Quality control ranges for testing broth microdilution susceptibility of Flavobacterium columnare and F. psychrophilum to nine antimicrobials

Charles M. Gieseker, Tamara D. Mayer, Tina C. Crosby, Jeremy Carson, Inger Dalsgaard, Ahmed M. Darwish, Patricia S. Gaunt, Dana X. Gao, Hui-Min Hsu, Tsang L. Lin, J. Lindsay Oaks, Melissa Pyecroft, Charlene Teitzel, Temdoung Somsiri, Ching C. Wu

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    A multi-laboratory broth microdilution method trial was performed to standardize the specialized test conditions required for the fish pathogens Flavobacterium columnare and F. psychrophilum. Nine laboratories tested the quality control (QC) strains Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 against 10 antimicrobials (ampicillin, enrofloxacin, erythromycin, florfenicol, flumequine, gentamicin, ormetoprim/sulfadimethoxine, oxolinic acid, oxytetracycline, and trimethoprim/sulfamethoxazole) in diluted (4 g l−1) cation-adjusted Mueller-Hinton broth incubated at 28 and 18°C for 44–48 and 92–96 h, respectively. QC ranges were set for 9 of the 10 antimicrobials. Most of the minimal inhibitory concentration (MIC) distributions (16 of 18, 9 drugs at both temperatures) for A. salmonicida ATCC 33658 were centered on a single median MIC ± 1 two-fold drug dilution resulting in a QC range that spanned 3 dilutions. More of the E. coli ATCC 25922 MIC distributions (7 of 16) were centered between 2 MIC dilutions requiring a QC range that spanned 4 dilutions. A QC range could not be determined for E. coli ATCC 25922 against 2 antimicrobials at the low temperature. These data and their associated QC ranges have been approved by the Clinical and Laboratory Standards Institute (CLSI), and will be included in the next edition of the CLSI M49-A Guideline. This method represents the first standardized reference method for testing fish pathogenic Flavobacterium spp.
    Original languageEnglish
    JournalDiseases of Aquatic Organisms
    Volume101
    Issue number3
    Pages (from-to)207-215
    ISSN0177-5103
    DOIs
    Publication statusPublished - 2012

    Keywords

    • Standard methods
    • Antimicrobial susceptibility testing
    • Fish
    • Flavobacteria

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