🦠microbiology review

Penicillin G

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

Definition

Penicillin G is a narrow-spectrum antibiotic effective primarily against Gram-positive bacteria. It is often used to treat serious infections like syphilis, endocarditis, and certain types of bacterial meningitis.

5 Must Know Facts For Your Next Test

  1. Penicillin G is administered intravenously or intramuscularly due to its instability in the acidic environment of the stomach.
  2. It works by inhibiting the synthesis of bacterial cell walls, leading to cell lysis and death.
  3. Penicillin G remains one of the first-line treatments for infections caused by Streptococcus species, including Streptococcus pyogenes, which can cause urogenital and circulatory system infections.
  4. Resistance to Penicillin G can occur through the production of beta-lactamase enzymes by bacteria.
  5. Side effects may include allergic reactions, ranging from rash to anaphylaxis.

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