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LEARNING OBJECTIVES
Upon completion of the chapter, the reader will be able to:
Discuss skin structure and function responsible for preventing infection.
Describe the epidemiology, etiology, pathogenesis, diagnostic criteria, and clinical manifestations associated with acute bacterial skin and skin structure infections (ABSSSIs).
Identify goals of therapy associated with clinical response in patients with ABSSSI.
Recommend effective empiric and definitive antimicrobial regimens when given a diagnosis, patient history, physical examination, and laboratory findings.
Monitor chosen antimicrobial therapy for safety and efficacy.
Apply the Patient Care Process to the management of a patient with ABSSSI.
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Skin and skin structure infections, also known as acute bacterial skin and skin structure infections (ABSSSIs), are frequently encountered in both acute and ambulatory care settings and account for a significant number of outpatient visits and hospitalizations annually.1 ABSSSIs range in severity from mild, superficial, and self-limiting to life-threatening deep tissue infections requiring intensive care, surgical intervention, and intravenous (IV) broad-spectrum antibiotics. Gram-positive pathogens, primarily Staphylococcus aureus and Streptococcus species, are the most common causative bacteria.2-5 Polymicrobial infections are more likely in complicated or deeper infections and in persons with immune suppression, diabetes, vascular insufficiency, or recent surgery.2,5
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The role of methicillin-resistant S. aureus (MRSA), particularly community-acquired MRSA (CA-MRSA), in ABSSSI is of increasing importance. In many US cities, MRSA is the most frequently isolated pathogen from patients presenting to emergency departments with ABSSSI, and antimicrobial prescribing has largely shifted toward empiric use of MRSA-active agents.3 Historically, MRSA infections were associated with healthcare exposure or defined populations such as injection drug users or athletes4,6; however, despite some modest decline in the proportion of S. aureus isolates in recent years, a high MRSA prevalence in the community means that risk stratification may be more difficult to perform. In areas with high rates of CA-MRSA, and in patients with recurrent infections or infections that persist despite appropriate antimicrobial therapy, empiric therapy, including antibiotics active against MRSA, must be considered.2,7 The general management of ABSSSIs is discussed throughout this chapter.
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Intact skin generally is resistant to infection. In addition to providing a mechanical barrier, its relative dryness, slightly acidic pH, colonizing bacteria, frequent desquamation, and production of various antimicrobial defense chemicals, including sweat (which contains IgG and IgA), prevent invasion by various microorganisms.8 Conditions predisposing patients to ABSSSIs include trauma to the skin, alterations in vascularization, and oxygenation leading to decreased skin perfusion, fluid stasis, and altered immune function impairing the body’s ability to fight infection.9
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EPIDEMIOLOGY AND ETIOLOGY
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Impetigo is a common skin infection that can occur in any age-group but most frequently affects children between 2 and 5 years. β-Hemolytic streptococci (Streptococcus pyogenes or Group A Streptococcus [GAS]) and S. aureus are ...