397. Not Daptomycin's Fault? Potential Nosocomial Transmission of Daptomycin Non-Susceptible Enterococci
Session: Poster Abstract Session: MRSA, MSSA, Enterococci
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
Background: Surveys of antimicrobial resistance since daptomycin (DAP) was introduced into clinical practice have demonstrated low rates of DAP non-susceptible enterococci (DNSE). When observed, DNSE typically emerge in patients treated with extended courses of DAP. However, nosocomial transmission of DNSE has not been widely described in the literature to date. Here we describe a cluster of DNSE at a tertiary care center and explore evidence for nosocomial transmission.

Methods: DAP susceptibility testing was performed using E-test; non-susceptibility was defined as DAP MIC >4 μg/mL per CLSI guidelines. Incidence rate (per 10,000 patient-days) and prevalence during the pre-outbreak (3/2/10-12/23/12) and outbreak (12/24/12-4/16/13) periods were compared. Clinical information, antibiotic usage, and bed tracing were obtained from electronic medical records and existing databases. 

Results: During the pre-outbreak period, the incidence of DNSE was 0.22 cases per 10,000 patient-days and the prevalence of DNSE was 0.11%. During the outbreak period, the incidence of DNSE was 1.99 cases per 10,000 patient-days (p<0.0001) and the prevalence of DNSE was 0.51%.

Antibiotic exposure was reviewed for all patients. Of the 11 pre-outbreak patients, 9 (82%) received DAP prior to isolation of DNSE (median 14 days, range 0-68). Of the 11 outbreak patients, 4 (36%) received DAP prior to isolation of DNSE (median 0 days, range 0-26).  The median number of days hospitalized (in the past 90) prior to isolation of DNSE was 67 in the pre-outbreak group and 37 in the outbreak group.

The pre-outbreak patients developed DNSE while on 6 distinct units separated in time, whereas 9 of 11 patients in the outbreak were epidemiologically linked in space (spanning 7 units) and time.

Conclusion: DAP non-susceptibility among enterococci is rare but may emerge during treatment with DAP. These data suggest that acquisition of DNSE may occur through nosocomial transmission in addition DAP selection pressure, which has important implications for infection control and antibiotic stewardship practices.

Jessica Lewis, MD1, Amy Mathers, MD1, Heather Cox, PharmD1, Kyle Enfield, MD MS2 and Costi D. Sifri, MD1, (1)Division of Infectious Diseases and International Health, University of Virginia Health System, Charlottesville, VA, (2)Hospital Epidemiology/Infection Prevention and Control, University of Virginia Health System, Charlottesville, VA

Disclosures:

J. Lewis, None

A. Mathers, None

H. Cox, None

K. Enfield, None

C. D. Sifri, None

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