Deck 25: Microbial Pathogenesis

Question 1

Yellow fever and West Nile virus are both

A) cancer causing.
B) hemorrhagic viruses.
C) close relatives of herpes virus.
D) diarrheagenic viruses.
E) flaviviruses.

Answer 1

E

Question 2

Pathogenicity islands include all of the following EXCEPT that

A) genes are not expressed as operons.
B) GC/AT ratio differs from the rest of the genome.
C) residual phage genomes flank the island.
D) they are often linked to tRNA.
E) they encode the type III protein secretion (T3SS) export systems.

Answer 2

A

Question 3

Superantigens

A) bore holes on eukaryotic cell membranes.
B) inhibit phagocytosis.
C) prevent degranulation of macrophages.
D) are antipyrogenic.
E) activate immune cells without being processed.

Answer 3

E

Question 4

Synthesis of flagella and pili filaments in Gram-negatives share which of the following attributes?

A) Protein export systems are used to deliver subunits to the outside.
B) Chaperones are not needed for protein transport.
C) There is no periplasmic stopover.
D) Flagellar and pili proteins are added in sequence intracellularly.
E) Flagellar and pili proteins do not extend beyond the periplasm.

Question 5

Exotoxins

A) are secreted by Gram-positive bacteria only.
B) primarily contain glycolipids.
C) are protein toxins made by Gram-positive and Gram-negative bacteria.
D) serve as adhesins for mucosal pathogens.
E) contain lipid A.

Question 6

Multivalent adhesion molecule 7, or MAM7, is a unique adhesion because it

A) is expressed late in an infection.
B) is found only in Gram-positive organisms.
C) is important in initiating infection.
D) decreases the LD50 of an organism.
E) acts as a toxin.

Question 7

Biofilms play a major role in enhancing bacterial virulence because

A) biofilm strains are mutants.
B) the exopolymer matrix is highly toxic and mutagenic.
C) biofilm bacteria are intracellular pathogens.
D) bacteria in biofilms are more resistant to antimicrobials and phagocytosis.
E) low bacteria density does not alert the human immune system.

Question 8

Consider two isolates, A and B. Microbe A had an LD₅₀ of 5 ´ 10⁴, while microbe B recorded an LD₅₀ of 5 ´ 10⁷. Which isolate is more virulent?

A) unable to know based on information provided
B) microbe A
C) microbe B
D) They are equally virulent.
E) The values indicate that neither one is virulent.

Question 9

The disease filariasis, commonly known as elephantiasis, is caused by a(n)

A) ectoparasite.
B) endoparasite.
C) insect.
D) bacterium.
E) fungus.

Question 10

Which of the following are also categorized as frank, or strict, pathogens?

A) parasites
B) endoparasites
C) ectoparasites
D) primary pathogens
E) opportunistic pathogens

Question 11

A life-threatening lung infection caused by biofilm formation in cystic fibrosis patients is

A) Pseudomonas aeruginosa.
B) Staphylococcus epidermidis.
C) Mycobacterium tuberculosis.
D) Vibrio cholerae.
E) Bordetella pertussis.

Question 12

The term used to designate how many bacteria or viruses are required to kill 50% of an experimental group of hosts is

A) ID50.
B) LD50.
C) pathogenicity.
D) infectivity.
E) virulence.

Question 13

Which of the following statements is NOT correct about disease reservoirs?

A) Reservoirs are mammals or birds, but not insects.
B) A vector can be the reservoir of a disease.
C) A reservoir is an integral part of the disease cycle.
D) Disease-control measures must consider the biological reservoir.
E) A reservoir is ultimately the source of infection in a population.

Question 14

Type I and Type IV pili both

A) are similar in mode of secretion.
B) are mannose resistant.
C) have an assembly that does not involve the secA general secretory pathway.
D) are encoded by a pathogenicity island.
E) are exclusively used for pathogenesis.

Question 15

A chef cut her finger accidentally. The next morning, she felt pain and warmth and had a little swelling and redness on that finger (which are signs of inflammation). By that night, she was just fine. Which of the following pertains to the chef?

A) She had an overt microbial disease.
B) She had an infection.
C) The inflammation was a response to the cut, not a microbe.
D) Microbial toxins, not the vegetative cells, induced inflammation.
E) The cut introduced ectoparasites that could not survive.

Question 16

The likely mode of transmission of a bacterial disease in which incidence increases with a prolonged warm summer is

A) direct transmission.
B) airborne transmission.
C) insect vector transmission.
D) common source fomite.
E) sexual transmission.

Question 17

Which of the following diseases is transmitted by the mosquito Aedes aegypti?

A) yellow fever
B) Ebola
C) epidemic typhus
D) listeriosis
E) SARS

Question 18

The toxin gene in Corynebacterium diphtheriae is located on

A) the plasmid.
B) mobile genes called transposons.
C) bacterial chromosomes.
D) lysogenic phage genomes.
E) the plasma membrane.

Question 19

The current classification of bacteria pili is based on ________ rather than ________.

