A 2-year-old girl in Ethiopia is brought to see the visiting American doctor for a painful swollen hand. The hand was massively swollen and the child did not want to use it. On examination she had a temperature of 99º F and there was visible pus under the skin (Figure 104-1). An incision and drainage was performed and much pus and blood squirted from the abscess. The abscess was packed lightly to stop any bleeding and to prevent it from closing prematurely. Oral antibiotics were given to cover the surrounding cellulitis and any deeper infections. A culture to look for methicillin-resistant Staphylococcus aureus (MRSA) was not available in rural Ethiopia, but close follow-up was set for the next day and the patient was doing much better. The medical team performed twice daily home visits and administered the oral trimethoprim-sulfamethoxazole while changing the dressings. Within one week, the child was playing happily, the erythema and swelling were resolving, and she was beginning to use her hand again.

An abscess is a collection of pus in the infected tissues. The abscess represents a walled-off infection in which there is a pocket of purulence. In abscesses of the skin the offending organism is almost always S. aureus.

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  MRSA was the most common identifiable cause of skin and soft-tissue infections among patients presenting to emergency departments in 11 US cities. S. aureus was isolated from 76 percent of these infections and 59 percent were community-acquired MRSA (CA-MRSA).¹

  
  
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  Risk factors for MRSA infection and other abscesses—Intravenous drug abuse, homelessness, dental disease, contact sports, incarceration, and high prevalence in the community.

  
  
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  In one review of serious skin infections in children admitted to a hospital in New Zealand, the most common types of infection were cellulitis (38%) and subcutaneous abscesses (36%).² The most frequent sites of infection were the head, face and neck (32%), and lower limbs (32%). The most frequently isolated organisms were Staphylococcus aureus (48%) and Streptococcus pyogenes (20%).²

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  Most cutaneous abscesses are caused by S. aureus.

  
  
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  Risk factors for developing an abscess with MRSA include patients who work or are exposed to a health-care system, intravenous drug use, previous MRSA infection and colonization, recent hospitalization, being homeless, African American, and having used antibiotics within the last 6 months.³

  
  
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  Risk factors for hospitalization for staphylococcal skin infections in children in California were age less than 3 years, being Black, and lacking private insurance.⁴

  
  
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  CA-MRSA has become prevalent in the US. One study that evaluated management of skin abscesses drained in the emergency department showed that there was no significant association between amount of surrounding cellulitis or abscess size with the likelihood of MRSA-positive cultures.³

Clinical Features

Collection of pus in or below the skin. Patients often feel pain and have tenderness at the involved site. There is swelling, erythema, warmth, and fluctuance in most cases (Figures 104-1 to 104-3). Determine if the patient is febrile and if there is surrounding cellulitis.