MCB4403 Exam 4 with 100% correct
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The pathogenic strain of Escherichia coli, E. coli O104:H4, expresses the Shiga
toxin and is highly resistant to many antibiotics. How did the E. coli O104:H4 strain
originally obtain the genes for the Shiga toxin and antibiotic resistance? - correct
answer ✔✔horizontal gene transfer
What bacterial chromosomal structure is represented in the figure below? -
correct answer ✔✔pathogenicity island
What do the following infections have in common: periodontitis, recurrent
tonsillitis, chronic otitis media, and osteomyelitis? - correct answer ✔✔They are
caused by bacterial biofilms
Endotoxins and exotoxins are both bacterial virulence factors that can affect the
infected host. Sort the following descriptions as to whether they apply to
endotoxins, exotoxins, or both. - correct answer ✔✔Endotoxins: released by dead
cells, harm the host by overstimulating the host's immune defense, component of
lipolysaccharide
Exotoxins: secreted by living cells, composed of protein, include hemolysis,
produced by gram+ bacteria
Both: are virulence factors, produced by gram- bacteria
,There are nine different functional categories of exotoxins. Match each of the five
exotoxins with its category - correct answer ✔✔Cytoskeleton: Vibrio cholera RTX
toxin depolymerizes actin
Cell Cycle: E. coli cytolethal distending toxin (CLDT) interrupts host cell division
Cell-Cell Adherence: S. aureus toxin breaks the connections between the dermis
and the epidermis
Vesicle Traffic: Hericobacter pylori VacA toxin causes vacuolization with the host
cell
Exocytosis: tetanus toxin prevents the release of the inhibitory neurotransmitter
gamma-aminobutyric acid (GABA)
The cholera toxin, an AB exotoxin, attaches an ADP-ribose group to the host's
stimulatory G factor (Gs). The normal function of Gs is to stimulate the host's
adenylate cyclase, which produces the second messenger molecule cAMP. This
toxin-mediated ADP-ribosylation of Gs has what effect? - correct answer
✔✔constant activation of Gs, causing an increase in cAMP levels and resulting in
increased ion transport from the infected host cell
The cholera toxin, an AB exotoxin, creates a(an) ____________ environment in
the intestinal lumen when compared to the cytoplasm of the intestinal cells -
correct answer ✔✔hypertonic
Sort the type III secretion system characteristics used by E. coli, S. enterica, or
both - correct answer ✔✔E. coli: allows the bacteria to avoid engulfment by host
cells, results in the tight binding between the bacteria and the host cell required
for pathogenesis, leads to the formation of a membrane pedestal on the surface
of the host cell
,S. enterica: results in engulfment of the bacteria by the host cell, prevents the
fusion of the phagosome and the lysosome
Both: results in the reorganization of the host cell cytoskeleton, genes for the
secretion system are found on pathogenicity islands within the bacterial genome
What are the advantages for EPEC, EHEC, and S. enterica of using the type III
secretion systems as opposed to type II secretion systems? - correct answer
✔✔The type III secretion systems avoid the need for a host cell receptor for the
effector or toxin
The type III secretion systems prevent dilution of the secreted effector or toxin
Primary pathogen, opportunistic pathogen, and reservoirs are terms used to
describe infections and infection cycles. Sort the descriptions to the correct term -
correct answer ✔✔Primary pathogen: can breach the healthy host's defenses,
Yersinia pestis can survive in macrophages bc it prevents lysosome/phagosome
fusion in macrophages
Opportunistic pathogen: requires a compromised host, S. aureus can infect
wounds in surgery patients
Reservoir: harbors the infectious microbe, includes birds for the eastern equine
encephalitis virus
A pathogenic bacterium has a low lethal dose 50% (LD50). What is true about the
bacteria? - correct answer ✔✔only a few of the bacteria are required to kill 50%
of infected hosts
Mycobacterium tuberculosis infects the lungs and can spread to other organs
from the lungs. When an infected individual coughs, the bacteria can enter the air
and infect nearby individuals.
, The mode of transmission for the M. tuberculosis pathogen is the ________
_________route.
The portal of entry for M. tuberculosis is ___________ - correct answer ✔✔direct
airborne, respiratory
Typhoid Mary was a professional cook at the turn of the twentieth century who
was an asymptomatic carrier of the bacteria Salmonella Typhi. She infected many
people who ate at the eating establishments where she worked through
contaminated food.
The mode of transmission for the S. Typhi pathogen is the ___________
__________ route.
The portal of entry for S. Typhi is _________ - correct answer ✔✔indirect vehicle,
oral
Lyme disease is caused by the bacteria Borrelia burgdorferi, which is transmitted
through the bite of a tick.
The mode of transmission for the B. burgdorferi pathogen is the __________
_________ route.
The portal of entry for B. burgdorferi is ____________ - correct answer
✔✔indirect vector, parenteral
The outer membrane of Gram-negative bacteria contains lipopolysaccharide (LPS).
