Management and microbiology of cutaneous abscesses

Cutaneous abscesses in the perineal region contain primarily anaerobes commonly found in stool. Non-perineal abscesses contain mixed microflora indigenous to the skin. Bacteroides fragilis, the only anaerobe resistant to penicillin, is found predominantly in the perineal area. Staphylococcus aureus, although the most common aerobe found, is seen less frequently than expected and is almost always resistant to penicillin. Escherichia coli and Neisseria gonorrhoeae are rarely found. Incision and drainage is the primary mode of treatment. Fever is rare, though tachycardia is common in patients with normal host defenses. Patients with altered host defenses may require initial culture and Gram-stained smear to determine appropriate antibiotic therapy. The Gram-stained smear reliably indicates sterile and mixed abscesses, as well as those containing pure S aureus. Incision and drainage alone is the only therapy required in the usual patient. Since in these patients antibiotics are not required, initial culture and Gram-stained smear are unnecessary.