Gene responsible for INH resistance is ?
**Core Concept**
The development of resistance to isoniazid (INH), a first-line antitubercular medication, is a significant concern in tuberculosis (TB) management. This resistance is primarily attributed to genetic mutations in the bacterial genome, which affect the functioning of the enzyme responsible for INH's mechanism of action.
**Why the Correct Answer is Right**
Isoniazid exerts its antibacterial effect by inhibiting the synthesis of mycolic acid, a crucial component of the Mycobacterium tuberculosis cell wall. The primary target of INH is the enzyme enoyl-acyl carrier protein reductase (InhA). Mutations in the inhA gene or in the promoter region of the inhA gene, known as inhA promoter region, can lead to INH resistance. The correct gene responsible for INH resistance is the inhA gene, which encodes the InhA enzyme.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not directly relate to the mechanism of INH action or resistance.
**Option B:** This option is incorrect as it refers to a different enzyme, katG, which is involved in the activation of INH, but not directly responsible for INH resistance.
**Option C:** This option is incorrect as it refers to a gene that is not directly involved in INH resistance.
**Clinical Pearl / High-Yield Fact**
When managing TB patients, it is essential to consider the possibility of INH resistance, especially in cases where treatment failure occurs despite adequate dosing and adherence. Regular monitoring of drug susceptibility patterns and the use of molecular diagnostic techniques can help identify resistant strains and guide appropriate treatment modifications.
**Correct Answer:** C.