873. Daptomycin Non-Susceptible Enterococcus infections can develop in the absence of prior antimicrobial exposure 
Session: Oral Abstract Session: Antimicrobial Resistance and Susceptibility
Saturday, October 22, 2011: 11:00 AM
Room: 151AB
Background: 

Data on exposure to antibiotics before development of daptomycin nonsusceptibility among enterococci remain limited.

Methods: 

We retrospectively reviewed 22 cases of infections associated with DNSE (defined as daptomycin MIC >4 ug/ml by the Clinical Laboratory Standards Institute [CLSI], 2003) identified at a tertiary center from January 2007-March 2011. Cases were evaluated for exposure to antimicrobials in the 3 months before isolation of DNSE. The genetic relatedness of 16 DNSE isolates was determined by rep-PCR using a semi-automated system (DiversiLab, bioMerieux, Durham NC).

Results: 

Antimicrobials associated with development of VRE including vancomycin, third generation cephalosporin and agents with activity against anaerobes had been administered to 15 (68.2%), 8 (36.4%), and 19 (86.4%) of patients with DNSE infections, respectively. The mean duration of exposure to these agents before isolation of DNSE was 25.1, 27.9, and 44.1 days, respectively. Recent use of daptomycin before isolation of DNSE was documented in 13 (59.1%) patients with a mean duration of exposure 44.9 days (range, 10 to 90 days). Mean daptomycin daily dosage was 7.6 mg/kg with dosages including 6 mg/kg (n = 5, 22.7%), 8 mg/kg (n = 6, 27.3%), and 10 mg/kg (n =2, 9.1%), based on total body weight. Of note, 7 (31.8%) and 9 (40.9%) patients with DNSE infections had no prior exposure to vancomycin or daptomycin. Of 16 DNSE isolates that were tested for genetic relatedness there were 12 E. faecium, 3 E. faecalis and 1 E. gallinarum.  Four of 12 (33.3%) E. faecium isolates were genetically related and 2/12 were from patients with no prior daptomycin exposure. Two E. faecalis isolates from 2 patients with no prior exposure to daptomycin were 97.7% similar and these two isolates were also 98.5% related to a third DNS E. faecalis from a patient with 90 day of prior daptomycin exposure. 

Conclusion: 

Enterococcal resistance to daptomycin can emerge both with and without prior antimicrobial exposure, including to daptomycin. We identified one instance of possible horizontal transmission of DNSE strains. To our knowledge, this is the largest reported series of DSNE isolates.


Subject Category: A. Antimicrobial agents and Resistance

Theodoros Kelesidis, MD, Ronald Reagan UCLA Medical Center, Los Angeles, CA, Romney Humphries, Ph.D., Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA and David Pegues, MD, University of California, Los Angeles, Los Angeles, CA

Disclosures:

T. Kelesidis, None

R. Humphries, None

D. Pegues, None

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