303. Excessive Antibiotic Exposure in Uncomplicated Skin and Soft Tissue Infections in the Ambulatory Care Setting
Session: Poster Abstract Session: Antimicrobial Therapy: Clinical Studies
Friday, October 21, 2011
Room: Poster Hall B1
Background:  Ambulatory care visits for skin and soft tissue infections (SSTI) have increased dramatically.  Ensuring optimal antibiotic prescribing in such cases is therefore essential to antibiotic stewardship efforts.  The objectives of this study were to describe prescribing patterns and identify opportunities to decrease unnecessary antibiotic exposure.

Methods:  We performed a retrospective cohort study of adults and children with uncomplicated SSTI treated in ambulatory care sites of a public safety net healthcare system in Denver, Colorado.  A random sample of cases between Mar 1, 2010 and Feb 28, 2011 were abstracted and classified as cellulitis, wound infection, or cutaneous abscess.  The primary outcome was excessive antibiotic exposure, defined as broad gram-negative, combination, or prolonged (≥10 days) antibiotic therapy. 

Results:  Of 670 cases reviewed, 356 met criteria for uncomplicated cellulitis (148, 42%), wound infection (41, 12%), or abscess (167, 47%).  Upper or lower extremities were involved in 113 (32%) and 115 (32%) cases, respectively.  Plain films were obtained in 47 (13%).  A microorganism was cultured in 67 cases, with staphylococci or streptococci in 64 (96%).  In total, 315 (88%) patients received an antibiotic.  The most common regimens were trimethoprim-sulfamethoxazole (TMP-SMX) (115, 32%), cephalexin (67, 19%), doxycycline (53, 15%), or cephalexin plus TMP-SMX (44, 12%).  MRSA-active drugs were used in 87 (60%) cases of cellulitis, 22 (58%) wound infections, and 124 (93%) abscesses when an antibiotic was prescribed.  The median duration of therapy for all cases was 7 days (IQR 7-10). The primary endpoint of excessive antibiotic exposure occurred in 124 (35%) and was common across all 3 classifications.  In multivariate analysis, only cellulitis (versus abscess) and wound infection (versus abscess) were independently associated with excessive antibiotic exposure with odds ratios [95%CI] of 1.62 [1.03-2.57] and 2.32 [1.20-4.49], respectively.  Clinical failure occurred in 44 (12%) cases. 

Conclusion:  Excessive antibiotic exposure in uncomplicated SSTIs is common, particularly use of combination therapy and prolonged treatment.  Interventions to promote short courses of single-agent gram-positive therapy are needed.

Subject Category: C. Clinical studies of bacterial infections and antibacterials including sexually transmitted diseases and mycobacterial infections (surveys, epidemiology, and clinical trials)

Hermione Hurley, MBChB1, Bryan Knepper, MPH, MSc2, Connie Price, MD2, Claire Swartwood, PharmD2, Philip Mehler, MD2, William Burman, MD2 and Timothy Jenkins, MD2, (1)Exempla St. Joseph Hospital, Denver, CO, (2)Denver Health Medical Center, Denver, CO


H. Hurley, None

B. Knepper, None

C. Price, None

C. Swartwood, None

P. Mehler, None

W. Burman, None

T. Jenkins, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.