# Chapter 12 Exercises

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## Review Questions for Chapter 12

### Multiple Choice

1) Which of the following would be a sign of an infection?

1. muscle aches
3. fever
4. nausea

2) Which of the following is an example of a noncommunicable infectious disease?

1. infection with a respiratory virus
2. food poisoning due to a preformed bacterial toxin in food
3. skin infection acquired from a dog bite
4. infection acquired from the stick of a contaminated needle

3) During an oral surgery, the surgeon nicked the patient’s gum with a sharp instrument. This allowed Streptococcus, a bacterium normally present in the mouth, to gain access to the blood. As a result, the patient developed bacterial endocarditis (an infection of the heart). Which type of disease is this?

1. iatrogenic
2. nosocomial
3. vectors
4. zoonotic

4) Which period is the stage of disease during which the patient begins to present general signs and symptoms?

1. convalescence
2. incubation
3. illness
4. prodromal

5) A communicable disease that can be easily transmitted from person to person is which type of disease?

1. contagious
2. iatrogenic
3. acute
4. nosocomial

6) Which of the following is a pathogen that could not be identified by the original Koch’s postulates?

1. Staphylococcus aureus
2. Pseudomonas aeruginosa
3. Human immunodeficiency virus
4. Salmonella enterica serovar Typhimurium

7) Pathogen A has an ID50 of 50 particles, pathogen B has an ID50 of 1,000 particles, and pathogen C has an ID50 of 1 × 106 particles. Which pathogen is most virulent?

1. pathogen A
2. pathogen B
3. pathogen C

8) Which of the following choices lists the steps of pathogenesis in the correct order?

4. disease, infection, exposure, invasion

9) Which of the following would be a virulence factor of a pathogen?

1. a surface protein allowing the pathogen to bind to host cells
2. a secondary host the pathogen can infect
3. a surface protein the host immune system recognizes
4. the ability to form a provirus

10) You have recently identified a new toxin. It is produced by a gram-negative bacterium. It is composed mostly of protein, has high toxicity, and is not heat stable. You also discover that it targets liver cells. Based on these characteristics, how would you classify this toxin?

1. superantigen
2. endotoxin
3. exotoxin
4. leukocidin

11) Which of the following applies to hyaluronidase?

1. It acts as a spreading factor.
2. It promotes blood clotting.
3. It is an example of an adhesin.
4. It is produced by immune cells to target pathogens.

12) Phospholipases are enzymes that do which of the following?

2. promote pathogen spread through connective tissue.
4. degrade cell membranes to allow pathogens to escape phagosomes

13) Which of the following is a major virulence factor for the fungal pathogen Cryptococcus?

1. hemolysin
2. capsule
3. collagenase
4. fimbriae

14) Which of the following pathogens undergoes antigenic variation to avoid immune defenses?

1. Candida
2. Cryptococcus
3. Plasmodium
4. Giardia

15) Which is the most common type of biological vector of human disease?

1. viruses
2. bacteria
3. mammals
4. arthropods

16) A mosquito bites a person who subsequently develops a fever and abdominal rash. What type of transmission would this be?

1. mechanical vector transmission
2. biological vector transmission
3. direct contact transmission
4. vehicle transmission

17) Cattle are allowed to pasture in a field that contains the farmhouse well, and the farmer’s family becomes ill with a gastrointestinal pathogen after drinking the water. What type of transmission of infectious agents would this be?

1. biological vector transmission
2. direct contact transmission
3. indirect contact transmission
4. vehicle transmission

18) A blanket from a child with chickenpox is likely to be contaminated with the virus that causes chickenpox (Varicella-zoster virus). What is the blanket called?

1. fomite
2. host
3. pathogen
4. vector

19) Which of the following would NOT be considered an emerging disease?

1. Ebola hemorrhagic fever
2. West Nile virus fever/encephalitis
3. Zika virus disease
4. Tuberculosis

20) Which of the following would NOT be considered a reemerging disease?

1. Drug-resistant tuberculosis
2. Drug-resistant gonorrhea
3. Malaria
4. West Nile virus fever/encephalitis

21) Which of the following factors can lead to reemergence of a disease?

1. A mutation that allows it to infect humans
2. A period of decline in vaccination rates
3. A change in disease reporting procedures
4. Better education on the signs and symptoms of the disease

22) Why are emerging diseases with very few cases the focus of intense scrutiny?

1. They tend to be more deadly
2. They are increasing and therefore not controlled
3. They naturally have higher transmission rates
4. They occur more in developed countries

### Fill-in-the-Blanks

23) A difference between an acute disease and chronic disease is that chronic diseases have an extended period of __________.

