MOSBY MIcrobio and immunology

Question 1

1. Which inflammatory mediator is produced by B-cells
   and T-cells?
   A. Cytokines
   B. Immunoglobulins
   C. Interleukin-4
   D. Interleukin-6

Answer 1

ANS: A
Cytokines (A) are inflammatory mediators produced by
B-cells and T-cells. Immunoglobulins (B) are produced
by plasma cells, which are produced by B-lymphocytes.
Interleukin-4 (C) and interleukin-6 (D) are found in
T-cells and stimulate the B-lymphocyte response.

Question 2

2. Which is the predominant antibody in saliva?
   A. Immunoglobulin A
   B. Immunoglobulin E
   C. Immunoglobulin D
   D. Immunoglobulin G

Answer 2

ANS: A
Immunoglobulin A (A) is the predominant antibody
found in saliva and is termed the secretory antibody.
The other antibodies—immunoglobulin E (B),
immunoglobulin D (C), and immunoglobulin G (D)—
may be found in saliva but not in amounts as large as
that of immunoglobulin A.

Question 3

3. Which cells are most involved in cell-mediated
   immunity?
   A. Mast cells
   B. Plasma cells
   C. Neutrophils
   D. T-lymphocytes

Answer 3

ANS: D
T-lymphocytes (D) are responsible for cell-mediated
immunity. Mast cells (A) release histamine and
other vasoreactive mediators in allergic reactions,
and plasma cells (B) produce immunoglobulin G.
Neutrophils (C) are a type of white blood cells.

Question 4

4. Contact dermatitis is considered which type of
   hypersensitivity reaction?
   A. I
   B. II
   C. III
   D. IV

Answer 4

ANS: D
Contact dermatitis is considered a type IV
hypersensitivity reaction (D), involving a T-cell–mediated
response, not an antibody. Types I (A), II (B), and III (C)
are associated with the formation of antibodies.

Question 5

5. Saliva has each of these protective mechanisms
   EXCEPT one. Which one is the EXCEPTION?
   A. Increases in volume with increased inflammation
   B. Buffers the acids that are created by oral bacteria
   C. Contains secretory antibodies
   D. Lubricates mucosal tissues

Answer 5

ANS: A
Saliva does not increase (A) because of an increase
in inflammation. Buffering the acids created by oral
bacteria (B), containing secretory antibodies (C), and
lubricating mucosal tissues (D) are the protective
mechanisms of saliva.

Question 6

6. Which cellular characteristic describes why gram-positive
   bacteria stain differently from how gram-negative
   bacteria stain?
   A. Thinner peptidoglycan
   B. Thicker peptidoglycan
   C. Less cytoplasm
   D. More cytoplasm

Answer 6

ANS: B
The cell walls of gram-positive bacteria contain
a thicker layer of peptidoglycan (B) than those of gram-negative bacteria, absorbing more stain and thus
staining darker. Gram-negative bacterial cell walls
contain less peptidoglycan than those of gram-positive
bacteria (A), staining lighter. Cytoplasm amounts
(C, D) do not directly affect the staining capabilities of
bacteria.

Question 7

7. An ideal antibiotic has the ability to inhibit a wide range of
   microorganisms, including normal flora. It will only act on
   the pathogen, with no harmful effect to the human host.
   A. Both statements are true.
   B. Both statements are false.
   C. The first statement is true, and the second statement
   is false.
   D. The first statement is false, and the second
   statement is true.

Answer 7

ANS: D
The correct choice is (D). The first statement is false
as an ideal antibiotic should have the ability to inhibit
a wide range of microorganisms but NOT the normal
flora. The second statement is true. Choices A, B, and
C do not accurately reflect the statements.

Question 8

8. Which term BEST describes the ability of a
   microorganism to cause disease?
   A. Stability
   B. Virulence
   C. Productivity
   D. Transmissibility

Answer 8

ANS: B
A microorganism’s virulence (B) best describes its
ability to cause disease. Stability (A), productivity (C),
and transmissibility (D) do not directly influence the
ability of a microorganism to cause disease.

Question 9

9. The cellular structure that is used to classify a bacterial
   species as gram-positive or gram-negative is the
   A. flagellum.
   B. cell wall.
   C. cell membrane.
   D. pilus.
   E. glycocalyx

Answer 9

ANS: B
Differences between cell wall structure (B) and
composition classify bacterial species as grampositive or gram-negative. Gram-positive bacteria
contain a large amount of peptidoglycan in a
single, thick layer, whereas gram-negative bacteria
contain a thin layer of peptidoglycan sandwiched
between the cell membrane and an outer membrane
containing lipopolysaccharides. A flagellum (A) is
a hairlike structure that projects from the cell body
and aids in movement. A cell membrane (C) is the
outer covering of a cell. The pilus (D) is a hairlike
projection found on the surface of many bacteria.
Glycocalyx (E) is a glycoprotein–polysaccharide
covering that surrounds many cells. None of these
structures differentiates between gram-positive and
gram-negative cells.

