Reviewed by Dr. Adrian Peña
Daum, R, et al. N Engl J Med. 2017 Jun 29; 376(26):2545-2555

SUMMARY
This multicenter, double-blind, randomized controlled trial evaluated 786 patients (505 adults and 281 children) with small skin abscesses (≤5cm, smaller size for pediatric patients) that were randomized to undergo incision and drainage plus either clindamycin (300mg every 8 hours), trimethoprim-sulfamethoxazole (TMP-SMX; 160mg/800mg every 12 hours) or placebo for 10 days. The primary outcome was cure at 7-10 days after the end of treatment; secondary outcomes included cure at 1 month, occurrence of new infections, and rate of treatment-associated adverse events.

Cure rates at 7-10 days were significantly higher in the clindamycin group (83%) and in the TMP-SMX group (82%) as compared to placebo (69%; p<0.0001 for both groups). There was no significant difference in the cure rates between the clindamycin and TMP-SMX groups (p=0.73). Subgroup analyses revealed that this beneficial effect was mainly driven by response in patients with culture-proven S. aureus infection (cure rates 84% with clindamycin and 83% with TMP-SMX, versus 63% with placebo; p<0.001 for both comparisons), including those with culture-proven MRSA infection (cure rates 82% with clindamycin and 85% with TMP-SMX, versus 63% with placebo; p=0.001 and p<0.001, respectively). Cure rates in patients with pathogens other than S. aureus and those in whom cultures were negative were similar among the three treatment groups (p=0.99 for all comparisons).

At 1-month follow-up, cure rates for both clindamycin (79%) and TMP-SMX (73%) groups were significantly higher than placebo (63%; p<0.001 and p=0.01, respectively). New infections were more common after TMP-SMX (14%) and placebo (12%) than after clindamycin therapy (7%; p=0.03 and p=0.06, respectively). Adverse events were more common with clindamycin (22%) than with TMP-SMX (11%) or placebo (13%).

COMMENTARY
Uncomplicated skin abscess is commonly seen in the outpatient setting and in the emergency room, with the incidence increasing due to community acquired methicillin-resistant Staphylococcus aureus (CA-MRSA).1,2 Current guidelines regarding the treatment of cutaneous abscess do not recommend the routine use of antibiotics following incision and drainage procedure unless signs of systemic infection, significant co-morbidities or recurrent infection are present.1,2 This recommendation is driven largely by expert opinion given the lack of high-quality trials in this area.

This study, along with another randomized trial of TMP-SMX versus placebo,3 suggests that there may be a beneficial role for systemic antibiotics in improving cure rates following incision and drainage. On the other hand, there were no clinically deleterious adverse events in the placebo group, suggesting that low risk patients with small abscesses (<2 cm) may not necessarily need systemic antibiotic therapy following drainage of the abscess, provided they are followed closely. Of note, this study excluded patients at higher risk of complicated infection including those with systemic symptoms, involvement of delicate areas (e.g. perirectal, genital, or hand infection), bites, immunosuppressive conditions, and surgical site or prosthetic device infection. In such patients, withholding antibiotic therapy may lead to worse clinical outcomes.

REFERENCES
1. Schmitz GR, Bruner D, Pitotti R, et al. Randomized controlled trial of trimethoprim-sulfamethoxazole for uncomplicated skin abscesses in patients at risk for community-associated methicillin-resistant Staphylococcus aureus infection. Ann Emerg Med 2010; 56:283–7.
2. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis 2014;59(2): e10-e52.
3. Talan DA, Mower WR, Krishnadasan A, et al. Trimethoprim–sulfamethoxazole versus placebo for uncomplicated skin abscess. N Engl J Med 2016;374:823-32.

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