What is the primary mechanism of action of beta-lactam antibiotics?

What is the primary mechanism of action of beta-lactam antibiotics?

• A. They inhibit bacterial cell wall synthesis by binding penicillin-binding proteins, preventing transpeptidation and causing cell lysis.
• B. They inhibit bacterial protein synthesis at the 30S ribosomal subunit.
• C. They inhibit DNA replication by targeting DNA gyrase.
• D. They disrupt the bacterial cell membrane to cause leakage.

Answer: (A)

Beta-lactam antibiotics kill by stopping cell wall synthesis. They bind penicillin-binding proteins, the enzymes that perform transpeptidation to cross-link peptidoglycan strands. When these enzymes are blocked, cross-linking can’t occur, the cell wall becomes weak, and the bacterium cannot withstand osmotic pressure as it grows, leading to cell lysis. This bactericidal action is most effective against actively dividing bacteria building their walls. The other descriptions correspond to different antibiotic classes—protein synthesis inhibitors at the 30S ribosomal subunit, inhibitors of DNA gyrase to block DNA replication, and agents that disrupt the cell membrane.

Beta-lactam antibiotics kill by stopping cell wall synthesis. They bind penicillin-binding proteins, the enzymes that perform transpeptidation to cross-link peptidoglycan strands. When these enzymes are blocked, cross-linking can’t occur, the cell wall becomes weak, and the bacterium cannot withstand osmotic pressure as it grows, leading to cell lysis. This bactericidal action is most effective against actively dividing bacteria building their walls. The other descriptions correspond to different antibiotic classes—protein synthesis inhibitors at the 30S ribosomal subunit, inhibitors of DNA gyrase to block DNA replication, and agents that disrupt the cell membrane.