Pathogen identification of abscesses and cellulitis.

The goal of culturing abscesses and/or cellulitis is to identify the offending pathogen in order to understand and treat the infection. Abscesses respond to incision and drainage. Antibiotics are not indicated in the patient with normal host defense, and thus in these patients cultures and Gram stains are not indicated. In immunocompromised patients, in patients with abscesses of the central face, and in those with abscesses that contain gas or involve muscle or fascia, Gram stain, culture, and antibiotics are necessary. The Gram stain is a reliable indicator of sterile abscesses, abscesses in pure culture (especially Staphylococcus aureus), and those in mixed anaerobic culture. Location and odor of abscesses are clues to offending bacteria. Cultures of tissue or blood in patients with cellulitis usually are positive in less than 40% of cases, regardless of the technique used. Hemophilus influenzae cellulitis in pediatric patients is an exception; blood cultures are positive in more than two-thirds of cases. Although not specific, certain types of cellulitis show different clinical characteristics. Treatment with elevation, warm soaks, and antibiotics is still the mainstay of therapy. Gram stain and culture are limited to those patients who do not respond to initial therapy or who are immunocompromised.