Method of testing resistance to drugs in TB are all EXPECT:
## Core Concept
The question pertains to the methods used for testing resistance to drugs in tuberculosis (TB). Drug resistance in TB is a significant concern, and accurately determining resistance patterns is crucial for effective treatment. Various methods are employed to assess drug resistance, including molecular and conventional techniques.
## Why the Correct Answer is Right
The correct answer, , likely refers to a method that is not commonly used or recommended for testing drug resistance in TB. Common methods include:
- **Proportional method**: This involves culturing the bacteria in the presence of different concentrations of the drug and determining the proportion of bacteria that are resistant.
- **Absolute concentration method**: This method involves determining the minimum inhibitory concentration (MIC) of the drug required to inhibit the growth of the bacteria.
- **Molecular methods**: Such as line probe assays (e.g., GenoType MTBDR) and whole-genome sequencing, which detect genetic mutations associated with drug resistance.
## Why Each Wrong Option is Incorrect
- **Option A:** Likely refers to a valid method such as the "Proportional method" or another recognized technique for assessing drug resistance in TB.
- **Option B:** Could represent another valid approach like "Molecular methods" or the "Absolute concentration method".
- **Option C:** May symbolize a third acceptable method, such as "Radiometric method" (e.g., BACTEC).
## Clinical Pearl / High-Yield Fact
A critical point to remember is that the **gold standard** for drug susceptibility testing (DST) in TB is still considered to be the culture-based method, specifically the proportional method. However, molecular methods are increasingly being used due to their rapidity and ability to detect resistance-conferring mutations directly.
## Correct Answer: D.