Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
Which of the following statements about M protein is FALSE?
1)
A)
It is a protein.
B)
It is heat– and acid–resistant.
C)
It is readily digested by phagocytes.
D)
It is found on Streptococcus pyogenes.
E)
It is found on fimbriae.
2)
The most frequently used portal of entry for pathogens is the
2)
A)
skin.
B)
parenteral route.
C)
mucous membranes of the respiratory tract.
D)
mucous membranes of the gastrointestinal tract.
E)
All of these portals are used equally.
3)
Bacteria that cause periodontal disease have adhesins for receptors on streptococci that colonize on
teeth. This indicates that
3)
A)
streptococcal colonization is necessary for periodontal disease.
B)
streptococci get bacterial infections.
C)
streptococci cause periodontal disease.
D)
bacteria that cause periodontal disease adhere to gums and teeth.
E)
bacteria that cause periodontal disease adhere to teeth.
Explanation:
4)
Which of the following statements about staphylococcal enterotoxin is FALSE?
4)
A)
It is a superantigen.
B)
It is produced by Staphylococcus aureus growing in the host’s intestines.
C)
It is an exotoxin.
D)
It causes diarrhea.
E)
It causes vomiting.
5)
All of the following contribute to a pathogen’s invasiveness EXCEPT
5)
A)
coagulases.
B)
hyaluronidase.
C)
capsules.
D)
cell wall components.
E)
toxins.
E
6)
Gram–negative septic shock results from the following events. What is the second step?
6)
A)
LPS is released from gram–negative bacteria.
B)
Phagocytes ingest gram–negative bacteria.
C)
IL–1 is released.
D)
Body temperature is reset in the hypothalamus.
E)
Fever occurs.
A
7)
The ability of some microbes, such as Trypanosoma or Giardia to alter their surface molecules and
evade destruction by the host’s antibodies is called
7)
A)
cytocidal effect.
B)
antigenic variation.
C)
lysogenic conversion.
D)
cytopathic effect.
E)
virulence.
B
B
8)
Injectable drugs are tested for endotoxins by
8)
A)
filtering out the cells.
B)
looking for turbidity.
C)
culturing bacteria.
D)
counting the viable bacteria.
E)
the Limulus amoebocyte lysate test.
9)
Which of the following contributes to the virulence of a pathogen?
9)
A)
toxin production
B)
evasion of host defenses
C)
numbers of microorganisms that gain access to a host
D)
numbers of microorganisms that gain access to a host and evasion of host defenses
E)
numbers of microorganisms that gain access to a host, evasion of host defenses, and toxin
production
10)
Which of the following cytopathic effects is cytocidal?
10)
A)
antigenic changes
B)
release of enzymes from lysosomes
C)
giant cells
D)
transformation
E)
inclusion bodies
11)
Antibiotics can lead to septic shock if used to treat
11)
A)
helminth infestations.
B)
gram–negative bacterial infections.
C)
protozoan infections.
D)
viral infections.
E)
gram–positive bacterial infections.
12)
Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by
12)
A)
conjugation.
B)
infecting a pathogenic Vibrio cholerae.
C)
transduction.
D)
transformation.
E)
phagocytosis.
13)
Which of the following statements about exotoxins is generally FALSE?
13)
A)
They are resistant to heat.
B)
They are produced by gram–positive bacteria.
C)
They are composed of proteins.
D)
They are more potent than endotoxins.
E)
They have specific methods of action.
A
14)
All of the following are methods of avoiding host antibodies EXCEPT
14)
A)
antigenic changes.
B)
membrane–disrupting toxins.
C)
IgA proteases.
D)
invasins.
E)
inducing endocytosis.
B
15)
Endotoxins are
15)
A)
excreted from the cell.
B)
associated with gram–positive bacteria.
C)
molecules that bind nerve cells.
D)
part of the gram–negative cell wall.
E)
A–B toxins.
D
C
Explanation:
16)
Which of the following does NOT contribute to the symptoms of a fungal disease?
16)
A)
toxins
B)
allergic response of the host
C)
capsules
D)
cell walls
E)
metabolic products
17)
The ID50 is
17)
A)
the dose that will kill 50 percent of the test population.
B)
the dose that will cause an infection in some of the test population.
C)
the dose that will kill some of the test population.
D)
the dose that will cause an infection in 50 percent of the test population.
E)
a measure of pathogenicity.
18)
Superantigens produce intense immune responses by stimulating lymphocytes to produce
18)
A)
exotoxins.
B)
leukocidins.
C)
cytokines.
D)
endotoxins.
E)
interferons.
19)
Which of the following statements is FALSE?
