Students in the fourth year family medicine clerkship are expected to write a Health Desk Answer (HDA) during the rotation. Many of these answers go on to be published. HelpDesk Answers (HDAs) are brief, structured evidence-based answers to clinical questions written by physicians for physicians. HDAs are peer reviewed and published in Evidence-Based Practice, a monthly journal produced by the Family Physicians Inquiries Network (FPIN) and distributed to more than 4,000 physicians and libraries, world-wide.
Title: Antibiotics for treatment of abscesses
Authors: Jonathan M. Budzik, PhD, Umang Sharma, MD
Affiliation: University of Chicago Pritzker School of Medicine, Chicago, IL
Word Count: 602, including references
Question: Following incision & drainage, are antibiotics indicated for the treatment of uncomplicated abscesses?
Evidence-Based Answer
The use of antibiotics following incision and drainage (I&D) does not improve cure rates when compared to I&D alone. This is true even in settings with high rates of methicillin-resistant Staphylococcus aureus (MRSA) infection. (SOR A, based on multiple consistent randomized controlled trials [RCTs])
Evidence Summary
Skin and soft tissue infections (SSTI) are commonly treated with antibiotics after incision and drainage.1 However, increasing antimicrobial use raises concerns about resistance, side effects, and cost. Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of SSTIs and was cultured from 53-80% of abscesses in the 3 RCTs discussed here. In these studies, treatment failure was defined as a lack of clinical improvement or the requirement of additional interventions due to worsening clinical status.
The first RCT was a non-inferiority study comparing antimicrobial treatment to placebo in 161 afebrile, otherwise healthy pediatric patients with abscesses, 80% of which were attributed to MRSA.2 After I&D, patients received either trimethoprim-sulfamethaxozole (TMP-SMX; 10-12 mg/kg/day TMP) or placebo for 10 days. Compliance rates were low in both arms (46% TMP/SMX and 55% placebo). Failure rates were 5.3% (4/76) in the placebo group and 4.1% (3/73) in the antibiotic group (difference not significant).
Another RCT assigned 212 afebrile, healthy adults with abscesses to either 7 days of TMP-SMX 160 mg/800 mg twice a day or placebo after I&D.3 There was no significant difference between the groups in failure rates after 7 days (26% in placebo group vs. 17% in the antibiotic group (risk reduction 9%; 95% CI -2% to 21%; P=0.12). MRSA was identified in 53% of these abscesses.
A third RCT studied 166 outpatient adults with abscesses, including those with comorbidities such as HIV infection, diabetes mellitus, and drug use.4 Patients were treated with I&D and cephalexin 500 mg four times a day or placebo for 7 days. Clinical cure rate was 90.5% (76/84) in the placebo group and 84.1% (69/82) in the cephalexin group with an absolute difference of 6.4% 95% (CI of -4.2 to 17.0).5 This study was limited by ineffective antibiotic selection for the treatment group because about 60% of the abscesses were caused by MRSA, which is not susceptible to cephalexin. However, clinical cure rates were high in both groups.
References
1. Tiara BR, Singer AJ, Thode HC Jr, Lee CC. National epidemiology of cutaneous abscesses: 1996 to 2005. Am J Emerg Med. 2009; 27(3):289-292. [LOE 2c]
2. Duong M, Markwell S, Peter J, Barenkamp S. Randomized, controlled trial of antibiotics in the management of community-acquired skin abscesses in the pediatric patient. Ann Emerg Med. 2010; 55(5):401-407. [LOE 1b]
3. Schmitz GR, Bruner D, Pitotti R, Olderog C, Livengood T, Williams J, Huebner K, Lightfoot J, Ritz B, Bates C, Schmitz M, Mete M, Deye G. Randomized controlled trial of TMP-SMX for uncomplicated skin abscesses in patients at risk for CA-MRSA infection. Ann Emerg Med. 2010; 56(3):283-287. [LOE 2b]
4. Rajendran PM, Young D, Maurer T, Chambers H, Perdreau-Remington F, Ro P, Harris H. Randomized, double-blind, placebo-controlled trial of cephalexin for treatment of uncomplicated skin abscesses in a population at risk for CA-MRSA infection. Antimicrob Agents Chemother. 2007; 51(11):4044-4048. [LOE 1b]
5. Chambers HF. Incision and Drainage Alone. N Engl J Med. 2008; 359(10): 1063-1064. [LOE 5]
Continuing Education Question
Which of the following statements about uncomplicated skin abscesses is true?
a. If a patient has risk factors for MRSA, treatment with TMP-SMX or clindamycin is appropriate.
b. Most skin abscesses are caused by methicillin-susceptible Staphylococcus aureus (MSSA).
c. Anti-MSSA therapy, such as a cephalosporin, is indicated for initial treatment of skin abscesses.
d. Incision and drainage alone is sufficient therapy.