236. Carbapenem Stewardship: Improved and Sustained Susceptibility of Pseudomonas aeruginosa to Imipenem Correlated with Eight-Years of Increasing Ertapenem Usage
Session: Poster Abstract Session: Antimicrobial Stewardship in Clinical Practice
Friday, October 21, 2011
Room: Poster Hall B1
  • Ertapenem poster IDSA 2011.4.pdf (961.7 kB)
  • Background: Because selective pressure can result in resistance, we studied our eight year experience with ertapenem and imipenem usage on the in vitro activity of imipenem against Pseudomonas aeruginosa and Enterobacteriaecae to see if early gains (2002-2005) in P. aeruginosa susceptibility to imipenem were sustained for an additional 5 years.

    Methods: We retrospectively analyzed antimicrobial usage (defined daily dose/ 1,000 patient days; DDD) for ertapenem, imipenem, levofloxacin, piperacillin-tazobactam and cefepime and their antimicrobial susceptibilities (except ertapenem) for P. aeruginosa, and Enterobacteriaceae from August 2002 until September 2010. Time series analysis was used to statistically evaluate for any changes.

    Results:  Ertapenem usage rose steadily to 48 DDD at three years and to 85.4 DDD at eight years. Imipenem usage gradually declined with the increased ertapenem usage and ranged from 29.3 DDD at three years to 19 DDD at eight years.  Levofloxacin usage declined (from 246 DDD to 149 DDD) coincident with reduced susceptibilities of levofloxacin. Cefepime and piperacillin-tazobactam usage was relatively constant.  P. aeruginosa susceptibility to imipenem was 73% pre-study and steadily rose to 88% (median, intraquartile range 82-95%) at three years (2005) and was sustained at the 88% level (median, 83-97% intraquartile range) for the ensuing five years of study. Imipenem maintained almost 100% activity against Enterobacteriaceae. ESBL enzymes were present in 1% of E. coli prior to the introduction of ertapenem and rose to 3% in 2010, while it remained at 4% for K. pneumoniae during the entire period

    Conclusion: Improved imipenem susceptibilities for P. aeruginosa were sustained at 88% and were unaffected by increased ertapenem usage over an eight-year period.

    Subject Category: J. Clinical practice issues

    Ellie Goldstein, MD, FIDSA1, Victoria Peraino, BS2, Lisa Hammer-Rieg, PharmD3, Diane Citron4 and Tanya Elgort, PharmD3, (1)RM Alden Res Lab, Santa Monica, CA, (2)St Johns' Health Center, Santa Monica, CA, (3)Pharmacy, St Johns Health Center, Santa Monica, CA, (4)R.M. Alden Research Laboratory, Culver City, CA


    E. Goldstein, Merck & Co: Research Contractor, Scientific Advisor and Speaker's Bureau, Consulting fee, Research grant and Speaker honorarium

    V. Peraino, None

    L. Hammer-Rieg, None

    D. Citron, None

    T. Elgort, 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.