Question 10

10. All are typical bacterial cell shapes EXCEPT one.
    Which one is the EXCEPTION?
    A. Spirochete
    B. Coccus
    C. Bacillus
    D. Disk

Answer 10

ANS: D
A disk (D) is not a shape typical of bacterial cells
viewed under the microscope. A spirochete (A) is a corkscrew-shaped bacterium. A coccus (B) is a
round-shaped bacterium. A bacillus (C) is a rod-shaped
bacterium.

Question 11

11. The prefix strepto- designates bacteria that take on
    which type of arrangement?
    A. Chain
    B. Tetrad
    C. Cluster
    D. Sarcina
    E. Diploid

Answer 11

ANS: A
The prefix strepto- is the designation for bacterial
cells arranged in a chainlike fashion (A). Two
common examples are streptococci and streptobacilli.
Tetrad (B) describes an arrangement of four cocci in
a square shape. The cluster arrangement (C) contains
cocci that are divided in numerous random planes.
Sarcina (D) designates a cubelike arrangement.
The diploid (E) arrangement consists of two joined
bacterial cells.

Question 12

12. Which is the MOST appropriate definition of a
    microorganism?
    A. An organism with individual cells that can be seen
    with the unaided eye
    B. An organism that does not contain a nucleus
    C. An organism with individual cells that are too small
    to be seen with the unaided eye
    D. An organism that does not contain a cell membrane.

Answer 12

ANS: C
A microorganism is an organism in which the
individual cells cannot be seen with the unaided eye
(C). A microscope must be used to view individual
microbial cells (A). Eukaryotic microorganisms do
contain a nucleus in their cells (B). All microbial cells
contain cell membranes (D

Question 13

13. The key to Alexander Fleming’s recognition of
    penicillin as a tool for fighting bacterial infections was
    his observation that
    A. bacteria inhibited the growth of nearby bacteria.
    B. mold inhibited the growth of nearby bacteria.
    C. mold inhibited the growth of nearby yeast.
    D. viruses could produce penicillin.

Answer 13

ANS: B
Alexander Fleming observed that the growth of
Staphylococcus aureus bacterial colonies were
inhibited on plates contaminated with the mold
Penicillium notatum (B), leading to the identification
of the antibacterial agent penicillin. Bacteria are not
inhibited by growth of nearby bacteria (A). Mold does
not inhibit the growth of nearby yeast (C). Viruses do
not produce penicillin (D).

Question 14

14. The best definition of a virus is

A. a eukaryotic microorganism with branching
hyphae.
B. an acellular microorganism that requires a host for
replication.
C. a eukaryotic microorganism with the ability for
locomotion.
D. a prokaryotic microorganism that may exist singly,
in pairs, chains, or clusters.
E. a photosynthetic cell classified by differences in
pigmentation

Answer 14

ANS: B
A virus is an acellular microorganism that requires
the nuclear materials of the host to replicate. Because
viruses are not composed of cells, they are referred to as
acellular; in addition, they do not contain the resources
needed for replication and so must use host cell resources
to complete their replication (B). A eukaryote is a cell
that contains complex structures, including a nucleus
bound within a membrane (A, C). Prokaryotic cells do
not have a nucleus, a nuclear membrane, or any other
membrane-bound organelles (D). A virus is not a
cell (E) and cannot be classified as either prokaryotic or
eukaryotic

Question 15

15. You are observing a cell through a microscope
    and note that it does not have a nucleus. From this
    observation, you can also conclude that it most likely
    A. has a cell wall containing peptidoglycan.
    B. is a fungi.
    C. moves with the aid of cilia.
    D. does not have a cell membrane

Answer 15

ANS: A
Prokaryotic cells (bacteria) have cell walls containing
peptidoglycan, and only prokaryotic cells do not
have a nucleus (A). Fungi are made up of eukaryotic
cells, which do contain a nucleus (B). Cilia are only
found on the surface of eukaryotic cells, which have a
nucleus (C). All cells, prokaryotic and eukaryotic, have
a cell membrane (D).

Question 15

16. Structures that enable the transfer of genetic material
    between bacterial cells are
    A. fimbriae.
    B. capsules.
    C. cilia.
    D. pili

Answer 15

ANS: D
The only structures in this list of choices that can
transfer genetic material are pili (D). Fimbriae (A)
allow for attachment to host cells. Capsules (B) are
protective structures around bacterial cells. Cilia (C)
allow for movement of protozoan cells.

