title: Safe determination of susceptibility of Mycobacterium tuberculosis to antimycobacterial agents by flow cytometry.
abstract: We showed previously that susceptibility testing for Mycobacterium tuberculosis labeled with fluorescein diacetate could be accomplished rapidly by using flow cytometry. However, safety was a major concern because mycobacteria were not killed prior to flow cytometric analysis. In this study, we developed a biologically safe flow cytometric susceptibility test that depends on detection and enumeration of actively growing M. tuberculosis organisms in drug-free and antimycobacterial agent-containing medium. The susceptibilities of 17 clinical isolates of M. tuberculosis to ethambutol, isoniazid, and rifampin were tested by the agar proportion and flow cytometric methods. Subsequently, all flow cytometric susceptibility test samples were inactivated by exposure to paraformaldehyde before analysis with a flow cytometer. Agreement between the results from the two methods was 98%. In addition, the flow cytometric results were available 72 h after the initiation of testing. The flow cytometric susceptibility assay is safe, simple to perform, and more rapid than conventional test methods, such as the BACTEC system and the proportion method.
authors.affiliation: Wisconsin State Laboratory of Hygiene, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: A V
authors.initials: AV
authors.lastname: Moore
authors.forename: S M
authors.initials: SM
authors.lastname: Kirk
authors.forename: S M
authors.initials: SM
authors.lastname: Callister
authors.forename: G H
authors.initials: GH
authors.lastname: Mazurek
authors.forename: R F
authors.initials: RF
authors.lastname: Schell
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D005434:Flow Cytometry / Q000379:methods; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000592:standards; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D011786:Quality Control; D012449:Safety; D013997:Time Factors