🦠microbiology review

Penicillins

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Penicillins are a group of antibiotics derived from Penicillium fungi, effective against many Gram-positive bacteria. They inhibit bacterial cell wall synthesis, leading to cell lysis and death.

5 Must Know Facts For Your Next Test

  1. Penicillins target the bacterial enzyme transpeptidase, essential for cell wall synthesis.
  2. They are primarily effective against Gram-positive bacteria but have limited efficacy against Gram-negative bacteria.
  3. Commonly used penicillins include penicillin G, penicillin V, amoxicillin, and ampicillin.
  4. Bacterial resistance to penicillin can occur through the production of beta-lactamase enzymes that break down the antibiotic.
  5. Penicillins can cause allergic reactions in some individuals, ranging from mild rashes to severe anaphylaxis.

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