Antimicrobial agents

Updates for World TB Day, March 2024

  • New TB Drugs: BDQ, DLM, LZD, CFZ

  • Various regimens and ongoing trials identified.

Chemotherapy and Drug Discovery

  • Chemotherapy Definition: Use of chemicals to kill pathogens without harming the host (Paul Ehrlich).

  • Key Historical Discoveries:

    • 1910: Salvarsan for syphilis (Ehrlich).

    • 1928: Penicillin discovered by Fleming.

    • 1935: Prontosil discovered by Domagk.

    • 1943: Streptomycin discovered by Waksman.

Types of Antimicrobial Agents

  • Definitions:

    • Chemotherapeutic agents: Non-toxic, used internally for infections.

    • Antiseptics: Kill microorganisms on living tissues (e.g., ethanol).

    • Disinfectants: Kill microorganisms on non-living objects (e.g., chlorine).

Categories of Antimicrobials

  • Antimicrobials: Natural/synthetic compounds against microorganisms.

  • Antibiotics: Produced naturally to inhibit/kills other microorganisms.

Antimicrobial Effectiveness

  • Should be non-toxic, effective, stable in vivo, active at low concentrations, and easy to manufacture.

Modes of Action

  • Bacteriostatic vs. Bactericidal: Inhibit growth vs. kill microbes.

Susceptibility Testing

  • MIC: Minimum inhibitory concentration for growth inhibition.

  • MBC: Minimum bactericidal concentration killing 99.9% of inoculum.

  • Methods: Micro-dilution, solid media, disc assay, E-test.

Drug Interactions

  • Additivity: Combined effects equal sum of effects of individual drugs.

  • Synergism: Combined effect greater than the sum of individual effects.

  • Antagonism: Combined effects less than additive; one drug reduces the effect of the other.

Treatment of Infections

  • Tuberculosis: Commonly treated with Isoniazid, Ethambutol, Pyrazinamide, Rifampicin.

  • Viral Treatments: Include Amantadine, Acyclovir, NRTIs (e.g., Abacavir).

Global TB Drug Pipeline (2024)

  • Overview of drugs in various stages of development from preclinical to market approvals.

Alternative Treatments

  • Phage therapy, probiotics, immunotherapy, gene therapy.

Additional Tasks

  • Complete revision table, read glossary, Chapter 5 in Medical Microbiology textbook (pp. 54-68).