic streptococci {Streptococcus pyo- genes; GABHS) and Staphylococcus aureus. Coagulase-negative staphylococci are the most numerous of the resident flora, whereas coagulase- positive S. aureus encounters a high degree of nat- ural resistance to colonization of the skin. Most body sites are free from colonization with S. aureus (4). However, persistent nasal carriage is detected in 20% to 40% of normal adults (5,6), and up to 20% of people may be colonized on the perineum (7). In contrast, patients with atopic dermatitis will yield S. aureus from upwards of 90% of skin lesions and 70% of cultures from nonlesional skin (8,9). Coryneform organisms are lipophilic, pleomor- Address correspondence to Gary L. Darmstadt, M.D., De- partment of Dermatology, Stanford University School of Medi- cine, 900 Blake Wilbur Drive, Palo Alto, CA 94304. 293