Quinuspristine/dalfopristine act by –
**Core Concept**
The question tests the student's knowledge of the mechanism of action of quinupristin/dalfopristin, a **streptogramin** antibiotic combination. This combination is used to treat various bacterial infections, particularly those caused by **Gram-positive** organisms.
**Why the Correct Answer is Right**
Quinupristin/dalfopristin acts by inhibiting **protein synthesis** in bacteria. Quinupristin is a **streptogramin B** component, which binds to the **50S ribosomal subunit** and prevents the extension of the peptide chain. Dalfopristin is a **streptogramin A** component, which binds to the **50S ribosomal subunit** as well and causes the termination of protein synthesis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because quinupristin/dalfopristin does not act by inhibiting **cell wall synthesis**.
**Option B:** This option is incorrect because quinupristin/dalfopristin does not act by inhibiting **DNA synthesis**.
**Option C:** This option is incorrect because quinupristin/dalfopristin does not act by inhibiting **cell membrane function**.
**Clinical Pearl / High-Yield Fact**
Quinupristin/dalfopristin is effective against **vancomycin-resistant Enterococci**, making it a valuable option for treating infections caused by these organisms.
**Correct Answer:** D. Inhibiting protein synthesis.