title: Comparison of Clostridium difficile minimum inhibitory concentrations obtained using agar dilution vs broth microdilution methods.
abstract: Due to increasing antibiotic resistance among anaerobic bacteria, routine antimicrobial susceptibility testing is recommended by the Clinical and Laboratory Standards Institute (CLSI). This study compared the minimum inhibitory concentrations (MICs) from 920 Clostridium difficile isolates tested against seven antimicrobial agents using the two current CLSI reference methodologies, agar dilution method, vs broth microdilution method. A subset of isolate testing was performed independently by two laboratories to evaluate reproducibility. A negative bias was noted for MICs generated from broth microdilution compared to agar dilution and the reproducibility was variable and drug dependent. Therefore, broth microdilution is not recommended as an alternative to agar dilution for C. difficile antimicrobial susceptibility testing.
authors.affiliation: Beckman Coulter Diagnostics, Inc., West Sacramento, CA, United States.
authors.forename: Christine J
authors.initials: CJ
authors.lastname: Hastey
authors.affiliation: ACM Global Laboratories, Rochester, NY, United States.
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Dale
authors.affiliation: ACM Global Laboratories, Rochester, NY, United States.
authors.forename: Julia
authors.initials: J
authors.lastname: Nary
authors.affiliation: R.M. Alden Research Laboratory, Culver City, CA, United States.
authors.forename: Diane
authors.initials: D
authors.lastname: Citron
authors.affiliation: Beckman Coulter Diagnostics, Inc., West Sacramento, CA, United States.
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Law
authors.affiliation: Beckman Coulter Diagnostics, Inc., West Sacramento, CA, United States. Electronic address: decarpenter@beckman.com.
authors.forename: Darcie E
authors.initials: DE
authors.lastname: Roe-Carpenter
authors.affiliation: Merck Sharp & Dohme Corp, Kenilworth, NJ, United States.
authors.forename: Laurent
authors.initials: L
authors.lastname: Chesnel
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016360:Clostridioides difficile / Q000187:drug effects* / Q000302:isolation & purification; D003470:Culture Media / Q000737:chemistry*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media
keywords: C. difficile; MIC determination; Susceptibility testing