A) phenotype; function
B) function; amino acid sequence
C) protein sequence; phenotype
D) origin; protein sequence
E) size; phenotype

Question 20

An example of vertical transmission of infectious agents is

A) Staphylococcus spp. gaining antibiotic resistance genes through conjugation.
B) HIV passing from mother to child in utero.
C) an infectious ameba obtained from a water sample.
D) influenza being passed by a sneeze.
E) hepatitis being transmitted by an infected needle stick.

Question 21

Which of the following does NOT result from the release of endotoxin from Gram-negative bacteria?

A) fever
B) activation of the alternate complement pathway
C) vasodilation
D) hypertension
E) shock

Question 22

Which of the following statements is NOT correct about a patient who died from endotoxin pathologies?

A) Disseminated intravascular coagulation may have contributed to death.
B) The methicillin-resistant Staphylococcus aureus, or MRSA, superbug is a likely suspect.
C) The patient may have died from hypotension.
D) The patient may not have run a fever if AIDS was present.
E) The lipid A in the endotoxin is responsible for the virulence.

Question 23

Protein A helps Staphylococcus aureus avoid

A) antibiotics.
B) apoptosis.
C) phagocytosis.
D) cytotoxic T cells.
E) phagosome-lysosome fusion.

Question 24

A possible role for quorum sensing in pathogenicity is that it

A) detects and responds to the pH as an indicator of the environment.
B) delays production of toxins that may alert the host to the presence of the bacteria.
C) monitors and responds to concentrations of ions such as magnesium.
D) senses and responds to the population of phagocytes at the infection site.
E) helps the pathogen escape the adaptive immune response.

Question 25

Bacteria that exhibit antigenic shifts and phase variations will most likely cause

A) host immunity.
B) recurrent infections in the exposed host.
C) death each time a host is infected.
D) subclinical infections.
E) mild, acute infections.

Question 26

Which of the following produces a toxin that disrupts protein synthesis?

A) Clostridium perfringens
B) Shigella dysenteriae
C) Listeria monocytogenes
D) Staphylococcus aureus
E) Bacillus anthracis

Question 27

Which of the following protein secretory systems injects effector molecules directly from the bacterial cytoplasm into the host cytoplasm?

A) type I
B) type II
C) type III
D) type IV
E) types I, II, III, and IV

Question 28

Petechiae, which result from large amounts of endotoxin, are distinguished by which symptom?

A) diarrhea
B) a pseudomembrane
C) elephantiasis
D) fever
E) a rash

Question 29

The enterotoxigenic Escherichia coli heat-labile toxin

A) damages membranes.
B) increases protein synthesis.
C) activates second messenger pathways.
D) activates immune response.
E) acts as a capsule.

Question 30

The cholera and Escherichia coli (traveler's diarrhea) toxins ________, leading to high levels of cAMP in cells.

A) ADP ribosylate the Gs factor
B) ADP ribosylate adenyl cyclase
C) inactivate ATP
D) are bacterial adenylate cyclase
E) phosphorylate the G factor

Question 31

What type of toxin is the alpha hemolysin of Staphylococcus aureus?

A) protein synthesis inhibitor
B) protease
C) superantigen
D) cell membrane disruptor
E) second messenger pathway disruptor

Question 32

Toxins with ADP ribosyltransferase activity cause

A) membrane pore formation.
B) immune system activation.
C) proteolytic degradation of host proteins.
D) adenylate cyclase inhibition.
E) inhibition of elongation factor 2.

Question 33

E. coli O157:H7 has a very low infectious dose because

A) it is encapsulated.
B) disease results from a synergistic action with Shigella.
C) it is resistant to usually lethal gastric acid.
D) the intestine has many receptors for the toxin.
E) it secretes a superantigen.

Question 34

The anthrax, Escherichia coli, cholera, and Bordetella toxins all

A) inhibit protein synthesis.
B) possess ADP ribosyltransferase activity.
C) cause diarrhea.
D) disrupt the cell membrane.
E) trigger apoptosis.

Question 35

Binding of the protein ________ of the EPEC pathogenicity system directly triggers a remarkable reorganization of host cellular cytoskeletal components.

A) actin
B) SPI-1
C) intimin
D) Nef
E) Ivet

Question 36

Which of the following is classified as an intracellular bacterial pathogen?

A) HIV
B) Streptococcus mutans
C) Listeria monocytogenes
D) Neisseria gonorrhoeae
E) Bacillus anthracis

Question 37

Which of the following species causes whooping cough?

A) Streptococcus mutans
B) Staphylococcus aureus
C) Bordetella pertussis
D) Neisseria gonorrhoeae
E) Mycoplasma

Question 38

Thick polysaccharide capsules are important virulence assets for

A) Escherichia coli and Vibrio cholera.
B) Clostridium tetani and Bacillus anthracis.
C) Neisseria gonorrhoeae and Streptococcus pneumonia.
D) Salmonella spp. and Staphylococcus aureus.
E) Helicobacter pylori and Enterobacter cloacae.

Question 39

The ability to survive in the harsh environment of the phagolysosome is a virulence factor produced by

A) uropathogenic Escherichia coli.
B) Vibrio cholera.
C) Bordetella pertussis.
D) Helicobacter pylori.
E) Coxilla burnetti.

