Impetigo, Erysipelas and Cellulitis

Streptococcus pyogenes (group A Streptococcus) is one of the most important Bacterial causes of skin and soft tissue infections (SSTIs) worldwide. In addition, no other pathogen causes as many diverse clinical entities as S. pyogenes. Specifically, this organism causes infections in the superficial keratin layer (impetigo), the superficial epidermis (erysipelas), the subcutaneous tissue (cellulitis), the fascia (necrotizing fasciitis), or muscle (myositis and myonecrosis). It is also the etiologic agent of scarlet fever and Streptococcal Toxic Shock Syndrome (StrepTSS). Impetigo is a non-life-threatening Infection, but can result in post-streptococcal acute glomerulonephritis (AGN). Cellulitis and erysipelas can be mild or moderately severe, while necrotizing fasciitis, myonecrosis and StrepTSS are life-threatening. This chapter focuses on the clinical and epidemiological features of these infections, as well as treatment options, and includes a discussion of Bacterial pathogenesis.