19)
A)
Coagulase destroys blood clots.
B)
Kinase destroys fibrin clots.
C)
Hyaluronidase breaks down substances between cells.
D)
Leukocidins destroy neutrophils.
E)
Hemolysins lyse red blood cells.
20)
Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages
20)
A)
carry plasmids.
B)
kill human cells.
C)
produce toxins.
D)
give new gene sequences to the host bacteria.
E)
kill the bacteria, causing release of endotoxins.
21)
Polio is transmitted by ingestion of water contaminated with feces containing polio virus. What
portal of entry does polio virus use?
21)
A)
skin only
B)
parenteral only
C)
mucous membranes only
D)
skin and parenteral
E)
skin, parenteral, and mucous membranes
22)
Endotoxins in sterile injectable drugs could cause
22)
A)
septic shock symptoms.
B)
nerve damage.
C)
giant cell formation.
D)
infection.
E)
no damage, because they are sterile.
23)
Cholera toxin polypeptide A binds to surface gangliosides on target cells. If the gangliosides were
removed,
23)
A)
polypeptide A would bind to target cells.
B)
polypeptide B would not be able to enter the cells.
C)
polypeptide A would enter the cells.
D)
Vibrio would bind to target cells.
E)
Vibrio would not produce cholera toxin.
Table 15.2
Bacterium ID50
E. coli O157:H7 20
Legionella pneumophila 1
Shigella 10
Treponema pallidum 57
24)
Which organism in Table 15.2 causes the most severe disease?
24)
A)
Shigella
B)
E. coli O157:H7
C)
Legionella pneumophila
D)
Treponema pallidum
E)
It cannot be determined from the information provided.
E
25)
All of the following are examples of entry via the parenteral route EXCEPT
25)
A)
bite.
B)
hair follicle.
C)
surgery.
D)
injection.
E)
skin cut.
B
B
26)
Which of the following is an example of direct damage due to bacterial infection?
26)
A)
the hemolysis of red blood cells in a staphylococcal infection
B)
the invasion and lysis of intestinal cells by E. coli
C)
the fever, nausea, and low blood pressure in a Salmonella infection
D)
the excessive secretion of fluids in a Vibrio cholera infection
E)
the uncontrolled muscle contractions in Clostridium tetani infection
27)
Bacteria such as E. coli and Salmonella produce invasins that bind host cells, thus causing the cells to
27)
A)
engulf the bacteria.
B)
release TNF.
C)
release cytokines.
D)
produce iron–binding proteins.
E)
destroy the bacteria.
A
28)
Botulism is caused by ingestion of a proteinaceous exotoxin; therefore, it can easily be prevented by
28)
A)
filtering food.
B)
administering antibiotics to patients.
C)
not eating canned food.
D)
boiling food prior to consumption.
E)
preventing fecal contamination of food.
D
29)
All of the following are used by bacteria to attach to host cells EXCEPT
29)
A)
ligands.
B)
capsules.
C)
M protein.
D)
A–B toxins.
E)
fimbriae.
D
B
30)
The fimbriae of Neisseria gonorrhea and enteropathogenic E. coli are examples of
30)
A)
adhesins.
B)
receptors.
C)
ligands.
D)
adhesins and ligands.
E)
adhesins, ligands, and receptors.
Table 15.1
Bacterium Portal of Entry ID50
Staphylococcus aureus Wound <10
Staphylococcus aureus Wound + Ampicillin 300
31)
Table 15.1 shows the ID50 for Staphylococcus aureus in wounds with and without the administration
of ampicillin before surgery. Based on the data, the administration of ampicillin before surgery
31)
A)
increases the risk of staphylococcal infection.
B)
decreases the risk of staphylococcal infection.
C)
replaces tetracycline.
D)
has no effect on risk of infection.
E)
The answer cannot be determined based on the information provided.
B
32)
Which of the following mechanisms is used by gram–negative bacteria to cross the blood–brain
barrier?
32)
A)
inducing TNF
B)
antigenic variation
C)
producing fimbriae
D)
producing toxins
E)
inducing endocytosis
A
D
Explanation:
33)
Which of the following is NOT a membrane–disrupting toxin?
33)
A)
A–B toxin
B)
streptolysin O
C)
leukocidin
D)
hemolysin
E)
streptolysin S
Table 15.2
Bacterium ID50
E. coli O157:H7 20
Legionella pneumophila 1
Shigella 10
Treponema pallidum 57
34)
Which organism in Table 15.2 most easily causes an infection?
34)
A)
Shigella
B)
E. coli O157:H7
C)
Treponema pallidum
D)
Legionella pneumophila
E)
The answer cannot be determined based on the information provided.
