Clinical meaning
Cutaneous abscesses form when bacteria (most commonly Staphylococcus aureus, including MRSA in community-acquired cases) invade subcutaneous tissue through breaks in the skin barrier. The innate immune system responds with neutrophil recruitment to the site, forming a localized collection of purulent material (dead neutrophils, bacteria, and necrotic tissue). The abscess wall is composed of granulation tissue and a fibrous capsule that limits bacterial spread but also prevents antibiotic penetration, making surgical drainage the definitive treatment. Abscess maturation progresses through cellulitic (diffuse, indurated), fluctuant (liquefied center), and pointing (spontaneous drainage) stages. MRSA prevalence in community-acquired skin and soft tissue infections ranges from 50-70%, influencing empiric antibiotic selection when antibiotics are indicated. Antibiotics alone are insufficient for mature abscesses because poor drug penetration into the walled-off collection fails to achieve bactericidal concentrations.
Diagnosis & workup
Diagnostics & workup: - Perform physical examination: fluctuance, erythema, warmth, tenderness - Order wound culture of purulent drainage (especially if recurrent or immunocompromised) - Consider point-of-care ultrasound to confirm fluid collection and guide drainage - Order CBC, glucose, and inflammatory markers if systemic infection suspected - Assess for surrounding cellulitis requiring antibiotics - Screen for diabetes if recurrent abscesses