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9: Antimicrobial Drugs

  • Page ID
    93532
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    In nature, some microbes produce substances that inhibit or kill other microbes that might otherwise compete for the same resources. Humans have successfully exploited these abilities, using microbes to mass-produce substances that can be used as antimicrobial drugs. Since their discovery, antimicrobial drugs have saved countless lives, and they remain an essential tool for treating and controlling infectious disease. But their widespread and often unnecessary use has had an unintended side effect: the rise of multidrug-resistant microbial strains. In this chapter, we will discuss how antimicrobial drugs work, why microbes develop resistance, and what health professionals can do to encourage responsible use of antimicrobials.

    Figure \(\PageIndex{1}\): First mass produced in the 1940s, penicillin was instrumental in saving millions of lives during World War II and was considered a wonder drug.\(^{[1]}\) Today, overprescription of antibiotics (especially for childhood illnesses) has contributed to the evolution of drug-resistant pathogens. (credit left: modification of work by Chemical Heritage Foundation; credit right: modification of work by U.S. Department of Defense)

    Chapter Outline

    • 9.1: History of Chemotherapy and Antimicrobial Discovery
    • 9.2: Fundamentals of Antimicrobial Chemotherapy
    • 9.3: Mechanisms of Antibacterial Drugs
    • 9.4: Mechanisms of Other Antimicrobial Drugs
      Because fungi, protozoans, and helminths are eukaryotic organisms like human cells, it is more challenging to develop antimicrobial drugs that specifically target them. Similarly, it is hard to target viruses because human viruses replicate inside of human cells.
    • 9.5: Drug Resistance
      Antimicrobial resistance is on the rise and is the result of selection of drug-resistant strains in clinical environments, the overuse and misuse of antibacterials, the use of subtherapeutic doses of antibacterial drugs, and poor patient compliance with antibacterial drug therapies. Drug resistance genes are often carried on plasmids or in transposons that can undergo vertical transfer easily and between microbes through horizontal gene transfer.
    • 9.6: Testing the Effectiveness of Antimicrobials
      The Kirby-Bauer disk diffusion test helps determine the susceptibility of a microorganism to various antimicrobial drugs. However, the zones of inhibition measured must be correlated to known standards to determine susceptibility and resistance, and do not provide information on bactericidal versus bacteriostatic activity, or allow for direct comparison of drug potencies. Antibiograms are useful for monitoring local trends in antimicrobial resistance/susceptibility.
    • 9.7: Current Strategies for Antimicrobial Discovery
      With the continued evolution and spread of antimicrobial resistance, and now the identification of pan-resistant bacterial pathogens, the search for new antimicrobials is essential for preventing the postantibiotic era.
    • 9.8: Review Questions

    Footnotes

    1. “Treatment of War Wounds: A Historical Review.” Clinical Orthopaedics and Related Research 467 no. 8 (2009):2168–2191.


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