Improved healing for drained skin abscesses with trimethoprim-sulfamethoxazole

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Trimethoprim-sulfamethoxazole treatment was associated with improved outcomes in patients with drained skin abscesses regardless of lesion size or guideline criteria, according to a study by researchers at the David Geffen School of Medicine at the University of California – Los Angeles (UCLA) and the Olive View–UCLA Medical Centre.

Two large trials in the US recently showed that patients with skin abscesses receiving primary treatment (drainage) had improved outcomes when also treated with trimethoprim-sulfamethoxazole.

The follow-up analysis tested whether these improved outcomes persisted among subgroups with and without conditions for which antibiotics have been selectively recommended.

The subgroups selected for analysis were patients with abscess cavity or erythema maximal dimension ≥5 cm; those with history of methicillin-resistant Staphylococcus aureus (MRSA) infection; patients with fever, diabetes, or major comorbidities such as eczema or chronic oedema, chronic obstructive pulmonary disease, congestive heart failure, HIV infection, or cancer; and patients with positive culture for MRSA or methicillin-susceptible S aureus.

The primary outcomes were the difference in abscess clinical cure rates, defined here as the resolution of all symptoms and signs of infection, or improvement so that no additional antibiotic medications were prescribed any time 7 to 14 days after treatment ended.

Overall 92.9% of patients receiving trimethoprim-sulfamethoxazole achieved the primary outcome, whereas this occurred in only 85.7% of the placebo group, a difference of 7.2 (95% CI, 3.2-11.2). Cure rates remained higher for the treatment group compared with the placebo group in each of the clinical subgroups.

The improved outcomes were seen regardless of abscess or erythema dimensions, but the greatest cure effect was seen in subgroups identified by guidelines for antibiotic treatment, such as those with history of MRSA infection and fever. Further study could validate these findings and lead to improved decision making between clinicians and patients regarding treatment options and costs.

Study objective: Two large randomized trials recently demonstrated efficacy of methicillin-resistant Staphylococcus aureus (MRSA)–active antibiotics for drained skin abscesses. We determine whether outcome advantages observed in one trial exist across lesion sizes and among subgroups with and without guideline-recommended antibiotic indications.
Methods: We conducted a planned subgroup analysis of a double-blind, randomized trial at 5 US emergency departments, demonstrating superiority of trimethoprim-sulfamethoxazole (320/1,600 mg twice daily for 7 days) compared with placebo for patients older than 12 years with a drained skin abscess. We determined between-group differences in rates of clinical (no new antibiotics) and composite cure (no new antibiotics or drainage) through 7 to 14 and 42 to 56 days after treatment among subgroups with and without abscess cavity or erythema diameter greater than or equal to 5 cm, history of MRSA, fever, diabetes, and comorbidities. We also evaluated treatment effect by lesion size and culture result.
Results: Among 1,057 mostly adult participants, median abscess cavity and erythema diameters were 2.5 cm (range 0.1 to 16.0 cm) and 6.5 cm (range 1.0 to 38.5), respectively; 44.3% grew MRSA. Overall, for trimethoprim-sulfamethoxazole and placebo groups, clinical cure rate at 7 to 14 days was 92.9% and 85.7%; composite cure rate at 7 to 14 days was 86.5% and 74.3%, and at 42 to 56 days, it was 82.4% and 70.2%. For all outcomes, across lesion sizes and among subgroups with and without guideline antibiotic criteria, trimethoprim-sulfamethoxazole was associated with improved outcomes. Treatment effect was greatest with history of MRSA infection, fever, and positive MRSA culture.
Conclusion: Treatment with trimethoprim-sulfamethoxazole was associated with improved outcomes regardless of lesion size or guideline antibiotic criteria.

David A Talan, Gregory J Moran, Anusha Krishnadasan, Fredrick M Abrahamian, Frank Lovecchio, David J Karras, Mark T Steele, Richard E Rothman, William R Mower

Infectious Disease Advisor material
Annals of Emergency Medicine abstract

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