187. Determining Susceptibility Patterns and Prescribing Behaviors Related to a Rapid Diagnostic Tool for Gram Negative Bacteremia
Session: Poster Abstract Session: Diagnostics: Bacteriology, Sequencing, and Resistance
Thursday, October 27, 2016
Room: Poster Hall
  • Verigene GN poster for ID week 2016 10.18.16 FINAL.pdf (937.5 kB)
  • Background: Nanosphere’s Verigene® system is an automated microarray-based, multiplexed assay used on blood cultures positive for aerobic bacterial growth. The Gram negative (GN) panel detects eight organisms and six resistant markers. Since these resistance markers are not all-inclusive, determining the most appropriate treatment based on the results has presented a challenge at Christiana Care Health System (CCHS).

    Methods: This was a retrospective chart review performed on all patients with GN bacteremia whose blood isolate was detected by Verigene® between May and October of 2015 at CCHS. The primary outcome was to determine the percent of isolates testing susceptible to an antibiotic, in an effort to create an antibiogram. Secondary outcomes included the percent of episodes in which antimicrobials were altered after receipt of Gram stain, Verigene®, and susceptibility results.

    Results: Out of 151 GN isolates detected by Verigene®, 90 (60%) were E. coli. There were less than 30 isolates of each other organism detected. The CTX-M and OXA resistance markers were identified 21 and 1 time, respectively. Cefepime, aztreonam, and ceftriaxone susceptibilities for E. coli without resistance markers were 100%, 99%, and 97%, respectively, whereas cefazolin and levofloxacin susceptibilities were less than 80%. In E. coli isolates with CTX-M, imipenem and meropenem were susceptible 100% of the time, while the cephalosporins, fluoroquinolones, and aztreonam were 0% susceptible. Overall, Verigene® guided therapy changes occurred in 86 cases (57% of the time). Of these, 51% were an escalation, 41% were a de-escalation and 8% were lateral changes.

    Conclusion: The susceptibility patterns determined will help guide therapy for future GN Verigene® results. At our institution, ceftriaxone is appropriate for E. coli not expressing CTX-M. Carbapenems should be reserved for isolates expressing resistance, including E. coli CTX-M. The small numbers of other organisms limit the applicability of these results in clinical practice until additional data is collected. Implementation of the GN Verigene® platform has impacted prescribing patterns for patients with GN bacteremia, which may lead to patients receiving more targeted therapy sooner.

    Julianne Gardner, PharmD, Nicole Harrington, PharmD, BCPS, Alexis Gross, PharmD and Jennifer Lukaszewicz, PharmD, Christiana Care Health System, Newark, DE


    J. Gardner, None

    N. Harrington, None

    A. Gross, None

    J. Lukaszewicz, None

    Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.