Antimicrobial Drugs and Antibiotics Overview

Antimicrobial Drugs

• Antimicrobial drugs treat microbial infections.

Antibiotics

• Antibiotics kill or inhibit bacterial growth, treating bacterial infections.
• They fight pathogens.
• These drugs interfere with cell wall formation.
• Many are derived from bacteria or fungi; others are synthetically produced.

History of Antibiotics

• The first antibiotic's discovery was accidental.
• In 1928, Alexander Fleming noticed a clear area of no bacterial growth where a fungus contaminated a culture plate.

Zone of Inhibition

• If an antibiotic stops bacteria growth or kills them, a zone of no bacterial growth forms around the antibiotic.
• Factors affecting zone size:
  • Drug diffusion rate
  • Drug concentration
  • Type of microorganism
  • Type of drug

Narrow and Broad-Spectrum Antibiotics

• Narrow-spectrum: affect a specific group of microbes, like gram-positive bacteria (e.g., Erythromycin, Clarithromycin, Clindamycin).
  • Advantage: less likely to harm normal body microorganisms.
  • Use: only when the causative organism is identified.
• Broad-spectrum: affect a wide range of microbes (e.g., Azithromycin, Amoxicillin, Vancomycin, Levofloxacin, Streptomycin, Tetracycline, Chloramphenicol).
  • Disadvantage: Increased risk of harming normal body microorganisms, leading to superinfections or drug resistance.

Antibiotic Targets

• Bacterial cell wall
• Bacterial plasma membrane
• Bacterial protein synthesis
• Bacterial nucleic acids (DNA/RNA)
• Bacterial metabolism

Inhibitors of Cell Wall Synthesis

• Penicillins, containing a β-lactam ring, are effective against gram-positive bacteria produced by Penicillium.

Inhibitors of Protein Synthesis

• Aminoglycosides, tetracyclines, chloramphenicol, and macrolides inhibit protein synthesis at 70S ribosomes.

Inhibitors of Nucleic Acid Synthesis

• Rifamycin inhibits mRNA synthesis and is used to treat tuberculosis (Mycobacterium tuberculosis).
• Quinolones and fluoroquinolones inhibit DNA gyrase for urinary tract infections.

Antibiotic Resistance

• Resistance can be inherent (present in some bacteria naturally) or acquired (through gene transfer/spontaneous mutations).

Mechanisms of Antibiotic Resistance

• Enzyme production: Enzymes like beta-lactamases modify antibiotics to deactivate them. Enzymes often result in inactivation.
• Aminoglycoside modifying enzymes.
• Chloramphenicol acetyl transferase.
• Mutations in bacterial structures (e.g., penicillin-binding proteins [PBPs])
• Efflux pumps expelling antibiotics from the bacteria

Allergy Testing

• Used to identify substances causing allergic reactions.
  • Skin prick test
  • Patch test

Antifungal Drugs

• Treat and prevent fungal infections (mycoses).
• Classes:
  • Polyenes
  • Imidazoles
  • Triazoles
  • Allylamines
  • Inhibitors

Antiretroviral Drugs

• Treat viral infections, specifically targeting different aspects of viral life processes.
• Classes:
  • Nucleos(t)ide Reverse Transcriptase Inhibitors (NRTIs)
  • Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
  • Protease Inhibitors
  • Entry Inhibitors
  • Integrase Inhibitors

Antiprotozoan and Antihelminthic Drugs

• Treat parasitic infections
• Examples: Chloroquine, quinacrine, metronidazole, niclosamide.
• Mechanisms can include stopping DNA synthesis or parasite growth.

This quiz covers the essentials of antimicrobial drugs, focusing specifically on antibiotics. It examines their mechanisms of action, the history of their discovery, and concepts like the zone of inhibition and spectrum of activity. Test your knowledge on how these important compounds combat microbial infections.