Antibiotics May Not Be Needed After Abscess Incision and Drainage

News Author: Karla Gale, MS
CME Author: Penny Murata, MD
Authors and Disclosures
CME Released: 04/09/2010; Valid for credit through 04/09/2011
April 9, 2010 — Antibiotics don't improve outcomes after incision and drainage of uncomplicated skin abscesses, new research indicates. They might prevent new abscesses at one month, however.
"We're seeing so many abscesses now," lead researcher Dr. Gillian R. Schmitz told Reuters Health. Before methicillin-resistant Staphylococcus aureus (MRSA) became so widespread, most abscess patients had diabetes or were immunocompromised, she said, "but now they're popping up all over the place in people with no traditional risk factors."
"But no one has studied best practice for treating abscesses," Dr. Schmitz added.
In a multicenter trial, she and her colleagues randomized 212 adults to receive trimethoprim-sulfamethoxazole (160 mg/800 mg) or placebo after incision and drainage of community-acquired abscesses. They instructed patients to take 2 pills twice daily for seven days. 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.
Eighty-eight patients in the antibiotic group and 102 in the placebo group completed 7 days of follow-up; 46 and 50, respectively, returned at 30 days.
According to their March 29th online report in the Annals of Emergency Medicine, all bacterial isolates were uniformly sensitive to trimethoprim-sulfamethoxazole. Still, there was no significant difference in treatment failure rates at 7 days (17% in the antibiotic group and 26% in the placebo group, p = 0.12).
"Antibiotics don't help with resolution of infection," Dr. Schmitz said. "The most important thing is to open the wound, clean it, and get the pus out."
However, the total number of new lesions at 30 days was significantly lower in the antibiotic group: 9% vs 28% (p = 0.02).
"More study needs to be done to draw a conclusion about recurrence, because we lost so many to follow-up at 30 days," Dr. Schmitz said.
A separate trial in children with community-acquired skin abscesses found similar results. In a paper scheduled for print publication in the May issue of same journal, Dr. Myto Duong, currently at Southern Illinois University, Springfield, and associates report outcomes in 149 children after incision and drainage. The 73 children randomized to the intervention group took trimethoprim-sulfamethoxazole for 10 days (10-12 mg trimethoprim/kg/day in 2 divided doses, with a maximum of 160 mg per dose, in a liquid formulation containing 200 mg sulfamethoxazole/40 mg trimethoprim per 5 mL). The other 76 children received placebo.
The authors found no significant difference in failure rates at 10 days — 4.1% in the antibiotic group vs 5.3% in the placebo group. In addition, the antibiotic group had a significantly lower incidence of new lesions at day 10 (12.9%, vs 26.4% in the placebo group).
At 30 days, however, with 46 children in the antibiotics group and 52 in the placebo group evaluable, there was no longer a significant difference in the rate of new lesions (28.3% vs 28.8%, respectively).
"Antibiotics are not required for pediatric skin abscess resolution," Dr. Duong's group concludes, adding that further research is needed to see if antibiotics help prevent new lesions in the short term.
Both studies were limited by attrition of patients and by inclusion of subjects who were otherwise healthy, so the results can't be generalized to patients with comorbidities. In Dr. Duong's trial, medication compliance was only 66%.
In an editorial, Dr. David A. Talan of Olive View--UCLA Medical Center in Sylmar, California, states, "Antibiotics for drained simple abscesses are not required to meet the standard of care."
He told Reuters Health, "The rate of resolution of patient groups described in these studies is very high, so doctors can feel that the odds are on their side" if they forego antibiotic treatment, "and they can reassure patients there's a good chance that things will work out fine."
But, he continued, physicians should be aware of the tendency for abscesses to return, and they should advise patients to seek attention if new symptoms appear after first infection resolves.
Ann Emerg Med. Published online March 29, 2010.
Reuters Health Information 2010. © 2010 Reuters Ltd.
