Antibiotic Prescribing Practices among Patients Hospitalized with Acute Bacterial Skin and Skin Structure Infection: Results of a Multi-Center Study

Background:   Acute bacterial skin and skin structure infections (ABSSSI) are one of the most common infections resulting in hospitalization.  Although ABSSSI can be treated with short courses of antibiotics targeting Gram-positive bacteria, recent single-center studies showed that antibiotic overuse is common.  The objectives of this study were to evaluate antibiotic prescribing practices for ABSSSI and factors affecting prescribing across a diverse group of hospitals.

Methods:   This was a retrospective cohort study of patients hospitalized for ABSSSI during June 2010 – May 2012 in seven community and academic hospitals.  Up to 85 cases at each site were reviewed and classified as non-purulent cellulitis, purulent cellulitis or wound infection, or major cutaneous abscess.  The primary outcome was a composite of two markers of antibiotic overuse:  1) prescription of antibiotics with broad gram-negative activity, or 2) prolonged treatment duration (>10 days). 

Results: Of 492 eligible patients, 293 had non-purulent cellulitis, 44 had purulent cellulitis or wound infection, and 155 had major abscess.  The median age was 47 years; 102 (21%) were ≤18 years.  Prior skin infection (136, 28%) and diabetes mellitus (92, 19%) were common risk factors.  The predominant site of infection was the lower extremity (296, 60%).  Despite isolation of Gram-negative microorganisms in only 12 (3%) of 385 cases with blood, abscess, or tissue cultures, broad gram-negative antibiotics were prescribed in 44% (range 22-64% across hospitals) and accounted for 39% of the total antibiotic-days prescribed.  Use of broad gram-negative or prolonged therapy occurred in 77% (range 61-95%) of cases and varied significantly across hospitals (p<.001).  By multivariate logistic regression, factors associated with broad gram-negative or prolonged therapy included head or neck involvement (odds ratio [OR] 2.7, 95% confidence interval [CI] 1.1 – 6.5), adult (vs. pediatric) cases (OR 2.2, 95%CI 1.2 – 3.8), and increasing length of hospital stay (OR 1.5 per day, 95%CI 1.2 – 1.7).

Conclusion:   Among patients hospitalized for ABSSSI, antibiotic overuse is widespread.  Given the frequency of ABSSI, interventions to promote shorter courses of therapy targeting Gram-positive pathogens should be an antimicrobial stewardship priority.