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Should antibiotics be used in conjunction with incision and drainage of a simple abscess? Recent studies suggest not, yet they leave room for physician discretion at the bedside.

In last month’s column we discussed a number of issues surrounding the assessment and treatment of abscesses. The literature has indicated that the number of patients presenting for ED care of skin and soft tissue infections has risen substantially over the last 10 years and the ascendancy of methicillin-resistant staphylococcal aureus (MRSA) has made care of these infections more challenging.
Although the fundamentals of care have not changed, there are some important nuances concerning abscesses that were addressed last month:

  • Physicians often cannot distinguish clinically between abscesses and cellulitis
  • Use of ultrasonography can reliably determine if a pocket of pus is present
  • Packing is generally not necessary in the care of incised abscesses and is likely associated with increased pain if repacking is performed
  • Although not commonly performed, there is some literature and rationale supporting the selective suture closing of abscesses after drainage (healing is faster and scars are better looking)


Whether abscesses should be treated with antibiotics in addition to drainage has been a matter of some debate. Although it is unequivocally clear that drainage is the primary treatment of abscesses, the concomitant use of antibiotics varies widely among physicians. Here’s a look at some of the literature on the subject.

First of all, it should be noted that large subsets of the population are often excluded from studies of the value of antibiotics in abscesses that have been drained. Specifically, studies often exclude immunocompromised patients including diabetics and those on steroids. In addition, those at the extremes of age may also be excluded. It is important to be aware of these exclusions in that the goal of studies is to be able to extrapolate the results to the universe of patients who meet the entrance requirements. If physicians don’t specifically know that selected patients were excluded from study, there is the risk of applying the study results to these groups unjustifiably.

Here’s a relatively recent study that makes a number of important points:

  • Both the CDC-P and the Infectious Disease Society of America recommend incision and drainage alone, without antibiotics, for most patients with simple cutaneous abscesses.
  • Community-acquired (CA) MRSA was the cause of the infection in at least half of the patients
  • Outcomes were similar if antibiotics not effective against MRSA were used vs. drainage alone


ARE ANTIBIOTICS NECESSARY AFTER INCISION AND DRAINAGE OF A CUTANEOUS ABSCESS?
Hankin, A., et al, Ann Emerg Med 50(1):49, July 2007

BACKGROUND: Both the CDC-P and the Infectious Diseases Society of America recommend incision and drainage (I&D) alone, without antibiotics, for most patients with a simple cutaneous abscess, and use of an antibiotic effective against MRSA only if the abscess is persistent or recurrent.

METHODS: The authors, from the University of Pennsylvania, reviewed five research studies and one abstract concerning the management of simple abscesses.

RESULTS: Two randomized, controlled trials performed in the 1970s and early 1980s reported no clear advantage of antibiotics in addition to I&D. In one trial published in 2006 and involving patients with comorbidities and at increased risk for MRSA infection, wound cultures were positive for MRSA in 52%. A course of cephalexin following I&D did not significantly improve resolution rates, which exceeded 90% in placebo-treated controls. Similar findings were noted in two prospective studies (one involving children with an abscess culture- positive for MRSA and the other involving adults presenting to a university-affiliated ED in one of eleven U.S. cities [cultures positive for MRSA in nearly half of these latter patients]). In both of these studies, most patients in all treatment groups experienced complete resolution of the abscess after I&D, including those receiving an antibiotic that was ineffective against the causative organism. A retrospective study involving 441 abscesses (64% due to MRSA) reported similar conclusions.

CONCLUSIONS: These findings do not support the routine use of antibiotics, in addition to I&D, in patients with a simple cutaneous abscess, including those residing in an area in which MRSA is prevalent. 8 references (This email address is being protected from spambots. You need JavaScript enabled to view it. ) 11/07 - #10

But what about the “fine” print? What is a “simple” abscess? In their latest recommendations, published in Clinical Infectious Diseases (January, 2011) (Clinical Practice Guidelines by the Infectious Disease Society of America for the Treatment of Methicillin-Resistant Staphylococcus Aureus Infections in Adults and Children) the IDSA takes a more cautious approach. Specifically, they note that “for simple abscesses or boils, incision and drainage alone is likely to be adequate, but additional data are needed to further define the role of antibiotics, if any, in this setting.”

Regarding in what subset of patients antibiotic therapy is advised, they note “antibiotic therapy is recommended for abscesses associated with the following conditions: severe or extensive disease (e.g. involving multiple sites of infection) or rapid progression in presence of associated cellulitis, signs and symptoms of systemic illness, associated comorbidities or immunosuppression, extremes of age, abscess in an area difficult to drain (e.g. face, hand, and genitalia), associated septic phlebitis, and lack of response to incision and drainage alone.” So the IDSA guidelines leave a great deal of wiggle room regarding the use of antibiotics in the setting of abscesses.

When it comes to the choice of antibiotics the IDSA advises that “for empirical coverage of CA-MRSA in outpatients with SSTI (skin and soft tissue infections), oral antibiotic options include the following: clindamycin (A-II), trimethoprim-sulfamethoxazole (TMP-SMX) (A-II), a tetracycline (doxycycline or minocycline) (A-II), and linezolid (A-II). If coverage for both β-hemolytic streptococci and CA-MRSA is desired, options include the following: clindamycin alone (A-II) or TMP-SMX or a tetracycline in combination with a β-lactam (e.g. amoxicillin) (A-II) or linezolid alone (A-II). The bold letters and numbers refer to the levels of evidence supporting the recommendations.