Clinical Context
In the November 2007 issue of Antimicrobial Agents and Chemotherapy, Rajendran and colleagues reported that after incision and drainage for abscess, improvement at 7 days occurred in 84% of patients receiving antibiotics and 91% of patients receiving placebo. In children with skin abscesses, rates of treatment failure were similar for those treated with trimethoprim-sulfamethoxazole vs placebo, as found by Duong and colleagues in the May 5, 2009, online issue of the Annals of Emergency Medicine.
This multicenter, double-blind, randomized, placebo-controlled trial evaluates whether treatment with trimethoprim-sulfamethoxazole for uncomplicated skin abscesses reduces treatment failure in the first 7 days and the rate of new lesion formation in the first 30 days after incision and drainage in adults.
Study Highlights
• 212 adults 16 years or older from a convenience sample of 220 adults with uncomplicated skin abscesses requiring incision and drainage were enrolled.
• 4 military emergency departments participated.
• Exclusion criteria were immunocompromised status, pregnancy, breast-feeding, allergy to sulfa drugs, fever or systemic illness, antibiotic use in the prior week, hospitalization in the prior month, abscess on the face, suspected tracts or fistulas, and need for drainage in the operating room.
• Standard practice was used to drain and pack abscesses.
• Incision length, irrigation, and ultrasonography use were dependent on the individual physician.
• Wound cultures were sent for aerobic and anaerobic cultures and antimicrobial susceptibility testing.
• 96 patients were randomly assigned to receive trimethoprim-sulfamethoxazole (160 mg/800 mg) 2 pills twice daily for 7 days.
• 116 patients were randomly assigned to receive placebo.
• The placebo group vs the trimethoprim-sulfamethoxazole group had similar baseline characteristics of age (range, 17 - 79 years), sex, abscess location, cellulitis size, and abscess size.
• The most common abscess location was an extremity (47% - 49%).
• Patients were asked to follow up in the emergency department at 2 days and again at 7 days for wound check.
• Primary outcome measure was treatment failure within 7 days.
• Treatment failure in 7 days was defined as no improvement after 2 days, new separate lesion within 7 days, or worsening infection within 7 days requiring intervention (increased diameter of abscess, cellulitis, fever, or systemic response requiring further antibiotic use, additional incision and drainage, surgical debridement, or hospital admission).
• Secondary outcome measure was formation of new lesions, abscess, or pustule within 30 days.
• 3 sites assessed secondary outcome by telephone calls, return visits to the emergency department, and review of medical records.
• Culture results revealed MRSA in 53% of patients overall: 47 (47%) of 100 patients in the placebo group and 50 (60%) of 84 patients in the trimethoprim-sulfamethoxazole group.
• All MRSA isolates were sensitive to trimethoprim-sulfamethoxazole.
• At 7-day follow-up of 190 (90%) of 212 subjects, the treatment failure rate was statistically similar for the placebo group (27 [26%] of 102 patients) vs the trimethoprim-sulfamethoxazole group (15 [17%] of 88 patients). The difference was 9% (P = .12).
• At 30-day follow-up of 96 (69%) of 139 subjects, new lesion formation was greater in the placebo group (14 [28%] of 50 patients) vs the trimethoprim-sulfamethoxazole group (4 [9%] of 46 patients). The difference was 19% (P = .02).
• Adverse effects were reported by 10 patients in the trimethoprim-sulfamethoxazole group: 4 had nausea, 3 were drowsy or dizzy, 1 had headache and night sweats, 1 had vaginal yeast infection, and 1 had mild allergic reaction.
• 1 patient in the placebo group reported an adverse effect of drowsiness.
• Limitations of the study were loss to follow-up, convenience sample, inability to generalize to children or to persons with compromised immune systems, and lack of standardization of incision-and-drainage technique.
Clinical Implications
• In adults with uncomplicated skin abscesses, trimethoprim-sulfamethoxazole does not decrease treatment failure at 7 days after incision and drainage.
• In adults with uncomplicated skin abscesses, trimethoprim-sulfamethoxazole might decrease the formation of new lesions at 30 days after incision and drainage