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# Chapter 12 Notes The goal of antimicrobial chemotherapy is simple: administer a drug that destroys the infectious agent without harming the host's cells. It is a difficult goal to achieve * **Antibiotics**: Substances produced by natural metabolic processes of microorganisms that can inhibit or...

# Chapter 12 Notes The goal of antimicrobial chemotherapy is simple: administer a drug that destroys the infectious agent without harming the host's cells. It is a difficult goal to achieve * **Antibiotics**: Substances produced by natural metabolic processes of microorganisms that can inhibit or destroy other microorganisms. Drugs should be *selectively toxic*, meaning they kill or inhibit the growth of microbes without damaging host tissues. * **Cell Walls**: Most bacteria have a rigid peptidoglycan cell wall that protects them from hypotonic environments. They must constantly synthesize new peptidoglycan. * **Polymyxins**: Interact with membrane phospholipids, causing leakage of proteins and nucleic acids, particularly in gram-negative bacteria. * **Daptomycin**: Shows selectivity for gram-positive bacteria * **Antimicrobial Drugs**: These drugs interfere with nucleic acid synthesis in several ways * **Blocking Synthesis of Nucleotides**: Inhibiting replication or stopping transcription * **Inhibiting Protein Synthesis**: Several drugs inhibit protein synthesis reaction with the ribosome-mRNA complex * **Penicillin G**: First antibiotic, narrow spectrum, cannot be given orally * **Polymyxins**: A mixture of antibiotic polypeptides from *Bacillus polymyxa*, particularly effective against gram-negative bacteria. Toxic to the kidney * **Rifampin**: Disrupts nucleic acids by blocking the action of RNA polymerase, preventing transcription * **Tetracyclines**: A group of broad-spectrum antibiotics with a complex 4-ring structure.