Question 16

17. Observation of microbial cell arrangement can
    be used to differentiate between streptococci and
    staphylococci. Observation of microbial cell shape
    can be used to differentiate between streptococci and
    staphylococci.
    A. Both statements are true.
    B. Both statements are false.
    C. The first statement is true, and the second statement
    is false.
    D. The first statement is false, and the second
    statement is true.

Answer 16

ANS: C
The first statement is true, and the second is
false (C). The arrangements of streptococci and
staphylococci are different; streptococci are arranged
in a chainlike fashion, whereas staphylococci
are arranged in clusters. Both streptococci and
staphylococci have the same coccal, or round, shape.
Choices A, B and D do not correctly reflect the
statements.

Question 16

18. A patient is believed to be infected by Mycobacterium
    tuberculosis, the causative agent of tuberculosis.
    These microorganisms have a waxy cell wall. Which
    of the following staining methods can verify this
    assumption?
    A. Gram
    B. Flagellar
    C. Acid-fast
    D. Endospor

Answer 16

ANS: C
The standard stain for identifying bacteria from the
Mycobacterium genus, including Mycobacterium
tuberculosis, is the acid-fast stain (C). The components
of this stain allow for penetration of the characteristic
waxy cell walls of cells in this genus. Gram stain
(A) is used for staining of bacterial cell walls and
differentiation between gram-positive and gramnegative bacteria. The flagellar stain (B) is used to
identify bacteria containing a flagella. The endospore
(D) is used to differentiate between bacteria that form
endospores.

Question 17

19. Which type of microorganism is most likely to be
    found in the large intestine, where there is no exposure
    to oxygen?
    A. Obligate aerobe
    B. Obligate anaerobe
    C. Facultative anaerobe
    D. Airborne bacteria

Answer 17

ANS: B
Obligate anaerobes (B) can only be grown in the
absence of oxygen and are best suited for growth in an
area with limited or nonexistent exposure to oxygen.
Obligate aerobes (A) require oxygen to survive
and would not thrive in an area lacking in oxygen.
Facultative anaerobes (C) can grow in the presence or
absence of oxygen but favor growth in the presence
of oxygen, as it provides them with more energy.
Airborne bacteria (D), by their very nature, require
some oxygen.

Question 18

20. Which type of microorganism generally uses aerobic
    metabolism when oxygen is available but can carry
    on fermentation in an anaerobic environment when
    necessary?
    A. Aerotolerant anaerobes
    B. Facultative anaerobes
    C. Obligate anaerobes
    D. Obligate aerobes

Answer 18

ANS: B
Facultative anaerobes (B) can grow in the presence
or absence of oxygen, but they favor growth in the
presence of oxygen, as it yields them more energy;
therefore, they shift from anaerobic metabolism to
aerobic metabolism (growth in the presence of oxygen)
if oxygen is available. Aerotolerant (A) and obligate
(C) anaerobes favor growth in the absence of oxygen,
and obligate aerobes (D) can only grow in the presence
of oxygen

Question 19

21. All increase the virulence of bacteria EXCEPT one.
    Which one is the EXCEPTION?
    A. Exotoxins
    B. Bacterial glycocalyx
    C. Lipopolysaccharides
    D. Glycosaminoglycans

Answer 19

ANS: D
Glycosaminoglycans or mucopolysaccharides (D)
are long chains of sugar molecules found throughout
the body and are not linked to bacterial virulence.
Exotoxins (A) are toxins secreted by some bacteria that
can damage the host by destroying cells or disrupting
normal cellular function. The production of exotoxins
increases bacterial virulence. Some bacteria have
a glycoprotein–polysaccharide or glycocalyx (B)
covering that allows bacterial adherence and protects
the bacteria from phagocytosis, adding to bacterial
virulence. Lipopolysaccharides (C) or endotoxins
are a component of gram-negative cell walls that are
released when the cell is lysed and greatly add to
bacterial virulence

Question 20

22. Most human pathogens are classified as
    A. mesophiles.
    B. thermophiles.
    C. psychrophiles.
    D. hyperthermophiles.

Answer 20

ANS: A
Organisms classified as mesophiles (A) grow best at
human body temperature and are most likely to be human pathogens. Thermophiles (B), psychrophiles
(C), and hyperthermophiles (D) grow best at
temperatures lower or higher than that of human
body temperature; if they cannot grow at human body
temperature, they are unlikely to be human pathogens.

Question 20

23. Microbes that are classified as beta-hemolytic have the
    ability to
    A. lyse white blood cells.
    B. produce endotoxins.
    C. lyse red blood cells.
    D. ferment glucose

Answer 20

ANS: C
Microorganisms that are beta-hemolytic have the
ability to destroy or lyse red blood cells (C). Betahemolytic microbes cannot lyse white blood cells (A),
produce endotoxins (B), or ferment glucose (D).

