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

Physical and Chemical Control of Microbes

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. Explain the effect of a tuberculocide. What would be the effect of a pseudomonicide? What does a virustatic agent do?

2. Compare sterilization with disinfection and sanitization. Describe the relationship of the concepts of sepsis, asepsis, and antisepsis.

3. Briefly explain how the type of microorganisms present will influence the effectiveness of exposure to antimicrobial agents. Explain how the numbers of contaminants can influence the measures used to control them.

4. Precisely what is microbial death? Why does a population of microbes not die instantaneously when exposed to an antimicrobial agent?

5. Why are antimicrobial processes inhibited in the presence of extraneous organic matter?

6. Describe four modes of action of antimicrobial agents, and give a specific example of how each works.

7. Summarize the nature, mode of action, and effectiveness of moist and dry heat. Compare their effects on vegetative cells and spores.

8. How can the temperature of steam be raised above 100 degrees Celsius? Explain the relationship involved.

9. What do you see as a basic flaw in tyndallization? In boiling water devices? In incineration? In ultrasonic devices?

10. What are several microbial targets of pasteurization?

11. Explain why desiccation and cold are not reliable methods of disinfection.

12. What are some advantages of ionizing radiation as a method of control? Some disadvantages?

13. What is the precise mode of action of ultraviolet radiation? What are some disadvantages to its use?

14. What are the superior characteristics of iodophors over free iodine solutions?

15. What does it mean to lower the surface tension? What cell parts will be most affected by surface active agents?

16. Name one chemical for which the general rule that a higher concentration is more effective is not true. What is a sterilant?

17. Name the principal sporicidal chemical agents.

18. Why is hydrogen peroxide solution so effective against anaerobes?

19. Give the uses and disadvantages of the heavy metal chemical agents, glutaraldehyde, and the sterilizing gases.

20. What does it mean to say that a chemical has an oligodynamic action