Chapter 14

  • Chemotherapeutic Agents: Agents used to treat infections caused by microbes

    • Antibiotics: Natural substances made by microbes to kill/inhibit other microbes.

    • Commonly understood as drugs for bacterial infections.

    • Synthetic Drugs: Chemically made to mimic natural compounds/drugs; including antivirals.

    • Semisynthetic Drugs: Modified natural antibiotics (derivatives).

    • Alexander Fleming: Discovered Penicillin in 1928, mass-produced in the 1940s

    • Paul Ehrlich: Discovered an early antimicrobial for syphilis, Compound 606

    • Selman Waksman: Found antibiotics in soil bacteria (actinomycetes)

    Choosing Antimicrobials depends on:

  • Microbial Sensitivity: The susceptibility of bacteria to drugs.

  • Drug Nature & Spectrum: Range of effectiveness against different microbes.

  • Patient Condition: Health and other medications affect choices.

  • Adverse Side Effects: Risks associated with drugs, considering possible complications.

  • Antibiotic Resistance: Previous exposure can lead to drug resistance.

    Drug Resistance Types:

    • Chromosomal Resistance: Genetic mutations in bacteria that cause resistance.

    • Plasmid-borne Resistance: Genetic material that can be transferred between bacteria affecting how easily it can be harmed

Antibiotic Side Effects

  • Allergic Reactions: Immune response to antibiotics.

  • Toxicity: Impact on patient health due to therapeutic index variability (narrow TI = higher risk)

    • Therapeutic Index: TI = LD50 / ED50

      • LD50 = dose that kills 50%

      • ED50 = effective dose for 50%

    • Higher TI = safer drug

  • Microbiome Disruption: Antibiotics may kill beneficial bacteria, leading to superinfections (C. difficile).

    Antifungal Drugs

    • Target ergosterol in fungal membranes (not in humans).

    • Antiprotozoan Drugs

      • Quinine (malaria), Metronidazole, Pyrimethamine.

Cell Wall Inhibitors

  • Penicillins (beta-lactams): Stop bacteria from building their outer wall, so they burst and die.

  • Bacitracin: Blocks parts needed to make the wall from getting to the right place.

  • Protein Synthesis Inhibitors: Stop bacteria from making proteins by messing with their "protein-making machines" (ribosomes).

Folic Acid Blockers

  • Sulfonamides: Stop bacteria from making folic acid, which they need to build DNA and grow.

  • Probiotics: Live microorganisms that improve intestinal flora (gut) and inhibit pathogenic growth, bad germs to keep stomach healthy like germ killers, bacteriocins

  • Prebiotics: Nutrients that support beneficial microbial growth (good germs in your gut) like fiber