Question 21

24. Which kind of relationship is exhibited by bacterial
    normal flora in a host’s large intestine?
    A. Commensal
    B. Parasitic
    C. Symbiotic
    D. Competitive

Answer 21

ANS: C
A symbiotic relationship (C) is a relationship in which
both partners benefit. Normal flora in the host’s large
intestine benefits by receiving nutrients and space
for survival; the host benefits because the normal
bacterial flora keeps pathogens from colonizing the
area, produces vitamins B and K, and aids digestion.
Commensalism (A) is a relationship in which one
partner benefits and the other is unaffected (neither
benefits nor is harmed) by the relationship. A parasitic
relationship (B) is a relationship in which one partner
benefits and the other is harmed. A competitive
relationship (D), or antagonistic relationship, occurs
when organisms are competing for a limited supply of
resources

Question 22

25. Antibiotics may lead to septic shock if used to treat
    A. viral infections.
    B. gram-positive bacteria that produce exotoxins.
    C. protozoan infections.
    D. helminth infestations.
    E. gram-negative bacteria that produce endotoxins.

Answer 22

ANS: E
Septic shock may occur if large amount of endotoxins
or lipopolysaccharides enter the bloodstream.
Endotoxins are produced by some species of gramnegative bacteria when the cells divide, lyse, or both
(E). Only gram-negative bacteria produce endotoxins;
viruses (A), protozoa (C), helminthes (D), and grampositive bacteria (B) cannot produce these toxins.

Question 23

26. A change in the location of normal flora may result in
    an opportunistic infection. Opportunistic infections
    contribute to nosocomial infections.
    A. Both statements are true.
    B. Both statements are false
    C. The first statement is true, and the second statement
    is false.
    D. The first statement is false, and the second
    statement is true.

Answer 23

ANS: A
Both statements are true (A). If normal flora changes
location from a region where it is normally found to
an area where it is either not normally found or an
area in which no bacteria should ever be found, it may
seize the opportunity to cause infection (opportunistic
infection). Many nosocomial infections (those acquired in a health care setting) are caused by bacteria that are
normally part of the host’s normal flora but that have
been given an opportunity to cause infection either
because they have gained access to an area of the body
where they are not normally found or because the
host’s immune system is suppressed. Choices B, C, and
D do not accurately reflect the statements.

Question 24

27. New viruses rarely cause disease, but if disease
    is produced, it is very severe. On the basis of this
    characteristic, the pathogenicity and virulence of a
    particular virus would be considered
    A. low, high.
    B. low, low.
    C. high, low.
    D. high, high

Answer 24

ANS: A
Choice A is correct, as it indicates low pathogenicity
and high virulence. Pathogenicity refers to the ability
of a microorganism to enter a host, infect the host,
and cause disease. Microorganisms may be classified
as having low or high pathogenicity, depending on
their ability to enter a host, infect the host, and cause
disease. Virulence refers to the severity of the disease
that a microorganism causes. Microorganisms may
also be classified as having low or high virulence,
depending on the severity of the disease that they
cause. In the question asked above, the virus does not
often cause disease; therefore, its pathogenicity would
be low. However, the disease caused by the virus
is severe, so its virulence would be high. Choice B
indicates low virulence, which is incorrect with regard
to the severity of the disease. Choice C indicates high
pathogenicity and low virulence, which is incorrect
because the virus does not often cause disease, which
indicates low pathogenicity, but the disease produced
is severe, which indicates high virulence. Choice D
indicates high pathogenicity, which is incorrect as the
virus described does not often cause disease.

Question 25

28. Convalescence is the disease stage in which the number
    of microorganisms causing the disease and the intensity
    of signs and symptoms decrease. During convalescence,
    the host is beginning to feel better, but the pathogen
    causing the disease may still be spread to others.
    A. Both statements are true.
    B. Both statements are false.
    C. The first statement is true, and the second statement
    is false.
    D. The first statement is false, and the second
    statement is true

Answer 25

ANS: A
Both statements are true (A). Within the four disease
stages—incubation, prodromal stage, acute stage,
and convalescence—convalescence is the fourth
stage. It is the period after the illness stage and is
characterized by a decrease in the number of diseasecausing microorganisms and therefore also a decrease
in the signs and symptoms associated with the disease.
Although a host is beginning to feel better during this
stage, he or she still harbors the pathogen and may still
spread it to others. In fact, a pathogen can be spread
during all disease stages. Choices B, C, and D do not
accurately reflect the statements.

Question 26

29. Which condition is a symptom of a disease?
    A. Fever
    B. Sore throat
    C. Vomiting
    D. High blood pressure

Answer 26

ANS: B
Symptoms are characteristics of a disease that cannot
be observed or measured. They differ from signs,
in which a disease characteristic can be observed,
measured, or both. The only choice that cannot be
observed or measured is a sore throat (B), which can
be felt by the individual but cannot be observed or
measured. Fever (A), vomiting (C), and high blood
pressure (D) can all be observed and measured.

