Beginning Monday, June 29, 2026, minimum inhibitory concentration (MIC) testing for a panel of anti-tuberculosis drugs will be implemented as part of CDC’s Molecular Detection of Drug Resistance (MDDR) service (test order CDC-10186). The addition of MIC testing will enhance phenotypic testing capabilities by providing MIC values for the following drugs using broth microdilution: rifampin, isoniazid, ethambutol, levofloxacin, moxifloxacin, amikacin, linezolid, clofazimine, and bedaquiline. In addition, MIC testing for pretomanid will also be performed using the BD MGIT system.
MIC testing will be available only for samples with known rifampin resistance or when there is a compelling clinical need. Pre-approval is required and must be requested using the revised MDDR Request Form. To request MIC testing, complete the form, including the newly added Section 4, and email the completed form to TBLab@cdc.gov or include as an attachment to the request submitted via CDC’s Specimen Test Order and Reporting (CSTOR) web portal.
In addition, samples submitted to the MDDR service that are determined to be rifampin resistant in our laboratory will undergo reflex MIC testing. All samples submitted for MDDR testing will continue to receive molecular testing by our targeted next generation sequencing (tNGS) assay and phenotypic drug susceptibility testing by agar proportion. For samples approved for MIC testing, reports will include molecular results, agar proportion results, and MIC values for the drugs included in the CDC MIC testing panel. Clinical consultation is available upon request.
Under this service, all submitted samples will undergo molecular testing by tNGS as well as phenotypic drug susceptibility testing by agar proportion. As described above, MIC testing may also be performed following pre-approval or through reflex testing when rifampin resistance is detected by tNGS.
Additional information about the tNGS assay, MDDR service, specimen submission requirements, and use of the MDDR Request Form can be found in the MDDR User’s Guide. This guide will be updated in the future to include reference to MIC testing. For questions, contact TBLab@cdc.gov .
