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

Microbe-Human Interactions: Infection and Disease

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 contamination, infection, and disease. What are the possible outcomes in each?

2. How are infectious diseases different from other diseases?

3. Name the general body areas that are sterile. Why is the inside of the intestine not sterile like many other organs?

4. What causes variations in the flora of the newborn intestine?

5. What factors influence how the flora of the vagina develops?

6. Why must axenic young be delivered by cesarian section?

7. Explain several ways that true pathogens differ from opportunistic pathogens.

8. Distinguish between pathogenicity and virulence. Define virulence factors, and give examples of them in gram-positive and gram-negative bacteria, viruses, and parasites.

9. Describe the course of infection from contact with the pathogen to its exit from the host.

10. Explain why most microbes are limited to a single portal of entry. For each portal of entry, give a vehicle that carries the pathogen and the course it must travel to invade the tissues. Explain how the portal of entry could differ from the site of infection.

11. Differentiate between exogenous and endogenous infections.

12. What factors possibly affect the size of the infectious dose? Name five factors involved in microbial adhesion.

13. Which body cells or tissues are affected by hemolysins, leukocidins, hyaluronidase, kinases, tetanus toxin, pertussis toxin, and enterotoxin?

14. Compare and contrast: systemic versus local infections; primary versus secondary infections; infection versus intoxication.

15. What is the difference between signs and symptoms? (First put yourself in the place of a patient with an infection and then in the place of a physician examining you. Describe what you would feel and what the physician would detect upon examining the affected area.)

16. What are some important considerations about the portal of exit? Name some examples of infections and their portals of exit.

17. Complete the table:

Chemical make-up
General source
Degree of toxicity
Effects on cells
Symptoms in disease

18. Outline the science of epidemiology and the work of an epidemiologist. Using the following statistics, based on number of reported cases, can you determine which show endemic, sporadic, or epidemic patterns? How can you determine each type?

United States RegionDisease Statistics
Northeast 131182
East Coast 824854
Central 761897
Southeast 213294
West 810822
Total cases 27393049
Leprosy (Hansen's disease)19951997
Northeast 40
East Coast 1810
Central 78
Southeast 2216
West 7891
Total cases 129125
Northeast 21
East Coast 92
Central 62
Southeast 41
West 164
Total cases 3710

Explain what would have to occur for these diseases to have a pandemic distribution.

19. Distinguish between mechanical and biological vectors, giving one example of each.

20. Explain what it means to be a carrier of infectious disease. Describe four ways that humans can be carriers. What is epidemiologically and medically important about carriers in the population?

21. Explain the precise difference between communicable and non-communicable infectious diseases. Between direct and indirect modes of transmission. Between vectors and vehicles as modes of transmission.

22. Nosocomial infections can arise from what two general sources? From this chapter and figure 20.7 outline the major agents involved in nosocomial infections. Do they tend to be true pathogens or opportunists? Outline the two types of hospital asepsis and define isolation. What is the work of an infection control officer?

23. List the main features of Koch’s postulates. Why is it so difficult to prove them for some diseases?