Question 27

30. The virus that causes influenza is often transmitted
    over a distance less than 1 meter (m) by an
    unprotected sneeze. This is an example of what type of
    transmission?
    A. Vector
    B. Droplet
    C. Fomite
    D. Vehicle

Answer 27

ANS: B
Droplet transmission (B) is defined as transmission
of a microorganism in the air over a distance less
than 1 meter. Vector transmission (A) is transmission
by an arthropod such as a tick or a mosquito. Fomite
transmission (C) is indirect transmission through an
inanimate object such as a dental instrument. Vehicle
transmission (D) includes airborne transmission
(transmission through air over distances greater than
1 meter), foodborne transmission, and waterborne
transmission.

Question 28

31. The mucous membranes of the body are portals of
    entry for pathogens. Which mucous membranes are the
    MOST common site of entry for infectious agents?
    A. Oral cavity
    B. Genitourinary tract
    C. Gastrointestinal tract
    D. Respiratory tract

Answer 28

ANS: D
The mucous membranes of the respiratory tract (D)
are the most common site of entry for pathogenic
microorganisms. The mucous membranes of the oral
cavity (A), genitourinary (B) and gastrointestinal (C)
tracts, and skin are less frequently portals of entry for
human pathogens.

Question 29

32. Bacterial endospores or spores are a problem in
    sterilizing instruments and equipment because
    A. endospores can transform into a vegetative state.
    B. most pathogenic bacteria are spore-formers.
    C. spores are resistant to physical and chemical
    agents.
    D. spores are protected by a waxy coating

Answer 29

ANS: C
Endospores or spores are structures formed within
some species of gram-positive bacteria that can remain
dormant for years and are unusually resistant to heat,
drying, chemical disinfection, and radiation (C). The
ability to destroy spores is the difference between
disinfection and sterilization, and the use of live spore
testing is the definitive test for the effectiveness of
the sterilization process. Although, endospores can
transform back into a vegetative cell (A) through the
process of germination if conditions are favorable, this
is not the primary concern for dental professionals.
The ability to produce endospores is restricted to
the bacterial genera Bacillus and Clostridium (B).
Mycobacterium species have a waxy, protective
coating, not endospores (D).

Question 30

33. Which object is a fomite?
    A. Water
    B. Droplets from a sneeze
    C. Body fluids
    D. Insects
    E. Hypodermic needle

Answer 30

ANS: E
A fomite is an inanimate object such a hypodermic
needle (E) used in indirect-contact transmission
to spread a pathogen from one reservoir to the
next susceptible host. Water (A) is used in vehicle
transmission. Droplets from a sneeze (B) are involved
in droplet transmission. Bodily fluids (C) would be
involved in direct-contact spread if the next susceptible
host came into direct contact with this secretion from
the pathogen’s reservoir. Insects (D) are involved in
vector transmission.

Question 31

35. All are considered nonspecific body immune
    defenses EXCEPT one. Which one is the
    EXCEPTION?
    A. Antibodies
    B. Mucous membranes
    C. Intact skin
    D. Phagocytic cells
    E. Lysozyme in tears

Answer 31

ANS: A
Antibodies (A) are components of the body’s specific
immune system. They are produced by B-cells, which
must be stimulated or called into action to produce
plasma cells that produce antibodies. The antibodies
will then specifically target the pathogens that caused
their production in response. Mucous membranes (B),
intact skin (C), phagocytic cells such as neutrophils
and macrophages (D), and lysozyme in tears (E) are
components of the body’s nonspecific defenses that are
always present and ready to defend the body against
pathogens

Question 31

34. Interferons nonspecifically inhibit the spread of which
    type of infections?
    A. Viral
    B. Bacterial
    C. Protozoan
    D. Parasitic worm

Answer 31

ANS: A
Interferons are a part of the nonspecific, or first-line
bodily defense. Their release inhibits viral infection
(A) by activating the production of antiviral proteins
in cells, which will stop the spread of viral infection to
other host cells. Bacterial (B) and protozoal infections
(C) are primarily controlled through stimulation of
humoral immunity. Parasitic worm infestations (D)
are primarily controlled through stimulation of cellmediated immunity.

Question 32

36. T-helper cells produce
    A. antibodies.
    B. cytolytic enzymes.
    C. plasma cells.
    D. cytokines.

Answer 32

ANS: D
T-helper cells produce cytokines (D), which are
chemical messengers that activate other components
of the immune system. Antibodies (A) are produced by plasma cells, which are a product of B-lymphocytes.
Cytolytic enzymes (B) are produced by killer T-cells
and serve to lyse infected cells. Plasma cells (C) are
a product of B-lymphocytes and cannot be produced
by T-cells, although T-helper cells can send signals to
them to produce antibodies.

