Lecture Notes: Differentiating Aminoglycosides and Macrolides

Introduction

• Discussion on how to differentiate between aminoglycosides and macrolides.
• Both groups often end with the suffix -mycin.

Aminoglycosides

• First discovered: Streptomycin
  • Used to treat tuberculosis.
• Examples:
  • Streptomycin, Tobramycin, Kanamycin, Neomycin
  • Typically used for lung infections in cystic fibrosis patients.
• Origin: Derived from the Streptomyces genus (a type of actinomycetes).
• Exceptions: Some aminoglycosides end with -micin (Gentamicin, Netilmicin, Sisomicin, Plazomicin) derived from Micromonospora genus.

Macrolides

• First discovered: Erythromycin
• Examples:
  • Erythromycin, Clarithromycin, Azithromycin, Roxithromycin
  • Identified by the -thromycin suffix.
• Origin: Derived from Saccharopolyspora erythraea.
• Common Use: Erythromycin is still widely used.

Differentiating Factors

• Suffix Identification:
  • Aminoglycosides: -mycin
  • Macrolides: -thromycin
• Origin:
  • Aminoglycosides: Actinomycetes (Streptomyces for -mycin, Micromonospora for -micin)
  • Macrolides: Saccharopolyspora

Importance of Actinomycetes

• Actinomycetes are a significant source of antibiotics, producing 70-80% of natural antibiotics today.

Antibiotics Mechanism

• Aminoglycosides: Inhibit protein synthesis on the 30S ribosomal subunit.
  • Exceptionally bactericidal.
• Macrolides: Inhibit protein synthesis on the 50S ribosomal subunit.
  • Typically bacteriostatic.

Erythromycin vs. Clarithromycin vs. Azithromycin

• Erythromycin:
  • Less stable in gastric acid, requires frequent dosing (6-8 hourly).
  • More gastrointestinal and cardiac side effects.
  • Significant drug-drug interactions.
• Clarithromycin & Azithromycin:
  • More stable, better absorption, longer half-lives, leading to less frequent dosing (12-hourly for Clarithromycin, daily for Azithromycin).
  • Broader spectrum, less side effects, minimal drug-drug interactions.

Conclusion

• Recognize macrolides by their -thromycin suffix.
• Aminoglycosides and macrolides both inhibit protein synthesis but differ significantly in their bactericidal and bacteriostatic actions respectively.