Deck 25: Microbial Pathogenesis

Question 1

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

A) He had an overt microbial disease.
B) He 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.

Answer 1

B

Question 2

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

Answer 2

C

Question 3

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

Answer 3

C

Question 4

Which of the following would be an example of vertical transmission of infectious agents?

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 5

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

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

Question 6

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

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

Question 7

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 8

Consider two isolates A and B: microbe A had a LD₅₀ of 5 * 10⁴, while microbe B recorded a 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 since they killed the animals
E) the values indicate that neither one is virulent

Question 9

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 10

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 11

Pathogenicity islands include all of the following EXCEPT:

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

Question 12

Type III and type I pili:

A) are similar to type IV in mode of secretion
B) are both mannose-resistant
C) both have an assembly that involves the secA general secretory pathway
D) are encoded by a pathogenicity island
E) are exclusively used for pathogenesis

Question 13

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

Question 14

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 15

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 16

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 17

What do yellow fever and West Nile virus have in common?

A) both cause cancer
B) birds are the reservoir for both viruses
C) both are close relatives of herpes virus
D) both are diarrheagenic viruses
E) both are flaviviruses

Question 18

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 19

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

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

Question 20

The toxin gene in Corynebacterium diphtheriae is located on:

A) plasmid
B) mobile genes called transposons
C) bacterial chromosomes
D) lysogenic phage genomes
E) all of the above

Question 21

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 22

Binding of which 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 23

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 24

Protein A helps Staphylococcus aureus avoid:

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

Question 25

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 26

Toxins with ADP ribosyltransferase activity cause which of the following?

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 27

Petechiae, which result from large amounts of endotoxin, are recognized from which of the following symptoms?

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

Question 28

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 29

Which of the following causes whooping cough?

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

Question 30

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 31

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 32

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 33

Which of the following is an example of an intracellular bacterial pathogen?

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

Question 34

What is a possible role for quorum sensing in pathogenicity?

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

Question 35

The enterotoxigenic Escherichia coli heat-labile toxin does which of the following?

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

Question 36

What do the anthrax, Escherichia coli, cholera, and Bordetella toxins have in common?

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

Question 37

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 38

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 39

Thick polysaccharide capsules are important virulence assets for which bacteria?

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 40

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) all of the above

Question 41

Commensals do not need virulence factors to survive on their host because:

A) they are well adapted for their specific niche
B) they do not breach the host barriers and immune system
C) they are recognized as self by the host
D) A and B only
E) all of the above

Question 42

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

Question 43

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

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

Question 44

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

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

Question 45

Bacteria whose optimum growth temperature is 37°C and that produce copious amounts of polysaccharides and capsules are most likely to be:

A) opportunistic pathogen
B) etiologic agent for septicemia
C) normal flora
D) marine organisms
E) probionts

Question 46

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

Question 47

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 48

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

Question 49

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

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

Helicobacter pylori survives in stomach acid due to what gene product?

A) type IV pilus
B) intimin
C) DNase
D) E3 ligase
E) urease

Question 52

Define a fomite and give at least two specific examples.

Question 53

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 54

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 55

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 56

State several of the characteristics pertaining to pathogenicity islands that suggest they are remnants of transposition.

Question 57

Descibe two specific nonpili protein adhesins used in pathogenesis.

Question 58

Which of the following is correct about Salmonella and Shigella?

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

Question 59

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 60

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 why knowing the type of binding is important in pathogenesis.

Question 61

Cholera toxin, produced by Vibrio cholerae, deregulates host cell adenylate cyclase activity. How is this accomplished?

Question 62

Describe why a blood agar plate can be used to detect the alpha-hemolytic activity of Staphylococcus aureus.

Question 63

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

Question 64

What are the subunits of the Bacillus anthracis plasmid-encoded toxin? Why is the edema factor (EF) and lethal factor (LF) alone nontoxic to the host?.

Question 65

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

Question 66

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 67

There is no host cell receptor for the enteropathogenic Escherichia coli intimin adhesion. Describe how this pathogen successfully colonizes human intestines.

Question 68

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

Question 69

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

Question 70

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