Question 33

37. Which is NOT a characteristic of adaptive immunity?
    A. Nonspecific
    B. Possesses memory
    C. Requires activation
    D. Represents third line of defense

Answer 33

ANS: A
“Nonspecific” is incorrect because adaptive
immune response is a specific immune response that
specifically targets the pathogen that stimulated it (A).
The remaining choices all define adaptive immunity.
Memory cells are generated so that the immune
system will remember a pathogen if it enters the body
again (B) and generate a quick response. This arm
of the immune system must be activated (C), usually
by components of the nonspecific or innate immune
system. Adaptive immunity is considered the third line
of the body’s defense (D)

Question 34

38. Antigens are
    A. cells that protect the body against invaders.
    B. enzymes secreted by white blood cells.
    C. molecules that the body specifically recognizes as
    foreign.
    D. proteins the body produces against invading substances.
    E. proteins on the surface of the cell which determine
    tissue type

Answer 34

ANS: C
Antigens are specific modules of a pathogen or
substances secreted by the pathogen that the body
recognizes as foreign (C). Cells that protect the
body against invaders include white blood cells and
antibodies (A). Enzymes secreted by white blood
cells include collagenase, lysozyme, and matrix
metalloproteinases (B). Complement proteins
are produced to protect the body against foreign
invaders (D). Proteins on the surface of cells that
code for tissue type and transplant compatibility
are called the major histocompatibility complex
(MHC) (E).

Question 35

39. An antibiotic binds to the 30S ribosomal subunit. On
    the basis of this information, this antibiotic inhibits
    which of the following processes?
    A. Transcription in eukaryotes
    B. Transcription in prokaryotes
    C. Translation in eukaryotes
    D. Translation in prokaryotes

Answer 35

ANS: D
Ribosomes are responsible for translation or protein
synthesis. Ribosomes in eukaryotes are composed
of a large 60S subunit and a small 40S subunit in
comparison with ribosomes in prokaryotes that are
composed of a large 50S subunit and a small 30S
subunit. Some antibiotics prevent protein synthesis
in bacteria, which are prokaryotes (D). Transcription
is the process by which messenger ribonucleic acid
(mRNA) is synthesized from a deoxyribonucleic acid
(DNA) template and is not part of the mechanism
of action for antibiotics (A, B). Protein synthesis in
eukaryotes (C) is not affected by antibiotics.

Question 36

40. A viral infection may be treated with an antibiotic.
    Antivirals are difficult to develop because viruses use
    host cell machinery for their replication.
    A. Both statements are true.
    B. Both statements are false.
    C. The first statement is true, and the second statement
    is false.
    D. The first statement is false, and the second
    statement is true.

Answer 36

ANS: D
The first statement is false, and the second
statement is true (D). Antibiotics are specific for
treating bacterial infections, whereas antivirals are
used for the treatment of viral infections. Viruses
do not contain the resources needed for replication,
so they use host cell nucleic acids to complete
their replication. This makes the development of
antivirals difficult because there are significantly
fewer antiviral targets. In addition, the necessity
of replication inside a host cell makes it difficult
to develop an antiviral that can target and destroy
the virus while leaving the host cell unaffected.
Choices A, B, and C do not accurately reflect the
statements.

Question 37

42. Standard methods of sterilization are NOT effective in
    destruction of
    A. viruses.
    B. bacteria.
    C. prions.
    D. protozoa.
    E. fungi.

Answer 37

ANS: C
Prions (C), or proteinaceous infectious particles, are
not destroyed by standard sterilization techniques.
Additional measures such as incineration are needed
to destroy prions. Standard sterilization methods can
destroy viruses (A), bacteria (B), protozoa (D), and
fungi (E).

Question 38

41. The BEST definition of sterilization is
    A. disinfection of living tissue.
    B. use of a chemical agent to destroy pathogens.
    C. killing or removal of all microorganisms in a
    material or an object.
    D. reduction in the number of pathogenic
    microorganisms in a material or an object

Answer 38

ANS: C
Sterilization is the removal or destruction of
all microorganisms, including endospores (C).
Disinfection of living tissue (A) describes the term
antisepsis. The use of a chemical agent to destroy
pathogens is termed disinfection (B). Not all
microorganisms are pathogens (D).

Question 39

43. A chemical agent that kills pathogenic microbes in
    general is a(n)
    A. sanitizer.
    B. germicide.
    C. disinfectant.
    D. fungicide.
    E. antiseptic.

Answer 39

ANS: B
A germicide (B) is capable of killing pathogenic
microbes in general. The suffix -cide indicates that
a particular agent has killing capability. A sanitizer
(A) does not kill all pathogenic microbes but
simply reduces them to a safe level. Disinfectants
(C) are applied to nonliving objects to destroy
microorganisms on surfaces. Fungicide (D) is a
chemical that specifically kills fungi. Antiseptics
(E) are substances that inhibit the growth and
development of microorganisms and are applied to
living tissues.