With regard to cellulitis, the IDSA distinguishes between “purulent” and “nonpurulent” cellulitis. “For outpatients with purulent cellulitis (e.g. cellulitis associated with purulent drainage or exudate in the absence of a drainable abscess), empirical therapy for CA-MRSA is recommended pending culture results. Empirical therapy for infection due to β-hemolytic streptococci is likely to be unnecessary (A-II). Five to 10 days of therapy is recommended but should be individualized on the basis of the patient’s clinical response.”

For outpatients with nonpurulent cellulitis (e.g. cellulitis with no purulent drainage or exudate and no associated abscess), empirical therapy for infection due to β-hemolytic streptococci is recommended (A-II). The role of CA-MRSA is unknown. Empirical coverage for CA-MRSA is recommended in patients who do not respond to β-lactam therapy and may be considered in those with systemic toxicity. Five to 10 days of therapy is recommended but should be individualized on the basis of the patient’s clinical response.

Given that the preponderance of the literature indicates that incision and drainage alone is adequate treatment to resolve most “simple” abscesses, are there any potential reasons to prescribe antibiotics for patients with abscesses? Two papers suggest that recurrence rates for abscesses are less when antibiotics are given. The first paper had an atypically high failure rate of initial therapy which may have tainted the conclusions, although the second paper, with a much better initial treatment success rate also noted an increase in recurrences.

RANDOMIZED CONTROLLED TRIAL OF TRIMETHOPRIM-SULFAMETHOXAZOLE FOR UNCOMPLICATED SKIN ABSCESSES IN PATIENTS AT RISK FOR COMMUNITY-ASSOCIATED METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS INFECTION
Schmitz, G.R., et al, Ann Emerg Med 56(3):283, September 2010

BACKGROUND: It has been reported that community-associated methicillin-resistant S. aureus (CA-MRSA) is responsible for more than 50% of skin and soft tissue infections in patients treated at a major US medical center. A cure rate above 90% has been reported with incision and drainage (I&D) without antibiotics.

METHODS: In this double-blind controlled study, coordinated at the Washington (DC) Hospital Center, a convenience sample of 220 immunocompetent patients over the age of 16 who underwent I&D of an uncomplicated skin abscess at one of four military EDs were randomized to a seven-day course of trimethoprim-sulfamethoxazole (TMP-SMX, 160/800) or placebo, given twice daily, and followed to evaluate treatment failure (no improvement after two days, development of a new lesion at seven days, or worsening infection prompting intervention) at seven days or the development of a recurrent lesion by 30 days. RESULTS: MRSA was isolated in 53% of the patients, and was invariably sensitive to TMP-SMX. There was a trend toward less treatment failure at seven days in the TMP-SMX group (17% vs. 26% in controls), and development of a new lesion within 30 days was less common in the patients treated with TMP-SMX (9% vs. 28% in controls).

CONCLUSIONS: There was a trend toward reduced treatment failure at seven days in patients undergoing I&D of an uncomplicated skin abscesses, with adjunctive treatment with TMP-SMX, as well as a decrease in the development of new lesions at 30 days. The interpretation of these findings is clouded, however, by the extremely and unusually high rate of bad outcomes in all patients in this study, regardless of which treatment they received. 11 references (This email address is being protected from spambots. You need JavaScript enabled to view it. - no reprints) 1/11 - #12

RANDOMIZED, CONTROLLED TRIAL OF ANTIBIOTICS IN THE MANAGEMENT OF COMMUNITY-ACQUIRED SKIN ABSCESSES IN THE PEDIATRIC PATIENT
Duong, M., et al, Ann Emerg Med 55(5):401, May 2010

BACKGROUND: There is some debate as to whether antibiotics are required following adequate incision and drainage of a skin abscess caused by community-acquired methicillin-resistant S. aureus (CA-MRSA). METHODS: In this controlled clinical trial, from St. Louis (MO) University, 149 evaluable children aged 3 months to 18 years (median, 4 years) presenting to a pediatric ED with a skin abscess were randomized, after incision and drainage, to a ten-day course of trimethoprim-sulfamethoxazole (10-12mg/kg/day of trimethoprim in two divided doses [maximum 160mg/dose]) or placebo.

RESULTS: There were no differences between the groups in baseline characteristics. About half the children (53%) were below the age of five years and the abscess was most often located in the diaper region. No adverse effect was reported for 81% of the antibiotic group and 88% of controls, and there were no serious adverse effects. CA-MRSA was isolated in 80% of the lesions (clindamycin resistance 18%, 100% sensitivity to TMP-SMX). The treatment failure rate at ten days (any erythema, warmth, induration, fluctuance, tenderness and/or drainage) was not different (4.1% in the TMP-SMX group and 5.3% in controls). Development of a new lesion at 10 days occurred more frequently in controls (26%, vs. 13% of the antibiotic group), but by three months a new lesion had developed in 29% and 28%, respectively.

CONCLUSIONS: The authors suggest that antibiotic treatment does not appear to be necessary after I&D for children presenting with a skin abscess, although antibiotic therapy did tend to reduce the development of new lesions in the short term. 14 references (This email address is being protected from spambots. You need JavaScript enabled to view it. for reprints) 10/10 - #12

The bottom line: there is no compelling evidence that antibiotics alter the initial treatment outcomes in patients with simple abscesses. Recommendations do, however, leave significant room for discretion for such variables as immunocompromise, severity of the process, rate of progression, amount of cellulitis, co-morbidities, concern about recurrence and other factors to determine if antibiotics should be used in conjunction with incision and drainage.

Given that antibiotics are associated with side effects and costs, and the literature generally does not support their use in simple abscesses, it would seem appropriate that clinicians document the reason for the use of antibiotics when they are initially prescribed for the adjunctive treatment of abscesses.

Richard Bukata, MD Editor of Emergency Medical Abstracts (www.ccme.org)


 

 

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