1203. In Vitro Activity of Newer Antimicrobials and Relevant Comparators Versus 349 Stenotrophomonas maltophilia Clinical Isolates Obtained from Patients in Canadian Hospitals (CANWARD, 2011-2016)
Session: Poster Abstract Session: Expanded Spectrum - New Antimicrobial Susceptibility Testing
Friday, October 6, 2017
Room: Poster Hall CD
Posters
  • Walkty Stenotrophomonas IDWeek 2017.pdf (387.4 kB)
  • Background:  Stenotrophomonas maltophilia is a non-fermentative gram-negative bacillus that has emerged as an important opportunistic pathogen among hospitalized, debilitated patients.  Treatment options for infections caused by this organism are limited because it is intrinsically resistant to antimicrobials from multiple different classes.    The purpose of this study was to evaluate the in vitro activity of several newer antimicrobial agents (ceftazidime-avibactam [CZA], ceftolozane-tazobactam [C/T], moxifloxacin [MXF], tigecycline [TGC]) and relevant comparators [e.g., trimethoprim-sulfamethoxazole [TMP-SMX]) against a large collection of S. maltophilia clinical isolates obtained as part of an ongoing national surveillance study (CANWARD, 2011-2016).

    Methods:  From January 2011 to December 2016, inclusive, 12 to 15 sentinel hospitals across Canada submitted clinical isolates from patients attending ERs, medical and surgical wards, hospital clinics, and ICUs (CANWARD).  Each center was asked to annually submit clinical isolates (consecutive, one per patient/infection site) from blood (100), respiratory (100), urine (25), and wound (25) infections.  Susceptibility testing was performed using broth microdilution as described by CLSI.  MICs were interpreted using CLSI breakpoints, where available. 

    Results:  349 S. maltophilia clinical isolates were obtained as a part of CANWARD (86% from a respiratory source).  The susceptibility profile of these isolates is presented below.

    Antimicrobial

    MIC50

    (µg/mL)

    MIC90

    (µg/mL)

    Susceptibility Breakpoint

    (µg/mL)

    % Susceptible

    <>Ceftazidime

    >32

    >32

    ≤8

    22.1

    CZA

    >16

    >16

    ≤8

    26.9

    C/T

    32

    >64

    Not defined

    No data

    Ciprofloxacin

    2

    16

    Not defined

    No data

    MXF

    0.5

    4

    Not defined

    No data

    Doxycycline

    2

    4

    Not defined

    No data

    TGC

    1

    4

    Not defined

    No data

    Colistin

    4

    >16

    Not defined

    No data

    TMP-SMX

    0.5

    2

    ≤2

    98.2

    CZA and C/T demonstrated poor in vitro activity versus the isolates.  The in vitro activity of MXF was approximately 4 fold more potent than ciprofloxacin.  TGC was marginally more active in vitro than doxycycline.

    Conclusion:  TMP-SMX continues to demonstrate excellent in-vitro activity against S. maltophilia clinical isolates.  MXF and TGC may also prove useful in the treatment of infections caused by this pathogen. 

    Andrew Walkty, MD1,2, Melanie Baxter, MSc3, Heather J. Adam, PhD1,2, Philippe Lagace-Wiens, MD3,4, James Karlowsky, PhD1,2 and George Zhanel, PhD3, (1)Diagnostic Services Manitoba, Winnipeg, MB, Canada, (2)Medical Microbiology, University of Manitoba, Winnipeg, MB, Canada, (3)Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, MB, Canada, (4)Shared Health, Winnipeg, MB, Canada

    Disclosures:

    A. Walkty, None

    M. Baxter, None

    H. J. Adam, None

    P. Lagace-Wiens, None

    J. Karlowsky, None

    G. Zhanel, Achaogen: Research relationship , Research support
    Astellas: Research relationship , Research support
    Merck Canada: Research relationship , Research support
    Merck USA: Research relationship , Research support
    Paratek Pharma: Research relationship , Research support
    Pharmascience: Research relationship , Research support
    Sunovion: Research relationship , Research support
    Tetraphase: Research relationship , Research support
    The Medicines Co.: Research relationship , Research support
    Zoetis: Research relationship , Research support

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