253. Potential Impact of Recommended Changes to Reporting Cephalosporin Minimum Inhibitory Concentrations for Extended Spectrum beta-Lactamase (ESBL) Pathogens
Session: Poster Abstract Session: Antimicrobial Susceptibility and Resistance
Friday, October 21, 2011
Room: Poster Hall B1
Background: The Clinical Laboratory Standards Institute (CLSI) has recommended cephalosporin breakpoint changes for ESBL pathogens.  The number of patients who could receive cephalosporins based on these recommendations and the potential cost savings are unknown.

Methods: We searched the microbiology laboratory database for ESBL pathogens whose minimum inhibitory concentrations (MIC) met new CLSI recommendations for “susceptible” (blood and urine cultures) and “intermediate” (urine cultures only).  Hospitalized patients were identified by positive urine and blood specimens collected between January and October 2010.  Patients were included if they completed therapy with a carbapenem.  Patients were excluded if they were treated with a non-carbapenem agent or were considered colonized.  Data collected included the duration and location of final treatment (inpatient versus outpatient), cephalosporin MICs and specimen source. The potential cost savings was calculated by comparing a cephalosporin regimen against the carbapenem regimen in those deemed cephalosporin susceptible. 

Results:  Using susceptibility breakpoints from the new guidelines, cephalosporin susceptibility was identified in 94 ESBL positive clinical isolates during the study period.  Thirty-two patients had 37 confirmed separate infections.  A carbapenem was used as final treatment in 21 infections (12 bacteremias and 9 urinary tract) and 86% completed therapy in the hospital. No organisms were susceptible to an oral cephalosporin using surrogate markers (cefazolin and ceftriaxone) and cefpodoxime results. Seventeen of the infections met the new criteria for susceptibility to cefepime . The calculated potential savings of a dose adjusted cefepime containing regimen was $16,102 for the 17 patients.

Conclusion:  Based on the new CLSI recommendations a large proportion of our carbapenem treated patients could have received cefepime for the treatment of their ESBL infection.  These recommendations provide additional therapeutic options and also a potential cost savings. Prospective studies will be needed to ensure equivalent efficacy and outcomes of cephalosporins compared to carbapenems in ESBL infections.

Subject Category: A. Antimicrobial agents and Resistance

Mihai Iliesiu, MD1, Sugantha Iyer, MD2, Anilrudh Venugopal, MD2, Shrutika Vasudeva3 and Joel Fishbain, MD4, (1)Internal Medicine, St John Hospital and Medical Center, Grosse Pointe Woods, MI, (2)St. John Hospital and Medical Center, Grosse Pointe Woods, MI, (3)Saint George's University School of Medicine, St Clair Shores, MI, (4)Medicine, St. John Hospital and Medical Center, Grosse Pointe Woods, MI


M. Iliesiu, None

S. Iyer, None

A. Venugopal, None

S. Vasudeva, None

J. Fishbain, 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.