24) A person steps on a rusty nail and develops tetanus. In this case, the person has acquired a(n) __________ disease.

25) A(n) __________ pathogen causes disease only when conditions are favorable for the microorganism because of transfer to an inappropriate body site or weakened immunity in an individual.

26) The concentration of pathogen needed to kill 50% of an infected group of test animals is the __________.

27) A(n) __________ infection is a small region of infection from which a pathogen may move to another part of the body to establish a second infection.

28) Cilia, fimbriae, and pili are all examples of structures used by microbes for __________.

29) The glycoprotein adhesion gp120 on HIV must interact with __________ on some immune cells as the first step in the process of infecting the cell.

30) Adhesins are usually located on __________ of the pathogen and are composed mainly of __________ and __________.

31) The Shiga and diphtheria toxins target __________ in host cells.

32) Antigenic __________ is the result of reassortment of genes responsible for the production of influenza virus spike proteins between different virus particles while in the same host, whereas antigenic __________ is the result of point mutations in the spike proteins.

33) Candida can invade tissue by producing the exoenzymes __________ and __________.

34) The larval form of Schistosoma mansoni uses a __________ to help it gain entry through intact skin.

35) The ________ collects data and conducts epidemiologic studies in the United States.

36) ________occurs when an infected individual passes the infection on to other individuals, who pass it on to still others, increasing the penetration of the infection into the susceptible population.

37) A batch of food contaminated with botulism exotoxin, consumed at a family reunion by most of the members of a family, would be an example of a ________ outbreak.

38) A patient in the hospital with a urinary catheter develops a bladder infection. This is an example of a(n) ________ infection.

39) A ________ is an animal that can transfer infectious pathogens from one host to another.

40) The ________ collects data and conducts epidemiologic studies at the global level.

41) Brian goes to the hospital after not feeling well for a week. He has a fever of 38 °C (100.4 °F) and complains of nausea and a constant migraine. Distinguish between the signs and symptoms of disease in Brian’s case.

42) Describe the virulence factors associated with the fungal pathogen Aspergillus.

43) Explain how helminths evade the immune system.

44) During an epidemic, why might the prevalence of a disease at a particular time not be equal to the sum of the incidences of the disease?

45) In what publication would you find data on emerging/reemerging diseases in the United States?

46) What activity did John Snow conduct, other than mapping, that contemporary epidemiologists also use when trying to understand how to control a disease?

47) Differentiate between droplet vehicle transmission and airborne transmission.

### Critical Thinking

48) Two periods of acute disease are the periods of illness and period of decline. (a) In what way are both of these periods similar? (b) In terms of quantity of pathogen, in what way are these periods different? (c) What initiates the period of decline?

49) In July 2015, a report 1 was released indicating the gram-negative bacterium Pseudomonas aeruginosa was found on hospital sinks 10 years after the initial outbreak in a neonatal intensive care unit. P. aeruginosa usually causes localized ear and eye infections but can cause pneumonia or septicemia in vulnerable individuals like newborn babies. Explain how the current discovery of the presence of this reported P. aeruginosa could lead to a recurrence of nosocomial disease.

50) Diseases that involve biofilm-producing bacteria are of serious concern. They are not as easily treated compared with those involving free-floating (or planktonic) bacteria. Explain three reasons why biofilm formers are more pathogenic.

51) A microbiologist has identified a new gram-negative pathogen that causes liver disease in rats. She suspects that the bacterium’s fimbriae are a virulence factor. Describe how molecular Koch’s postulates could be used to test this hypothesis.

52) Acupuncture is a form of alternative medicine that is used for pain relief. Explain how acupuncture could facilitate exposure to pathogens.

53) Two types of toxins are hemolysins and leukocidins. (a) How are these toxins similar? (b) How do they differ?

54) Imagine that a mutation in the gene encoding the cholera toxin was made. This mutation affects the A-subunit, preventing it from interacting with any host protein. (a) Would the toxin be able to enter into the intestinal epithelial cell? (b) Would the toxin be able to cause diarrhea?

55) Why might an epidemiological population in a state not be the same size as the number of people in a state? Use an example.

56) Many people find that they become ill with a cold after traveling by airplane. The air circulation systems of commercial aircraft use HEPA filters that should remove any infectious agents that pass through them. What are the possible reasons for increased incidence of colds after flights?

57) An Atlantic crossing by boat from England to New England took 60–80 days in the 18th century. In the late 19th century the voyage took less than a week. How do you think these time differences for travel might have impacted the spread of infectious diseases from Europe to the Americas, or vice versa?

###### Footnotes

1. C. Owens. “P. aeruginosa survives in sinks 10 years after hospital outbreak.” 2015. http://www.healio.com/infectious-dis...pital-outbreak

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