Microbiology

Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu

Chapter 15

Microbial Mechanisms of Pathogenicity - all with Video Answers

Educators

Chapter Questions

Problem 1

Which of the following would be a sign of an infection?
a. muscle aches
b. headache
c. fever
d. nausea

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Problem 2

Which of the following is an example of a noncommunicable infectious disease?
a. infection with a respiratory virus
b. food poisoning due to a preformed bacterial toxin in food
c. skin infection acquired from a dog bite
d. infection acquired from the stick of
a contaminated needle

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Problem 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?
a. iatrogenic
b. nosocomial
c. vectors
d. zoonotic

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Problem 4

Which period is the stage of disease during which the patient begins to present general signs and symptoms?
a. convalescence
b. incubation
c. illness
d. prodromal

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Problem 5

A communicable disease that can be easily transmitted from person to person is which type of disease?
a. contagious
b. iatrogenic
c. acute
d. nosocomial

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Problem 6

Which of the following is a pathogen that could not be identified by the original Koch's postulates?
a. Staphylococcus aureus
b. Pseudomonas aeruginosa
c. Human immunodeficiency virus
d. Salmonella enterica serovar Typhimurium

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Problem 7

Pathogen A has an ID $_{50}$ of 50 particles, pathogen B has an ID $_{50}$ of 1,000 particles, and pathogen $C$ has an ID $_{50}$ of $1 \times 10^{6}$ particles. Which pathogen is most virulent?
a. pathogen $\mathrm{A}$
b. pathogen B
c. pathogen $\mathrm{C}$

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Problem 8

Which of the following choices lists the steps of pathogenesis in the correct order?
a. invasion, infection, adhesion, exposure
b. adhesion, exposure, infection, invasion
c. exposure, adhesion, invasion, infection
d. disease, infection, exposure, invasion

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Problem 9

Which of the following would be a virulence factor of a pathogen?
a. a surface protein allowing the pathogen to bind
to host cells
b. a secondary host the pathogen can infect
c. a surface protein the host immune system recognizes
d. the ability to form a provirus

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Problem 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?
a. superantigen
b. endotoxin
c. exotoxin
d. leukocidin

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Problem 11

Which of the following applies to hyaluronidase?
a. It acts as a spreading factor.
b. It promotes blood clotting.
c. It is an example of an adhesin.
d. It is produced by immune cells to target pathogens.

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Problem 12

Phospholipases are enzymes that do which of the following?
a. degrade antibodies
b. promote pathogen spread through connective tissue.
c. degrade nucleic acid to promote spread of pathogen
d. degrade cell membranes to allow pathogens to escape phagosomes

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Problem 13

Which of the following is a major virulence factor for the fungal pathogen Cryptococcus?
a. hemolysin
b. capsule
c. collagenase
d. fimbriae

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Problem 14

Which of the following pathogens undergoes antigenic variation to avoid immune defenses?
a. Candida
b. Cryptococcus
c. Plasmodium
d. Giardia

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Problem 15

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

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Problem 16

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

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Problem 17

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.

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Problem 18

The concentration of pathogen needed to kill $50 \%$ of an infected group of test animals is the ________________.

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Problem 19

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.

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Problem 20

Cilia, fimbriae, and pili are all examples of structures used by microbes for ______________.

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Problem 21

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

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Problem 22

Adhesins are usually located on ____________ of the pathogen and are composed mainly of ______________ and ______________.

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Problem 23

The Shiga and diphtheria toxins target ______________ in host cells.

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Problem 24

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 ofpoint mutations in the spike proteins.

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Problem 25

Candida can invade tissue by producing the exoenzymes ______________ and ______________.

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Problem 26

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

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Problem 27

Brian goes to the hospital after not feeling well for a week. He has a fever of $38^{\circ} \mathrm{C}\left(100.4^{\circ} \mathrm{F}\right)$ and complains of nausea and a constant migraine. Distinguish between the signs and symptoms of disease in Brian's case.

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Problem 28

Describe the virulence factors associated with the fungal pathogen Aspergillus.

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Problem 29

Explain how helminths evade the immune system.

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Problem 30

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?

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Problem 31

In July 2015, a report$^{[12] }$ 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.

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Problem 32

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.

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Problem 33

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.

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Problem 34

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

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Problem 35

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

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Problem 36

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?

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