Drug Susceptibility Testing
Drug susceptibility testing is a difficult procedure to standardize, and proficiency in performing these tests requires an understanding of many elements, including the
- Origin of drug resistance and the criteria for resistance
- Potency and stability of drugs during laboratory manipulation
- Antimycobacterial activity of drugs when incorporated into different media
- Reading, interpretation, and reporting of results
The LB uses an indirect proportion method for testing M. tuberculosis complex mycobacteria to 12 drugs at 35C on Middlebrook 7H10 agar. The test requires 1 month to complete. Growth on the control medium is compared to the growth on the drug-containing medium to determine susceptibility or resistance. When performed properly, this method allows a quantitation of the proportion of mutants resistant to a drug and can detect the 1% proportion of drug- resistant mutants above which therapeutic failure is likely.
M. tuberculosis complex are tested by this method with the following drugs:
- Para-aminosalicylic acid (PAS)
Pyrazinamide is tested by the MGIT 960 method.
Additionally, bedaquiline testing is available upon requestpdf icon [PDF 108 KB]