Question 40

44. Proper filtration of air and liquids relies on which
    property?
    A. Addition of pressure
    B. Sterile liquids
    C. Filter size
    D. Filter pore size

Answer 40

ANS: D
A filter used for the elimination of microbes in the
air or in liquid relies on the presence of pores of a
particular size to keep out, or filter out, microbes
(D). The application of pressure (A) would not
properly filter out air and liquids. Sterile liquids (B)
are produced following the filtration process. Filter
size (C) is irrelevant; it is the size of the pores in the
filters that determine what microbes can or cannot pass
through them.

Question 41

45. Which BEST describes the selective toxicity
    characteristic of antimicrobials?
    A. The ability to harm microbes without significantly
    harming host cells
    B. The ability to cause host cell damage without
    significantly damaging microbes
    C. The ability to harm the host cell and leave viruses
    alone
    D. The ability to titrate dosage that can be selectively
    and safely administered to a host

Answer 41

ANS: A
Selective toxicity is especially important in the design
of an antimicrobial, ensuring that the antimicrobial is
selectively toxic for the pathogen that is causing an
infection and disease while leaving the host unharmed
(A). Harming the host cell (B, C) is an unacceptable
choice. Titration (D) is not related to the selective
toxicity of an antimicrobial.

Question 42

46. The mechanism of action for naturally occurring
    penicillin and its synthetic derivatives such as methicillin
    and ampicillin is the inhibition of cell wall synthesis. The
    spectrum of action for beta-lactam antibiotics equally
    includes gram-negative and gram-positive bacteria.

A. Both statements are true.
B. Both statements are false.
C. The first statement is true, and the second statement
is false.
D. The first statement is false, and the second
statement is true

Answer 42

ANS: C
The first statement is true, and the second statement is
false (C). Penicillin and its synthetic derivatives such
as methicillin and ampicillin are beta-lactam drugs that
target the assembly of peptidoglycan in bacterial cell
walls. The second statement is false. Gram-positive
bacteria are targeted more efficiently by this group of
antibiotics because their cell walls contain a higher
amount of peptidoglycan and do not contain an outer
lipid membrane external to the peptidoglycan layer
such as the one found in gram-negative bacterial cells.
Choices A, B, and D do not accurately reflect the
statements.

Question 43

47. Erythromycin and tetracycline both act by
    A. disrupting cell membranes.
    B. disrupting cell wall synthesis.
    C. disrupting nucleic acid synthesis.
    D. inhibiting viral attachment.
    E. inhibiting protein synthesis

Answer 43

ANS: E
The mechanism of action for erythromycin and
tetracycline is to inhibit protein synthesis (E).
Erythromycin is a macrolide that binds to the 50S large
ribosomal subunit in prokaryotic cells. Upon binding,
it prevents messenger ribonucleic acid movement
through the ribosome, thereby halting protein synthesis. ANS: E
The mechanism of action for erythromycin and
tetracycline is to inhibit protein synthesis (E).
Erythromycin is a macrolide that binds to the 50S large
ribosomal subunit in prokaryotic cells. Upon binding,
it prevents messenger ribonucleic acid movement
through the ribosome, thereby halting protein synthesis.

Question 44

48. The total number of existing cases of a particular
    disease in a particular population within a given period
    is referred to as the
    A. rate.
    B. prevalence.
    C. incidence.
    D. proportion

Answer 44

ANS: B
The definition of prevalence (B) is total number of
already existing cases of a particular disease in a
particular population within a given period. Rate (A)
is the number of cases in a population expressed as a
percentage. Incidence (C) only concerns the number
of new cases in a given area or population during
a period. It does not include the number of already
existing cases that contribute to the total number of
cases of a particular disease. Proportion (D) compares
one population with the larger one to which it belongs.

Question 45

49. All are thought to be beneficial aspects of fever
    EXCEPT one. Which one is the EXCEPTION?
    A. Stimulating interferon responses
    B. Inhibiting microbial growth
    C. Stimulating the action of phagocytes
    D. Stimulating tissue repair

Answer 45

ANS: D
Fever usually occurs in the acute inflammatory phase,
which is not the period when tissue repair occurs (D).
Fever is a nonspecific immune response that stimulates
the actions of interferons (A) and phagocytes (C).
The higher body temperature inhibits the growth of
microorganisms (B) that may need the body to be at
normal temperature for maximal replication efficiency.

