title: Evaluation of mycobacteria growth indicator tubes for susceptibility testing of Mycobacterium tuberculosis to isoniazid and rifampin.
abstract: The reliability of mycobacteria growth indicator tubes (MGIT) for determining the susceptibility of Mycobacterium tuberculosis to isoniazid (0.1 microgram/ml) and rifampin (2.0 micrograms/ml) was evaluated by comparing MGIT results to those obtained by the radiometric BACTEC TB method. We tested 29 isolates, many selected for resistance. The turnaround times were 3-8 days (median 6) for MGIT and 4-10 days (median 6) for BACTEC. Isoniazid results by both methods agreed for all isolates tested: 20 resistant and nine susceptible. Rifampin results agreed for 28 isolates: 10 resistant and 18 susceptible. One isolate yielded discrepant results: resistant to rifampin by BACTEC, but susceptible by MGIT. This isolate was also rifampin-resistant by the traditional Method of Proportion and when tested by the MGIT method using 1.0 micrograms/ml of rifampin. The MGIT system is a nonradiometric alternative to the BACTEC for rapid susceptibility testing of M. tuberculosis to isoniazid and rifampin; however, additional testing is needed to determine the optimal concentration of rifampin.
authors.affiliation: Department of Pathology, University of Texas Medical Branch, Galveston 77555-0740, USA.
authors.forename: B S
authors.initials: BS
authors.lastname: Reisner
authors.forename: A M
authors.initials: AM
authors.lastname: Gatson
authors.forename: G L
authors.initials: GL
authors.lastname: Woods
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001431:Bacteriological Techniques / Q000295:instrumentation*; D003470:Culture Media; D004352:Drug Resistance, Microbial; D005069:Evaluation Studies as Topic; D007538:Isoniazid / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000254:growth & development; D012293:Rifampin / Q000494:pharmacology*
chemical_list: D000995:Antitubercular Agents; D003470:Culture Media; D007538:Isoniazid; D012293:Rifampin