Chapter 90: Soft Tissue Infections

INTRODUCTION

Skin and soft tissue infections are common, and their successful evaluation and management involve an understanding of disease severity. Infection and patient characteristics help guide appropriate antibiotic treatment, outpatient or inpatient options, and potential surgical therapy.

METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of soft tissue infections in adults and children. Understanding treatment guidelines for community-acquired MRSA is important for managing soft tissue infections in the ED.

Clinical Features

Community-acquired MRSA causes skin lesions that are typically warm, red, tender, and commonly associated with soft tissue abscesses that may be spontaneously draining. MRSA lesions are frequently mistaken as spider bites.

Diagnosis and Differential

The diagnosis of MRSA is typically made based on clinical features. Consider the likelihood of community-acquired MRSA for soft tissue infection where S. aureus or Streptococcus are typically considered common etiologic pathogens. This includes skin and soft tissue infections as well as sepsis and pneumonia. Bedside ultrasound may be helpful to identify abscess collections in cases where physical examination is equivocal.

Emergency Department Care and Disposition

1. For many community-acquired MRSA cutaneous infections where abscesses have developed, local incision and drainage is sufficient treatment to successfully manage these infections. Most patients with normal immune system function will not require additional treatment with antibiotics for small abscesses without accompanying cellulitis or systemic signs of severe illness when the lesions can be successfully incised and drained.

2. For patients with immunocompromise, systemic illness, surrounding cellulitis, or other characteristics prompting antibiotic treatment, consider antibiotics effective against MRSA when appropriate. Options include clindamycin 300 mg PO four times daily or trimethoprim/sulfamethoxazole double strength two tablets twice a day for 7 to 10 days. Consider adding cephalexin 500 mg four times daily to cover Streptococcus when using trimethoprim/sulfamethoxazole. For severe infections, vancomycin 1 g IV every 12 hours is recommended along with inpatient admission.

3. Patients at the extremes of age, or those who have systemic signs of severe illness, significant comorbidities, or large complicated lesions may benefit from an admission for parenteral antibiotics and surgical consultation when indicated.

NECROTIZING SOFT TISSUE INFECTIONS

Necrotizing soft tissue infections are aggressive and potentially life threatening infections. These infections can present with an insidious onset and early findings may appear deceptively benign. Necrotizing soft tissue infections represent a spectrum of conditions that may be polymicrobial or monomicrobial. Group A Streptococcus and S. aureus are often the etiologic agents in monomicrobial infections. Clostridial infections are now uncommon secondary to improved hygiene and sanitation.

Clinical Features

Patients present with pain out of proportion to physical findings and a sense of heaviness in the affected part. Physical findings may include a combination of edema, brownish skin discoloration, bullae, malodorous serosanguineous discharge, and crepitus. Patients may have low-grade fever ...