255. In vitro Activity of Dalbavancin against Neisseria gonorrhoeae and Development of a Broth Microdilution Method 
Session: Poster Abstract Session: Diagnostic Microbiology; Antimicrobial Sensitivities
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
  • IDSA GC Dalbavancin Poster 4Sept2013.pdf (1.4 MB)
  • Background:

    As antimicrobial resistance rates increase among Neisseria gonorrhoeae, it is important to investigate other treatment alternatives and also to provide a methodology of testing that will be more adaptable to a routine clinical laboratory.     This study was performed to determine the in vitro activity of dalbavancin against a challenge set of Neisseria gonorrhoeae and to initiate development of a broth microdilution method for testing of Neisseria gonorrhoeae.


    Dalbavancin, ceftriaxone and ciprofloxacin BMD and AD MIC results were obtained for a set of 31 N. gonorrhoeae (11 susceptible strains including QC strain ATCC 49226 and 20 resistant strains) and QC S. aureus ATCC 29213.  The CLSI recommended MIC procedure for testing Neisseria gonorrhoeae is an agar dilution (AD) methodology.  Based on prior studies, which have shown significantly higher dalbavancin MICs with AD, a broth microdilution method (BMD) with addition of 0.002% polysorbate 80 (P80) is suggested for testing Neisseria gonorrheae against dalbavancin.    A modified GC broth (substitution of glucose instead of starch) + 0.002% P80 was used for testing of dalbavancin and GC broth was used for the two comparator agents.   All MIC plates were incubated in CO2 and results were read after 48 hours.


    Dalbavancin BMD MIC results were 0.12-1 µg/mL compared to AD MIC results of 1-4 µg/mL.  There were 7 strains that did not grow in the modified GC broth.  All strains were susceptible to ceftriaxone (<0.06 µg/mL).  A total of 9 strains were resistant to ciprofloxacin (>0.5 µg/mL) and remaining 12 strains were susceptible (≤0.06 µg/mL).  The dalbavancin BMD MIC for N. gonorrhoeae ATCC 49226 was 0.5-1 µg/mL and for S. aureus ATCC 29213 was 0.06-0.12 µg/mL.  The dalbavancin MIC distribution (number at each MIC) for 24 strains by MIC method is shown in the table.


    MIC (µg/mL)






















    The in vitro activity of dalbavancin against this challenge set of Neisseria gonorrhoeae by BMD is an indication of possible in vivo activity that will require further investigation.  As a result of lack of growth with some strains in the modified broth, additional development is necessary using the broth methodology for dalbavancin.

    Laura Koeth and Jeanna Difranco-Fisher, Laboratory Specialists, Inc., Westlake, OH


    L. Koeth, Durata Therapeutics: Research Contractor, Research support

    J. Difranco-Fisher, Durata Therapeutics: Research Contractor, Research support

    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.