Deck 25: Microbial Pathogenesis

Question 1

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

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

Answer 1

B

Question 2

Type III and type I pili:

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

Answer 2

C

Question 3

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) cannot tell with information provided
B) microbe A
C) microbe B
D) equally virulent since they killed the animals
E) the values indicate that neither one is virulent

Answer 3

B

Question 4

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

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

Question 5

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 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.

Question 6

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 7

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 biofilm-producing strain
D) a piliated slow -growing Gram negative
E) a halophilic psychrophile

Question 8

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

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

Question 9

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 both flaviviruses

Question 10

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 11

Exotoxins:

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

Question 12

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 13

Which of the following are also known as frank pathogens?

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

Question 14

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

A) inhibit of protein synthesis
B) possess ADP ribisytransferase activity
C) cause diarrhea
D) disrupt cell membrane
E) trigger apoptosis

Question 15

Which of the following causes whooping cough?

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

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

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 18

Distinguishing features of a pathogenicity island include all of the following EXCEPT:

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

Question 19

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

A) Protein export systems are used to deliver subunits to the outside.
B) Chaperons are not needed for protein transport.
C) There is no periplasmic stopover.
D) Flagellar and pili proteins are added to the base of the structure.
E) Flagellar and pili proteins are added to the tip of the structure.

Question 20

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 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 21

Toxins with ADP ribosyltransferase activity cause which of the following results?

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 22

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

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

Question 23

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 24

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

A) Clostridium perfringens
B) Corynebacterium diphtheriae
C) Escherichia coli
D) Staphylococcus aureus
E) Bacillus anthracis

Question 25

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 26

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) that it was an obligate intracellular pathogen
C) it needed a helper virus to grow
D) that it needed high levels of iron
E) that it is a virus that needed cell culture

Question 27

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 28

The enterotoxigenic E. coli heat-stable toxin does which of the following?

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

Question 29

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 30

In signature-tagged mutagenesis, the tag is:

A) a lacZ gene
B) a fluorescent dye
C) an antibiotic-resistance gene
D) an oligonucleotide
E) a PCR primer sequence

Question 31

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) two of the above are correct
E) all of the above

Question 32

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 33

Urease is a virulence factor produced by:

A) uropathogenic E. coli
B) Vibrio cholerae
C) Bordetella pertussis
D) Helicobacter pylori
E) Pseudomonas aeruginosa

Question 34

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

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

Question 35

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 36

Antigenic shifts and phase variants are important virulence assets for which bacteria?

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

Question 37

The cholera and E. coli (traveler's diarrhea) toxins __________, leading to high levels of cAMP in the cell.

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

Question 38

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

A) its nutritional requirements
B) the virulence factors employed in pathogenesis
C) infectious and lethal doses
D) mechanisms of disease
E) tissue tropism and disease progression

Question 39

Which of the following techniques will 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 40

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 the gastric acid kill
D) the intestine has many receptors for the toxin
E) it secretes a superantigen

Question 41

There was a dramatic dip in life expectancy in the United States in 1918 due to an epidemic of:

A) cholera
B) plague
C) polio
D) influenza
E) typhoid fever

Question 42

Protein A helps Staphylococcus aureus avoid :

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

Question 43

Which is an example of an intracellular bacterial pathogen?

A) HIV
B) Streptococcus mutans
C) Coxiella burnetii
D) Neisseria gonorrhoeae
E) Bacillus anthracis

Question 44

What is a possible role for quorum sensing in pathogencity?

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 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.

Question 46

Which of the following HIV proteins down-regulates cell surface CD4 and MHC class I?

A) Tat
B) Vpr
C) Nef
D) Vif
E) Vpu

Question 47

HPV strains that cause cervical cancer produce protein E7, which:

A) causes the degradation of pRb
B) frees up the transcription factor E2F to express the oncogene
C) ADP ribosylates protein synthesis factor EF2
D) activates G proteins
E) down-regulates MHC proteins on the cell surface

Question 48

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

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

Question 49

The number of microbes that kill half the experimental animals is called the LD₅₀ dose. What is the relationship between this measure and microbial virulence?

Question 50

Define a fomite and give at least two examples.

Question 51

Briefly describe three classic modes of action of bacterial toxins.

Question 52

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 one infectious disease.

Question 53

HPV strains that cause cervical cancer produce protein E7, which:

A) causes the degradation of pRb
B) frees up the transcription factor E2F to express the oncogen
C) ADP ribosylates protein synthesis factor EF2
D) activates G proteins
E) down-regulates MHC proteins on the cell surface

Question 54

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

Question 55

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

Question 56

Which of the following is correct about Salmonella and Shigella?

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

Question 57

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

Question 58

During the latent stage of herpes virus infection:

A) host cells rapidly undergo apoptosis causing cold sores
B) the viral genome exists as a plasmid in the cell
C) apoptosis is inhibited by small RNA encoded by virus
D) cold sores are common
E) the host is highly infectious

Question 59

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

Question 60

Mention two nonpili protein adhesins used in pathogenesis.

Question 61

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

Question 62

The host species can evolve to become resistant to virus infection when the gene encoding the receptor mutates. Explain.

Question 63

Some bacterial pathogens develop a latent stage in the host, where they are undetectable as a distinct entity but are still able to emerge and cause disease at certain times. Why doesn't the host eliminate such pathogens by apoptosis?

Question 64

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

Question 65

Compare and contrast the promoter trap plasmid technique and the signature-tagged mutagenesis technique.

Question 66

Describe the role of pRb in the regulation of cell division. How does the human papillomavirus deregulate cell division in infected cells?

Question 67

What are the subunits of the Bacillus anthracis, plasmid-encoded toxin? Why is the EF and LF nontoxic to the host?.

Question 68

Describe the mode of action of diphtheria toxin.

Question 69

Name and briefly describe the role of three of the five HIV proteins that affect pathogenesis.

Question 70

Describe the deregulation of adenylate cyclase activity by cholera toxin.