Commonly used phenotypic methods for AST of the M. tuberculosis complex in the United States

Growth-based methodFormatComments
Indirect agar proportion methodCritical concn; solid media (Middlebrook 7H10 or 7H11 agar); turnaround time of ∼1 mo from setup dateCriterion “gold standard”; complex method; pyrazinamide testing not available; long turnaround time; laboratory-developed test; not commercially available
Bactec MGIT320 or MGIT960 mycobacterial detection system (Becton-Dickinson)Critical concn; liquid media (MGIT); turnaround time of 4–13 days from setup dateReported issues with ethambutol critical concn and false pyrazinamide resistancea; FDA cleared for first-line drugs
VersaTREK (ThermoFisher Scientific)Critical concn; growth matrix liquid/sponge; turnaround time of 4–13 days from setup dateFDA cleared for first-line drugs
Sensititre (ThermoFisher Scientific)MIC; liquid media; turnaround time of 14–21 days from setup datePZA testing not available; no MIC interpretive criteria; research-use-only test
  • a See references 344 and 345.