Chapter 14: Bacterial Skin Infections

Impetigo represents a highly contagious superficial infection commonly seen in children, presenting in nonbullous forms with characteristic honey-colored crusts typically caused by Staphylococcus aureus or Streptococcus species, and in bullous variants caused exclusively by S. aureus that feature fragile fluid-filled lesions. The chapter details how diagnosis relies primarily on clinical appearance and how management progresses from topical antimicrobials in mild cases to systemic oral antibiotics for widespread or bullous presentations. Folliculitis encompasses superficial-to-deep hair follicle infections most frequently caused by coagulase-negative Staphylococcus or Pseudomonas aeruginosa, presenting as small pustules with surrounding erythema, with treatment emphasizing hygiene measures and antimicrobial therapy tailored to the causative organism. Furuncles and carbuncles represent progressively deeper infections arising from folliculitis, mediated almost exclusively by S. aureus including methicillin-resistant strains, with furuncles developing as localized abscesses from individual follicles and carbuncles forming as multiloculated structures combining multiple furuncles that frequently require incision and drainage alongside systemic antibiotics. The chapter concludes with cellulitis, a serious infection of the dermis and subcutaneous tissues presenting as diffuse, warm, erythematous areas with indistinct borders, and highlights critical variants including erysipelas with sharply demarcated borders, necrotizing fasciitis as a surgical emergency spreading rapidly with disproportionate pain, and periorbital cellulitis threatening cranial structures. Throughout, the chapter emphasizes appropriate empirical antibiotic selection, recognition of severe variants requiring hospitalization and surgical intervention, and prevention of serious complications through appropriate clinical judgment and timely referral.