Question 40

Which of the following is a nonproteinaceous, yet toxic, compound found in all Gram-negative bacteria?

A) endotoxin
B) exotoxin
C) type I pili
D) type III pili
E) type IV pili

Question 41

Briefly describe three classic modes of action of bacterial toxins. How are they similar? How are they different?

Question 42

Agent A has an LD₅₀ of 400. Agent B has an LD₅₀ of 600. Which is the more pathogenic agent, A or B? What is the relationship between this measure and microbial virulence?

Question 43

Which of the following techniques would be used to identify unknown virulence genes that are only expressed in the host?

A) in situ hybridization of cultured bacteria
B) creating a genomic library of open reading frames of pathogen
C) mutational studies in vitro
D) culture techniques
E) in vivo expression technology

Question 44

Koch's molecular postulates were originally formulated by

A) Robert Koch.
B) Louis Pasteur.
C) Thomas Rivers.
D) Matthew Lawrenz.
E) Stanley Falkow.

Question 45

Type IV pili are essential for the interaction of Neisseria meningitidis with brain endothelial cells. Describe the difference between the type IV and type I pili binding, and explain why knowing the type of binding is important in pathogenesis.

Question 46

Tropheryma whipplei is the causative agent for Whipple's disease. It could not be cultured until recently, when the genomic data showed that it

A) was auxotrophic for some amino acids.
B) was an obligate intracellular pathogen.
C) needed a helper virus to grow.
D) needed high levels of iron.
E) is a virus that needs cell culture.

Question 47

Describe what is happening at step 1 in the figure below.

Question 48

What is the rationale for designating disease-causing protozoa and worms as parasites, not as pathogens?

Question 49

Salmonella and Shigella both

A) produce shiga toxin.
B) are Gram-positive rods.
C) are resistant to gastric acid.
D) cause typhoid fever.
E) are facultative intracellular pathogens.

Question 50

Autophagy is used by a host cell to

A) activate G-proteins.
B) regulate phagocytosis.
C) scavenge nutrients from damaged organelles.
D) fight extracellular pathogens.
E) induce apoptosis.

Question 51

How does a pathogenicity island increase the "fitness" of a microorganism (pathogen) to interact with a host and cause disease?

Question 52

Identify the parts labeled C, D, E, G, L, M, N in the figure below, and state what their purpose is.

Question 53

Which of the following types of information CANNOT be derived from the full genome of a noncultured bacterial pathogen?

A) nutritional requirements
B) toxin production
C) infectious and lethal doses
D) pathogenic islands
E) cell receptor binding and tissue tropism

Question 54

Mycobacterium, Trypanosomia, and Leishmania spp. are all unique in that once they are intracellular, they down-regulate the IFN-gamma receptor, causing

A) immune-response suppression.
B) opsonization.
C) complement activation.
D) superantigen reactions.
E) high fever responses.

Question 55

Which of the following bacteria would you expect to cause the most severe blood disease in a susceptible host?

A) a rapidly growing encapsulated bacteria
B) a flagellated acidophile
C) a barophilic strain
D) a piliated slow-growing bacteria
E) a halophilic psychrophile

Question 56

Which of the following is considered a virulence factor?

A) TNF-Alpha
B) RNA
C) IFN-gamma
D) Strep. pyogenes
E) capsules

Question 57

Microbes can be transmitted indirectly from one person to another by inanimate objects, collectively called fomites. Describe the role of fomites in the spread of influenza.

Question 58

Define a fomite and give at least two specific examples.

Question 59

Which organism did Koch use to synthesize his two postulates?

A) Bacillus anthracis
B) Staph. aureus
C) Ebola
D) SARS
E) MERs

Question 60

What characteristics of a pathogen distinguish it from a commensal, in terms of its ability to infect and replicate within a eukaryotic host?

Question 61

What are ubiquitination signals? Describe how a microbe can redirect these signals for its own purposes.

Question 62

Two Streptococcus pneumoniae strains, agent 1 and agent 2, are administered to groups of animals at different doses. Mortality rates are then measured for the animals that received each dose level of each agent. Agent 1 is found to have an LD₅₀ of 400. Agent 2 is found to have an LD₅₀ of 600. Which one is producing a capsule and which one is not? How do you know?

Question 63

What process is occurring in the figure below? Describe that process.

Question 64

There is no host cell receptor for the enteropathogenic Escherichia coli intimin adhesion. How does this pathogen successfully colonize human intestines?

Question 65

Why is a microbial agent that prevents phagosome-lysosome fusion more virulent as an intracellular pathogen than one that is not?

Question 66

Describe what is occurring in the figure below.

Question 67

Describe what kind of assembly is occurring in the figure below, and identify the molecules that are present.

Question 68

Describe the use of digital gene expression (DGE) in host-pathogen relations. How does it work and what information can it tell us?

Question 69

What would be expected to happen to the Helicobacter pylori bacteria in a patient who has taken a large amount of antacids in the last month?

Question 70

Diphtheria toxin is a classic AB exotoxin. How does it cause host cell damage?