378. Daptomycin Non-susceptible Enterococcus faecium: Emerging Pathogen or Microscan™ Pseudo-Phenomenon?
Session: Poster Abstract Session: MRSA, MSSA, Enterococci
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
  • IDW Poster Final.pdf (345.9 kB)
  • Background: Although reported rates of daptomycin non-susceptible Enterococcus (DNSE) isolates remain low (0.3% of isolates from 2002-08 US surveillance data), recent publications suggest a higher occurrence. At Lahey Hospital & Medical Center (LHMC), emergence of DNSE (MIC > 4 mg/mL) increased from 0% of initial E. faecium isolates tested in 2008 to 17% in 2010, then 12% in 2012.

    Methods: We reviewed all patients with DNSE identified by Microscan™ from 1 Jan 2008 to 31 Dec 2012. DNSE susceptibility was verified by E-test at LHMC and by broth dilution MIC and E-test at Cubist Pharmaceuticals, Lexington, MA. Patient isolates sorted into 3 categories: confirmed DNSE (MIC > 4 mg/mL in Microscan™ and by another test), non-confirmed DNSE (MIC > 4 mg/mL for Microscan™ but MIC ≤ 4 mg/mL in all other tests), and isolates unavailable for confirmatory testing (MIC > 4 mg/mL in Microscan™ only).

    Results: 99 patients (126 isolates) from 2008 to 2012 with DNSE were reviewed. Of 50 patient isolates available for additional testing, 21 had confirmed and 29 had non-confirmed DNSE.  DNSE was hospital-acquired in 43% of inpatients (>3 days from admission to positive culture). Two DNSE isolates were also resistant to linezolid and vancomycin.

    Of patients with confirmed DNSE, 86% were inpatients. 43% had hepatobiliary disease and/or procedures. 57% and 29% of first isolates of DNSE were in urine and blood cultures, respectively. 76% of patients had antibiotic exposure within 30 days prior to positive DNSE culture: 57%, 57%, and 24% received cefepime, vancomycin, and daptomycin, respectively.

    Patients with confirmed DNSE were not statistically different in characteristics from non-confirmed DNSE patients or those with no confirmation data.  Treatment changed to linezolid following report of DNSE in 29 patients. All groups had similar mortality (21.8% died or were discharged to hospice).  

    Conclusion: Rates of DNSE rose rapidly at LHMC from 2008 to 2012. It is unclear whether isolates deemed resistant by Microscan™ are truly daptomycin-non-susceptible or represent a pseudo-phenomenon. However, we were unable to distinguish between non-confirmed and confirmed DNSE. In practice, reports of DNSE generated frequent linezolid use, raising the potential risk of combined resistance to daptomycin, linezolid, and vancomycin.

    Jacqueline M. Mills, MPP1,2, Deanna Rossi, PharmD3, Elizabeth O'Gara, PharmD4, Wendy Gillespie, MT, ASCP5, Eva Piessens, MD, MPH6 and Robert Duncan, MD, MPH2, (1)Tufts University, Medford, MA, (2)Lahey Clinic, Burlington, MA, (3)Pharmacy, Cambridge Health Alliance, Cambridge, MA, (4)Pharmacy, Lahey Clinic Medical Center, Burlington, MA, (5)Microbiology, Lahey Clinic, Burlington, MA, (6)Infectious Diseases, Lahey Clinic Medical Center, Burlington, MA


    J. M. Mills, None

    D. Rossi, None

    E. O'Gara, None

    W. Gillespie, None

    E. Piessens, None

    R. Duncan, None

    Findings in the abstracts are embargoed until 12:01 a.m. PST, Oct. 2nd with the exception of research findings presented at the IDWeek press conferences.