Future medical historians will report that arachnophobia became an infectious disease in 2002. Around that time, a CDC public health dispatch (MMWR 2003;52:88) warned of an epidemic of skin lesions in Los Angeles County Jail inmates thought initially to have resulted from a spider infestation. Subsequently these “spider bites” proved instead to be one of the earliest documented outbreaks of community acquired-methicillin resistant Staphylococcus aureus (CA-MRSA), but the damage to the collective arachnid reputation had already been done.
Over the years, however, CA-MRSA began to develop a reputation of its own. Reports of the ever increasing incidence of MRSA in the medical literature combined with high-profile outbreaks in athletes and previously healthy children had us wondering if the media were correct in elevating MRSA to “superbug” status. (Ann Emerg Med 2008;51:299.)
Yet, despite MRSA's notoriety, ubiquity, and its well-documented biochemical mechanisms of increased virulence, cutaneous MRSA has remained fairly easy to treat over the years with a relatively low incidence of serious complications in otherwise healthy hosts.
In 2006, an epidemiological study by the EMERGEncy ID Net Study Group found the incidence of MRSA in ED patients presenting with purulent skin infections to be 57 percent. (N Engl J Med 2006;355:666.) Although not specifically a goal of this study, an even more interesting finding was that after incision and drainage (I&D), the likelihood of curing a MRSA abscess appeared to be independent of the chosen antibiotic's activity against MRSA!
Shortly after, the authors of a clinical controversy piece in the Annals of Emergency Medicine concluded that the majority of simple cutaneous abscesses (even those caused by MRSA) could be completely cured by I&D alone and that antibiotics were probably not necessary. (Ann Emerg Med 2007;50(1):66.) Recently, more data have emerged to support this premise.
In 2009, a small randomized placebo-controlled trial of 161 pediatric patients with cutaneous abscess (80% CA-MRSA isolates) concluded no difference after I&D in cure rate between patients treated with trimethoprim-sulfamethoxazole vs. placebo. (Ann Emerg Med 2010;55:401.)
Randomized Controlled Trial of Trimethoprim-Sulfamethoxazole for Uncomplicated Skin Abscesses in Patients at Risk for Community–-Associated Methicillin Resistant Staphylococcus aureus Infection
Schmitz GR, Bruner D, et al
Ann Emerg Med
In a recent issue of the Annals of Emergency Medicine, Schmitz et al reported on their trial treating cutaneous abscesses in more than 200 military recruits, a group considered high risk for developing infection with CA-MRSA. Only patients with uncomplicated abscesses were enrolled. Exclusion criteria were reasonable and notable for immunocompromise (e.g., DM, HIV), associated fever or signs of systemic illness, antibiotic use during the previous week, facial abscess, or abscesses requiring operating room drainage. All enrolled patients first underwent incision and drainage. After I&D, patients were randomized for treatment with seven days of either trimethoprim-sulfamethoxazole or placebo.
Overall, 53 percent of enrolled patients were found to have CA-MRSA with 100 percent of these isolates being sensitive to trimethoprim-sulfamethoxazole. Median abscess size was similar in each group (treatment: 2.5 cm, placebo: 2.8 cm) and median diameter of associated cellulitis was also similar (treatment: 4.5 cm, placebo 5.0 cm). Both groups included some patients with abscesses greater than 5 cm (treatment: 6%, placebo: 10%). Consistent with results from the aforementioned studies, patients had no statistically significant difference in treatment failure at seven days.
Additional lesions at 30 days occurred less frequently in the antibiotic group, but this was a secondary outcome limited by large patient dropout. The study also had some additional limitations, including a relatively small sample size, different methods between participating centers, and inadequate information on the ultimate cure of these infections. The authors concluded that adult patients with simple uncomplicated cutaneous abscess drained in the ED followed by treatment with placebo did no worse than patients treated with trimethoprim-sulfamethoxazole.
Presently, the STOP MRSA study group, under a grant from the NIH, is conducting a large multicenter trial which hopefully will remove any remaining doubt regarding this seemingly controversial issue. But from this author's standpoint, there is enough supportive data out there to influence our practice today.
Antibiotics after cutaneous I&D should be reserved only for complicated cases or for patients with concerning clinical features such as immunocompromise, extensive cellulitis, facial involvement, or systemic signs or symptoms. Incision, drainage, and good follow-up, not antibiotics, is the definitive treatment of the uncomplicated cutaneous abscess, even when CA-MRSA is highly suspected or even known to be the culprit. After I&D, patient education regarding wound care, keeping lesions dry and covered, and proper hand hygiene is probably more likely to prevent long-term recurrence than treating with antibiotics. If your colleagues, staff, or patients still insist on antibiotic therapy for these cases, you can feel confident that drain-o-mycin is by far the most effective, inexpensive, and safest choice.
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Journal Scan's Back!
Journal Scan returns to our pages this month with a fresh perspective and new authors but the same critical analysis and bold opinions you always count on from EMN.
This review of the latest studies will focus on practice-changing ideas and trends in emergency medicine. Although Living with the LLSA will no longer appear, Luis Lovato, MD, and his team return with Journal Scan, bringing scrutiny and insight to the science of emergency medicine.