When the Gram-negative bacterium dies, it releases LPS, which activates an
immune reaction. The immune reaction can cause symptoms ranging from fever
to shock to death. Because of the severe immune reaction elicited by free LPS, it is
called an endotoxin. The effects caused by endotoxin are known as what? - correct
answer ✔✔immunopathogenesis
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The pathogenic strain of Escherichia coli, E. coli O104:H4, expresses the Shiga
toxin and is highly resistant to many antibiotics. How did the E. coli O104:H4 strain
originally obtain the genes for the Shiga toxin and antibiotic resistance? - correct
answer ✔✔horizontal gene transfer
What bacterial chromosomal structure is represented in the figure below? -
correct answer ✔✔pathogenicity island
What do the following infections have in common: periodontitis, recurrent
tonsillitis, chronic otitis media, and osteomyelitis? - correct answer ✔✔They are
caused by bacterial biofilms
Endotoxins and exotoxins are both bacterial virulence factors that can affect the
infected host. Sort the following descriptions as to whether they apply to
endotoxins, exotoxins, or both. - correct answer ✔✔Endotoxins: released by dead
cells, harm the host by overstimulating the host's immune defense, component of
lipolysaccharide
Exotoxins: secreted by living cells, composed of protein, include hemolysis,
produced by gram+ bacteria
Both: are virulence factors, produced by gram- bacteria
,There are nine different functional categories of exotoxins. Match each of the five
exotoxins with its category - correct answer ✔✔Cytoskeleton: Vibrio cholera RTX
toxin depolymerizes actin
Cell Cycle: E. coli cytolethal distending toxin (CLDT) interrupts host cell division
Cell-Cell Adherence: S. aureus toxin breaks the connections between the dermis
and the epidermis
Vesicle Traffic: Hericobacter pylori VacA toxin causes vacuolization with the host
cell
Exocytosis: tetanus toxin prevents the release of the inhibitory neurotransmitter
gamma-aminobutyric acid (GABA)
The cholera toxin, an AB exotoxin, attaches an ADP-ribose group to the host's
stimulatory G factor (Gs). The normal function of Gs is to stimulate the host's
adenylate cyclase, which produces the second messenger molecule cAMP. This
toxin-mediated ADP-ribosylation of Gs has what effect? - correct answer
✔✔constant activation of Gs, causing an increase in cAMP levels and resulting in
increased ion transport from the infected host cell
The cholera toxin, an AB exotoxin, creates a(an) ____________ environment in
the intestinal lumen when compared to the cytoplasm of the intestinal cells -
correct answer ✔✔hypertonic
Sort the type III secretion system characteristics used by E. coli, S. enterica, or
both - correct answer ✔✔E. coli: allows the bacteria to avoid engulfment by host
cells, results in the tight binding between the bacteria and the host cell required
for pathogenesis, leads to the formation of a membrane pedestal on the surface
of the host cell
,S. enterica: results in engulfment of the bacteria by the host cell, prevents the
fusion of the phagosome and the lysosome
Both: results in the reorganization of the host cell cytoskeleton, genes for the
secretion system are found on pathogenicity islands within the bacterial genome
What are the advantages for EPEC, EHEC, and S. enterica of using the type III
secretion systems as opposed to type II secretion systems? - correct answer
✔✔The type III secretion systems avoid the need for a host cell receptor for the
effector or toxin
The type III secretion systems prevent dilution of the secreted effector or toxin
Primary pathogen, opportunistic pathogen, and reservoirs are terms used to
describe infections and infection cycles. Sort the descriptions to the correct term -
correct answer ✔✔Primary pathogen: can breach the healthy host's defenses,
Yersinia pestis can survive in macrophages bc it prevents lysosome/phagosome
fusion in macrophages
Opportunistic pathogen: requires a compromised host, S. aureus can infect
wounds in surgery patients
Reservoir: harbors the infectious microbe, includes birds for the eastern equine
encephalitis virus
A pathogenic bacterium has a low lethal dose 50% (LD50). What is true about the
bacteria? - correct answer ✔✔only a few of the bacteria are required to kill 50%
of infected hosts
Mycobacterium tuberculosis infects the lungs and can spread to other organs
from the lungs. When an infected individual coughs, the bacteria can enter the air
and infect nearby individuals.
, The mode of transmission for the M. tuberculosis pathogen is the ________
_________route.
The portal of entry for M. tuberculosis is ___________ - correct answer ✔✔direct
airborne, respiratory
Typhoid Mary was a professional cook at the turn of the twentieth century who
was an asymptomatic carrier of the bacteria Salmonella Typhi. She infected many
people who ate at the eating establishments where she worked through
contaminated food.
The mode of transmission for the S. Typhi pathogen is the ___________
__________ route.
The portal of entry for S. Typhi is _________ - correct answer ✔✔indirect vehicle,
oral
Lyme disease is caused by the bacteria Borrelia burgdorferi, which is transmitted
through the bite of a tick.
The mode of transmission for the B. burgdorferi pathogen is the __________
_________ route.
The portal of entry for B. burgdorferi is ____________ - correct answer
✔✔indirect vector, parenteral
The outer membrane of Gram-negative bacteria contains lipopolysaccharide (LPS).
When the Gram-negative bacterium dies, it releases LPS, which activates an
immune reaction. The immune reaction can cause symptoms ranging from fever
to shock to death. Because of the severe immune reaction elicited by free LPS, it is
called an endotoxin. The effects caused by endotoxin are known as what? - correct
answer ✔✔immunopathogenesis
