Antibiotics May Not Be Needed Following Abscess Incision and Drainage

Antibiotics do not improve outcomes after incision and drainage of uncomplicated skin abscesses, but may perhaps prevent new abscesses at one month, according to a new study.

Researchers at Washington Hospital Center (DC, USA) and Wilford Hall Medical Center (Lackland Air Force Base, TX, USAl) conducted a multicenter trial that randomized 212 adults to receive either trimethoprim-sulfamethoxazole (TS, 160 mg/800 mg) or placebo after incision and drainage of community-acquired abscesses. The researchers assessed treatment failure using clinical follow-up, telephone follow-up, and medical record review, recording the development of new lesions within 30 days. All bacterial isolates tested were uniformly sensitive to TS; thus, the primary outcome was treatment failure at 7 days (defined as no improvement after 2 days), development of a new separate abscess within 7 days, or worsening infection within 7 days requiring intervention. In all, 88 patients in the antibiotic group and 102 in the placebo group completed 7 days of follow-up; of these, 46 and 50, respectively, returned at 30 days.

The researchers found that there was no significant difference in treatment failure rates at 7 days (17% in the antibiotic group and 26% in the placebo group). A statistically similar incidence of treatment failure was observed in patients receiving TS compared to placebo. On 30-day follow-up (successful in 69% of the patients), the researchers observed significantly fewer new lesions in the antibiotic (9%) versus the placebo (28%) group. The study was published early online on March 29, 2010, in the Annals of Emergency Medicine.

"Antibiotics don't help with resolution of infection,” said lead author Gillian R. Schmitz., M.D. "The most important thing is to open the wound, clean it, and get the pus out; more study needs to be done to draw a conclusion about recurrence, because we lost so many to follow-up at 30 days.”

Pus consists of a thin, protein-rich fluid, known as liquor puris, and dead cells, which are part of the body's immune response. When neutrophils are needed to fight infection, they move to the site of infection by a process known as chemotaxis, usually triggered by cytokines released from macrophages that sense invading organisms. At the site of infection, the neutrophils engulf and kill bacteria. Eventually, the neutrophils die, and are then phagocytosed by macrophages, which break them down further. Pus is the viscous material composed of these dead neutrophils.

Related Links:
Washington Hospital Center
Wilford Hall Medical Center