Penicillins Mechanism of Action Quiz

Adverse Effects of Penicillins

• The primary adverse effect of penicillins is allergic reaction.

Mechanism of Action

• Penicillins weaken the bacterial cell wall by inhibiting the synthesis of peptidoglycan, a critical component of the bacterial cell wall.
• They do this by binding to the enzyme DD-transpeptidase, which is necessary for peptidoglycan synthesis.

Structural Features

• Penicillins are often referred to as beta-lactam antibiotics due to a structural feature, the beta-lactam ring.

Mode of Action

• The mode of action of penicillins against bacteria is the inhibition of bacterial cell wall synthesis.

Bacterial Resistance

• Three primary factors determine bacterial resistance to penicillins:
  • The genetic makeup of the bacterial species
  • The ability of the bacterium to produce beta-lactamases
  • The permeability of the bacterial outer membrane to penicillins
• Beta-lactamases are enzymes that break down penicillins, rendering them ineffective.
• The genes that code for beta-lactamases are typically located on plasmids, which are small, self-replicating circular DNA molecules.

Methicillin-Resistant Staphylococcus Aureus (MRSA)

• A significant characteristic of MRSA is its high level of resistance to penicillins and other beta-lactam antibiotics.
• Methicillin was introduced to combat penicillin resistance in Staphylococcus aureus.
• Methicillin is a semi-synthetic penicillin that was developed to combat penicillin-resistant Staphylococcus aureus.

Penicillin Structure

• All penicillins are derived from a common nucleus, 6-aminopenicillanic acid (6-APA).