D
35)
Siderophores are bacterial proteins that compete with the host’s
35)
A)
antibodies.
B)
receptors.
C)
red blood cells.
D)
white blood cells.
E)
iron–transport proteins.
E
A
36)
Twenty–five people developed symptoms of nausea, vomiting, and diarrhea three to six hours after
attending a church picnic where they ate a ham and green bean casserole with cream sauce. The
most likely cause of this case of food intoxication is
36)
A)
cholera toxin.
B)
staphylococcal enterotoxin.
C)
botulinum toxin.
D)
erythrogenic toxin.
E)
aflatoxin.
37)
Cytopathic effects are changes in host cells due to
37)
A)
protozoan infections.
B)
fungal infections.
C)
helminthic infections.
D)
viral infections.
E)
bacterial infections.
38)
In response to the presence of endotoxin, phagocytes secrete tumor necrosis factor. This causes
38)
A)
a decrease in blood pressure.
B)
a aram–negative infection.
C)
an increase in red blood cells.
D)
the disease to subside.
E)
a fever.
39)
Symptoms of protozoan and helminthic diseases are due to
39)
A)
tissue damage due to growth of the parasite on the tissues.
B)
waste products excreted by the parasite.
C)
products released from damaged tissues.
D)
tissue damage due to growth of the parasite on the tissues and waste products excreted by the
parasite.
E)
tissue damage due to growth of the parasite on the tissues, waste products excreted by the
parasite, and products released from damaged tissues.
40)
Symptoms of intense inflammation and shock occur in some gram–positive bacterial infections due
to
40)
A)
lipid A.
B)
membrane–disrupting toxins.
C)
A–B toxins.
D)
superantigens.
E)
erythrogenic toxin.
D
41)
Patients developed inflammation a few hours following eye surgery. Instruments and solutions
were sterile, and the Limulus assay was positive. The patients’ inflammation was due to
41)
A)
bacterial infection.
B)
exotoxin.
C)
viral infection.
D)
endotoxin.
E)
The answer cannot be determined based on the information provided.
D
E
42)
Most pathogens that gain access through the skin
42)
A)
must be injected.
B)
must adhere first while their invasive factors allow them to penetrate.
C)
enter through hair follicles and sweat ducts.
D)
just infect the skin itself.
E)
can penetrate intact skin.
43)
Which of the following is NOT a cytopathic effect of viruses?
43)
A)
host cells fusing to form multinucleated syncytia
B)
increased cell growth
C)
inclusion bodies forming in the cytoplasm or nucleus
D)
toxin production
E)
cell death
44)
All of the following organisms produce exotoxins EXCEPT
44)
A)
Corynebacterium diphtheriae.
B)
Salmonella typhi.
C)
Staphylococcus aureus.
D)
Clostridium botulinum.
E)
Clostridium tetani.
45)
All of the following bacteria release endotoxin EXCEPT
45)
A)
Haemophilus influenzae.
B)
Clostridium botulinum.
C)
Proteus vulgaris.
D)
Salmonella typhi.
E)
Neisseria meningitidis.
TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false.
46)
The M protein enhances the virulence of Streptococcus by preventing phagocytosis.
46)
47)
In A–B exotoxins, the A component binds to the host cell receptor so that the B component can
enter the cell.
47)
48)
Ergot and aflatoxin are toxins sometimes found in grains contaminated with fungi.
48)
49)
Biofilms provide pathogens with an adhesion mechanism and aid in resistance to antimicrobial
agents.
49)
50)
The Limulus amoebocyte assay is used to detect minute amounts of endotoxin in drugs and
medical devices.
50)
51)
Most symptoms of endotoxins can be treated with administration of anti–endotoxin antibodies.
51)
52)
In general, the LD50 for exotoxins is much greater than the LD50 for endotoxins.
52)
53)
Cytopathic effects, such as inclusion bodies and syncytium formation, are the visible signs of viral
infections.
53)
54)
Infections with some viruses may induce chromosomal changes that alter the growth properties of
host cells.
54)
55)
Many pathogens use the same portal for entry and exit from the body.
55)
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
56)
Compare and contrast endotoxins and exotoxins. Why are exotoxins more potent than endotoxins?
57)
Some pathogens evade phagocytosis, while other pathogens evade host defenses by entering host cells. Discuss
the advantages and disadvantages of both of these evasion strategies.
58)
Antibiotics can kill gram–negative bacteria, but symptoms of fever and low blood pressure can persist. Why?
Answer Key
Testname: C15
Answer Key
Testname: C15