Diluent for trimethoprim in antibiotic disc for sensitivity testing is
**Core Concept**
Trimethoprim is a bacteriostatic antibiotic that inhibits dihydrofolate reductase (DHFR), an enzyme crucial for bacterial DNA synthesis. In sensitivity testing, trimethoprim is combined with sulfamethoxazole (co-trimoxazole) to evaluate its effectiveness against various bacterial pathogens.
**Why the Correct Answer is Right**
The correct answer is related to the preparation of antibiotic discs for sensitivity testing. Trimethoprim is often used in combination with sulfamethoxazole, and the standard diluent for these discs is usually Mueller-Hinton agar. However, when used alone, trimethoprim is typically dissolved in distilled water or saline. Since the question only asks for the diluent of trimethoprim, the focus is on the correct solvent.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a suitable diluent for trimethoprim.
**Option B:** This option is incorrect because it is not a standard diluent for antibiotic discs.
**Option C:** This option is incorrect because it is not a suitable solvent for trimethoprim.
**Clinical Pearl / High-Yield Fact**
When preparing antibiotic discs, it is essential to use the correct diluent to ensure accurate results. The choice of diluent can affect the antibiotic's potency and the overall outcome of the sensitivity test.
**Correct Answer: B. Distilled water.**