title: Re-evaluation of the critical concentration for ethambutol antimicrobial sensitivity testing on the MGIT 960.
abstract: The critical concentration (CC) for ethambutol testing on the Bactec MGIT 960 M. tuberculosis susceptibility testing has been questioned in recent publications. In this study, we correlate susceptibility results from the Bactec 460, MGIT 960 and embB gene sequencing to determine if the Bactec MGIT 960 adequately detects ethambutol resistance. We discovered discrepancies between the methods that highlight a need to re-evaluate ethambutol susceptibility testing recommendations, namely by considering lowering currently recommended CC on the MGIT 960. Further studies on the clinical significance of low-level ethambutol resistance are also required.
authors.affiliation: National Reference Centre for Mycobacteriology, National Microbiology Laboratory Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Sara
authors.initials: S
authors.lastname: Christianson
authors.affiliation: Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Dylan
authors.initials: D
authors.lastname: Voth
authors.affiliation: National Reference Centre for Mycobacteriology, National Microbiology Laboratory Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Joyce
authors.initials: J
authors.lastname: Wolfe
authors.affiliation: National Reference Centre for Mycobacteriology, National Microbiology Laboratory Public Health Agency of Canada, Winnipeg, Manitoba, Canada; Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Meenu K
authors.initials: MK
authors.lastname: Sharma
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D004977:Ethambutol / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects*
chemical_list: D000995:Antitubercular Agents; D004977:Ethambutol