Which class of antibiotics inhibits bacterial cell wall synthesis by binding penicillin-binding proteins?

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Multiple Choice

Which class of antibiotics inhibits bacterial cell wall synthesis by binding penicillin-binding proteins?

Beta-lactam antibiotics inhibit bacterial cell wall synthesis by binding penicillin-binding proteins, the enzymes that cross-link the peptidoglycan mesh essential for cell wall strength. They resemble the normal substrate of these enzymes and acylate the active-site serine, inactivating the transpeptidase activity needed to form the cross-links. Without proper cross-linking, the cell wall becomes weak, and growing bacteria cannot maintain integrity, leading to cell lysis from osmotic pressure. This mechanism underlies the bactericidal nature of these drugs and explains their effectiveness against actively dividing bacteria. This class includes penicillins, cephalosporins, carbapenems, and monobactams. Resistance can occur via beta-lactamases that destroy the antibiotic or by alterations in PBPs that reduce binding affinity, as seen with MRSA. Clinically, beta-lactamase inhibitors can be used to extend activity against beta-lactamase-producing organisms. Other antibiotic classes act on different targets: macrolides bind the 50S ribosome to inhibit protein synthesis; tetracyclines block the 30S ribosome to prevent tRNA binding; fluoroquinolones inhibit DNA gyrase and topoisomerase IV to disrupt DNA replication.

Beta-lactam antibiotics inhibit bacterial cell wall synthesis by binding penicillin-binding proteins, the enzymes that cross-link the peptidoglycan mesh essential for cell wall strength. They resemble the normal substrate of these enzymes and acylate the active-site serine, inactivating the transpeptidase activity needed to form the cross-links. Without proper cross-linking, the cell wall becomes weak, and growing bacteria cannot maintain integrity, leading to cell lysis from osmotic pressure. This mechanism underlies the bactericidal nature of these drugs and explains their effectiveness against actively dividing bacteria.

This class includes penicillins, cephalosporins, carbapenems, and monobactams. Resistance can occur via beta-lactamases that destroy the antibiotic or by alterations in PBPs that reduce binding affinity, as seen with MRSA. Clinically, beta-lactamase inhibitors can be used to extend activity against beta-lactamase-producing organisms.

Other antibiotic classes act on different targets: macrolides bind the 50S ribosome to inhibit protein synthesis; tetracyclines block the 30S ribosome to prevent tRNA binding; fluoroquinolones inhibit DNA gyrase and topoisomerase IV to disrupt DNA replication.

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