Deviating from IDSA treatment guidelines for non-purulent skin infections increases the risk of treatment failure in emergency department patients.

The Infectious Disease Society of America (IDSA) publishes guidelines regularly for the management of skin and soft tissue infections; however, the extent to which practice patterns follow these guidelines and if this can affect treatment failure rates is unknown. We observed the treatment failure rates from a multicentre retrospective ambulatory cohort of adult emergency department patients treated for a non-purulent skin infection. We used multivariable logistic regression to examine the role of IDSA classification and whether adherence to IDSA guidelines reduced treatment failure. A total of 759 ambulatory patients were included in the cohort with 17.4% failing treatment. Among all patients, 56.0% had received treatments matched to the IDSA guidelines with 29.1% over-treated, and 14.9% under-treated based on the guidelines. After adjustment for age, gender, infection location and medical comorbidities, patients with a moderate infection type had three times increased risk of treatment failure (adjusted risk ratio (aRR) 2.98; 95% confidence interval (CI) 1.15-7.74) and two times increased risk with a severe infection type (aRR 2.27; 95% CI 1.25-4.13) compared with mild infection types. Patients who were under-treated based on IDSA guidelines were over two times more likely to fail treatment (aRR 2.65; 95% CI 1.16-6.05) while over-treatment was not associated with treatment failure. Patients ⩾70 years of age had a 56% increased risk of treatment failure (aRR 1.56; 95% CI 1.04-2.33) compared with those <70 years. Following the IDSA guidelines for non-purulent SSTIs may reduce the treatment failure rates; however, older adults still carry an increased risk of treatment failure.