Editor’s note: This month’s KCQ first appeared in July 2009, and since that time it has been one of our website’s most-read articles, generating 23,000-plus pageviews.
A previously healthy 55-year-old white female presents to the ED with a three-day history of pain and erythema in her right hand. Examination reveals fluctuance as well. She is diagnosed with an abscess with surrounding cellulitis. The abscess is incised, drained, and cultured, and she is sent home on oral trimethoprim/sulfamethoxazole. The following day, her cellulitis has worsened. She is hospitalized and commenced on intravenous vancomycin. What is the best empiric therapy for community-acquired cellulitis?
Cellulitis is defined as a skin and soft-tissue infection (SSTI), which develops as a result of bacterial entry via breaches in the skin barrier. Typically, it involves the dermis and subcutaneous tissue and is associated with local tenderness, erythema, swelling and fever. Cellulitis usually affects the lower extremities, but it can affect other locations, resulting in diagnoses such as periorbital, abdominal wall, buccal, and perianal cellulitis.1,2
Gram-positive organisms, especially Staphylococcus aureus and beta hemolytic streptococci, are the most common causes of cellulitis. Although it is less common, cellulitis can be caused by gram-negative organisms. The recent significant increase in the prevalence of SSTIs due to community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has led to changes in the selection of antibiotics that were most commonly utilized to empirically treat cellulitis.
The diagnosis of cellulitis is based primarily on clinical manifestations. Due to low diagnostic yields, blood cultures, needle aspiration, or punch biopsy specimens usually are not helpful in the setting of simple cellulitis.3 Therefore, antibiotic therapy is almost universally started empirically. Starting appropriate initial antibiotic therapy improves patient outcomes by reducing mortality rates, length of stay, and inpatient costs.4
Cellulitis incidence is about two cases per 1,000 patient-years.5 This rather high incidence, coupled with escalating rates of SSTIs due to CA-MRSA, demands reliable and cost-effective treatment strategies for the management of community-acquired cellulitis.
Review of the Data
The treatment of community-acquired cellulitis was straightforward until the past decade, as physicians saw a significant increase in CA-MRSA incidence.6 MRSA was reported initially in 1961, only two years after methicillin was introduced into clinical practice.7,8 Subsequently, MRSA prevalence increased dramatically, and by the beginning of this decade, more than 50% of the Staphylococcus aureus hospital strains were resistant to methicillin.8 Furthermore, 60% to 80% of community-acquired Staphylococcus aureus strains in the U.S. are methicillin-resistant.8
The two major types of MRSA infections are healthcare-acquired (HA-MRSA) and community-acquired (CA-MRSA). The HA-MRSA infection group is further subdivided into those strains that develop during a period of hospitalization and those that develop following contact with healthcare facilities (e.g. hospitalization or surgery within the previous year). This subgroup includes HA-MRSA infections in hemodialysis patients, residents of long-term-care facilities, and individuals who have a vascular catheter or other indwelling device.9,10