Antimicrobial Drugs and Antibiotics Overview

Antimicrobial Drugs

• Antimicrobial drugs treat microbial infections.
• Antibiotics kill or inhibit bacterial growth, used to treat bacterial infections.

Antibiotics

• Fight pathogens.
• Interfere with cell wall formation.
• Many are obtained from bacteria or fungi.
• Some are synthetically produced.

History of Antibiotics

• The first antibiotic's discovery was accidental.
• In 1928, Alexander Fleming, a Scottish biologist, accidentally contaminated a petri dish with fungus.
• He observed a clear area of no bacterial growth where the fungus had contaminated the dish.

Zone of Inhibition

• If antibiotics stop bacteria from growing or killing them, a zone of no growth (zone of inhibition) appears around the antibiotic disc on a Petri dish.
• Factors affecting zone size include:
  • Drug diffusion rate in the agar.
  • Drug concentration in the disk.
  • Type of microorganism.
  • Type of drug.

Narrow and Broad-spectrum Antibiotics

• Narrow-spectrum antibiotics target specific microbes (e.g., gram-positive cells). Examples include erythromycin, clarithromycin, clindamycin.
• Advantages: Less likely to harm normal body microorganisms, reducing the risk of superinfections
• Narrow-spectrum antibiotics are used only when the cause of the infection is known.
• Broad-spectrum antibiotics affect many different microbes. Examples include azithromycin, amoxicillin, vancomycin, levofloxacin, streptomycin, tetracycline, chloramphenicol.
• Disadvantages: Can harm beneficial microorganisms in the body, increasing the risk of superinfections and drug resistance.
• Children taking broad-spectrum antibiotics in their first year are at higher risk for childhood asthma.
• Broad-spectrum antibiotics can cause drug resistance.

Antibiotic Targets

• Bacterial cell wall
• Bacterial plasma membrane
• Bacterial protein synthesis
• Bacterial nucleic acids
• Bacteria metabolism

Inhibitors of Cell Wall Synthesis

• Penicillins contain a beta-lactam ring.
• Natural penicillins (produced by Penicillium) are effective against gram-positive bacteria.

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 are used to treat tuberculosis.
• Quinolones and fluoroquinolones inhibit DNA gyrase to treat urinary tract infections.

How Resistance Spreads

• Antibiotic resistance can be inherent or acquired.
• Inherent resistance: Some bacteria are naturally resistant due to physiological characteristics.
• Acquired resistance: Other bacteria acquire resistance through resistance gene transfer or spontaneous chromosomal mutations.

Mechanisms of Antibiotic Resistance

• Production of enzymes:
  • Beta-lactamases: Break down beta-lactam drugs.
  • Aminoglycoside-modifying enzymes: Modify aminoglycosides, making them inactive.
  • Chloramphenicol acetyl transferase: Modifies chloramphenicol, making it inactive.
• Mutation: Alteration of bacterial structures.
• Efflux pumps: Remove antibiotics from the cell.

Allergy Testing

• Allergy testing is done to determine substances that cause allergic reactions.
• Commonly used methods are skin prick or patch tests.

Antifungal Drugs

• Antifungals treat and prevent mycoses and infections.
• Types of antifungals:
  • Polyenes
  • Imidazoles
  • Triazoles
  • Allylamines
  • Inhibitors

Antiretroviral Drugs

• Antiretroviral drugs target specific viral processes.
• Types of antiretroviral drugs:
  • NRTIs (Nucleoside/Nucleotide Reverse Transcriptase Inhibitors)
  • NNRTIs (Non-Nucleoside Reverse Transcriptase Inhibitors)
  • Protease Inhibitors
  • Entry Inhibitors
  • Integrase Inhibitors

Antiprotozoan and Antihelminthic Drugs

• Chloroquine and quinacrine stop DNA synthesis.
• Metronidazole treats a wide variety of infections, by stopping the growth of bacteria and parasites.
• Niclosamide treats infections caused by cestodes.

Explore the world of antimicrobial drugs and antibiotics through this quiz. Delve into their mechanisms, history, and the concept of the zone of inhibition. This quiz is perfect for anyone looking to strengthen their knowledge in microbiology and pharmacology.