Which of the following best describes the mode of action of aminoglycosides?

• A. They disrupt cell wall synthesis by inhibiting transpeptidase enzymes.
• B. They inhibit protein synthesis by binding to the 30S ribosomal subunit.
• C. They interfere with DNA gyrase, preventing DNA replication.
• D. They inhibit folic acid synthesis by blocking dihydropteroate synthase.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the general mechanism of aminoglycosides. Aminoglycosides are a class of antibiotics known to target bacterial protein synthesis.
2. Step 2: Recall that bacterial ribosomes consist of two subunits: the 30S (small) and 50S (large) subunits. Different antibiotics target different subunits to inhibit protein synthesis.
3. Step 3: Recognize that aminoglycosides specifically bind to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting the initiation of protein synthesis.
4. Step 4: Compare this mode of action with other antibiotic mechanisms: disruption of cell wall synthesis (e.g., beta-lactams), inhibition of DNA gyrase (e.g., fluoroquinolones), and inhibition of folic acid synthesis (e.g., sulfonamides).
5. Step 5: Conclude that the best description of aminoglycosides' mode of action is their inhibition of protein synthesis by binding to the 30S ribosomal subunit.