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Lecture 2

Lecture 2. Antimicrobial Chemotherapy Antimicrobial Mechanisms of Action Dr.: Abeer El-Sherbiny. Microbial Sources of Antibiotics. Different types of antimicrobial Chemotherapy. Antibacterial Chemotherapy Antiviral Chemotherapy Antifungal Chemotherapy

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Lecture 2

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  1. Lecture 2 Antimicrobial Chemotherapy Antimicrobial Mechanisms of Action Dr.: Abeer El-Sherbiny

  2. Microbial Sources of Antibiotics

  3. Different types of antimicrobial Chemotherapy • Antibacterial Chemotherapy • Antiviral Chemotherapy • Antifungal Chemotherapy • Antiprotozoan (Antiparasitic) Chemotherapy Antibacterials • Relatively easy to develop and find with low toxicity because prokaryotic cells are very different from host cells. Antihelminthic, antiprotozoan, and antifungal drugs • More difficult to develop because eukaryotic cells resemble human cells. Antivirals • Most difficult to develop because virus reproduces using host cell enzymes and machinery.

  4. Characteristics of microbes

  5. Mechanisms (Mode) of Action of Antimicrobial Chemotherapy • Bacteria have their own enzymes for cell wall formation, Protein synthesis, DNA replication, RNA synthesis & Synthesis of essential metabolites • Viruses use host enzymes inside host cells • Fungi and protozoa have own eukaryotic enzymes • The more similar the pathogen and host enzymes, the more side effects the antimicrobials will have

  6. Mechanisms of Antimicrobial Action • Mechanisms of action of Antibacterial Chemotherapy • Inhibit cell wall synthesis • Inhibit protein synthesis • Inhibit nucleic acid synthesis • Injury to plasma membrane • Inhibit synthesis of essential metabolites

  7. The Mechanisms of Action of Antimicrobial Chemotherapy

  8. Inhibition of Cell Wall Synthesis: Interfere with peptidoglycan synthesis. • Result in cell lysis. • E.g.: Penicillin, cephalosporins, bacitracin and vancomycin. • Inhibition of Protein Synthesis: Interfere with prokaryotic (70S) ribosomes • Most have broad spectrum of activity • E.g.: Tetracycline, chloramphenicol, erythromycin, and streptomycin.

  9. Gram positive Gram negative

  10. Injury to the Plasma Membrane: Cause changes in membrane permeability. • Result in loss of metabolites and/or cell lysis. • E.g.: Polymyxin B • Inhibition of Nucleic Acid (DNA/RNA) Synthesis: Interfere with DNA replication and transcription. • May be toxic to human cells. • E.g.: Rifampin and quinolones. • Inhibition of Synthesis of Essential Metabolites: Involve competitive inhibition of key enzymes. • Closely resemble normal substrate of enzyme. • E.g.: Sulfa drugs inhibit the synthesis of folic acid.

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