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Foundations in Microbiology, 4/e
Kathleen Park Talaro, Pasadena City College
Arthur Talaro

Drugs, Microbes, Host: The Elements of Chemotherapy

Concept Questions

Take some time to write answers to these questions. If you can answer them, you have a good grasp of the material!

1. Differentiate between antibiotics and synthetic drugs.

2. Differentiate between narrow-spectrum and broad-spectrum antibiotics. Can you determine why some drugs have narrower spectra than others? (Hint: Look at their mode of action.) How might one determine whether a particular antimicrobic is broad- or narrow-spectrum?

3. What is the major source of antibiotics? What appears to be the natural function of antibiotics?

4. Using the following diagram as a guide, briefly explain how the three factors in drug therapy interact. What drug characteristics will make treatment most effective? What are the major aims of new antimicrobic drugs? Which of your answers to the prior question do you think is the most important?

5. Explain the major modes of action of antimicrobial drugs, and give an example of each. What is competitive inhibition? What is the basic reason that a metabolic analog molecule can inhibit metabolism? What are the long-term effects of drugs that block transcription? Why would a drug that blocks translation on the ribosomes of bacteria also affect human cells? Why do drugs that act on bacterial and fungal membranes generally have high toxicity?

6. Explain the phenomenon of drug resistance from the standpoint of microbial genetics (include a description of R factors). How can one test for drug resistance? Multiple drug resistance is becoming increasingly common in microorganisms. Explain how one bacterium can acquire resistance to several drugs.

7. Explain four general ways that microbes evade the effects of drugs. What is the effect of beta-lactamase?

8. What causes mutated or plasmid-altered strains of drug-resistant microbes to persist in a population?

9. Construct a chart that summarizes the modes of action and applications of the major groups of antibacterial drugs (antibiotics and synthetics), antifungal drugs, antiparasitic drugs, and antiviral drugs.

10. Explain why there are so few antifungal, antiparasitic, and antiviral drugs. What effect do nitrogen-base analogs have upon viruses? Summarize the origins and biological actions of interferon.

11. Generally overview the adverse effects of antimicrobic drugs on the host. On what basis can one explain allergy to drugs? Describe the stages in a superinfection.

12. Outline the steps in antimicrobic susceptibility testing. Compare the interpretation of the Kirby-Bauer technique with the MIC technique. What is the therapeutic index, and how is it used?