Question 46

50. Which reaction is characterized by degranulation of
    mast cells as a result of antigen–antibody complexes
    affixed to cell surfaces?
    A. Immune complex
    B. Cytotoxic
    C. Anaphylactic
    D. Delayed hypersensitivity

Answer 46

ANS: C
An anaphylactic reaction (C) is the most severe
example of a type I, immediate hypersensitivity
reaction. Within minutes after exposure to a previously
encountered allergen, preformed immunoglobulin E
(IgE) antibodies cause mast cells to be produced in
the tissue and basophils in the circulating bloodstream
to release histamine and other vasoreactive granules.
Massive vasodilation results in a drop in blood
pressure, and bronchoconstriction and edema of
the airways may cause a life-threatening reaction.
Immune complex (A), or type III, hypersensitivity
reactions occur when antigen–antibody complexes
leave the circulation and are deposited in body
tissues or in a localized area, resulting in an acute
inflammatory response. Lysosomal enzymes released
from neutrophils cause the type of tissue destruction seen in autoimmune diseases such as systemic
lupus erythematosus. Cytotoxic (B), or type II,
hypersensitivity occurs when the antibody attaches to
the surface of a tissue cell, usually a red blood cell.
Antibodies activate other complement antibodies
such as immunoglobulin G and immunoglobulin
M in blood, destroying the targeted red blood cells.
Reactions to blood transfusions of incompatible blood
types and fetal Rh incompatibility are examples of
this type of hypersensitivity reaction. The delayed
hypersensitivity (D), or type IV, cell-mediated
immune response involves production of lymphokines
from sensitized T-lymphocytes, causing conditions
such as contact dermatitis and the skin reaction seen in
the tuberculin skin test

Question 47

51. What is the etiologic agent of syphilis?
    A. Borrelia vincentii
    B. Actinomyces israelii
    C. Treponema pallidum
    D. Treponema denticola
    E. Histoplasma capsulatum

Answer 47

ANS: C
Syphilis is caused by the bacterial spirochete
Treponema pallidum (C). Borrelia vincentii (A) and
fusiform bacilli are the microorganisms associated with
necrotizing ulcerative gingivitis (NUG). Actinomyces
israelii (B) is the infectious agent in actinomycosis,
a disease with abscesses draining from the bacteria
into tissue. Treponema denticola (D) is one of the red
complex of microorganisms that are associated with
periodontitis. Histoplasma capsulatum (E) is one of the
causative pathogens associated with histoplasmosis, a
fungal infection of the lung.

Question 48

52. All are cardinal signs of inflammation EXCEPT one.
    Which one is the EXCEPTION?
    A. Pain
    B. Redness
    C. Swelling
    D. Localized heat
    E. Pale color
    F. Loss of function

Answer 48

ANS: E
Pale color (E), or pallor, is not a cardinal sign of
inflammation. The typical signs and symptoms of
inflammation are pain (A), or dolor; redness (B), or
rubor; swelling (C), or tumor; localized heat (D), or
calor; and loss of function (F), or laso functio. These
changes are primarily caused by increased vasodilation
and increased capillary permeability, which bring
additional blood flow to the area

Question 49

53. All of these cellular components increase disease
    virulence EXCEPT one. Which one is the
    EXCEPTION?
    A. Flagellae
    B. Glycocalyx
    C. Fimbriae
    D. Pili
    E. Lipopolysaccharides

Answer 49

ANS: A
Flagellae (A) are long, threadlike appendages with
a whiplike motion that allows the bacteria to move
through fluids and are not linked to virulence.
Glycocalyx (B), which is a capsule found on
some bacteria, aids in adherence and resistance to
phagocytosis, greatly enhancing bacterial virulence.
Fimbriae (C) are cellular projections that promote bacterial adherence and virulence. Pili (D) are tubelike
structures that allow transfer of genetic material
between bacteria, increasing drug resistance and
virulence. Lipopolysaccharides (E) are a component of
the cell wall of gram-negative bacteria.

Question 50

54. A memory or secondary immune response will
    generate a more rapid antibody response. It is more
    powerful than a primary immune response.
    A. Both statements are true.
    B. Both statements are false.
    C. The first statement is true, and the second statement
    is false.
    D. The first statement is false, and the second
    statement is true

Answer 50

ANS: A
Both statements are true (A). Memory or secondary
immune responses are much quicker and more
intense or powerful compared with primary immune
responses. The memory cells produced during the
primary immune response allow for a much quicker
response to a pathogen that has been previously
encountered by the host immune system. Primary
immune responses are slower and less powerful
because they must be activated on their first exposure
to the pathogen and are producing memory cells for
the first time. Choices B, C, and D do not accurately
reflect the statements.

Question 51

55. Which condition describes the body’s immune system
    reacting to its own tissues as if they were foreign?
    A. Hyperimmune reaction
    B. Autoimmune reaction
    C. Allergic reaction
    D. Immunodeficiency reaction

Answer 51

ANS: B
An autoimmune reaction (B) is the condition in which
the body’s immune system treats its own tissues as
if they were foreign. A hyperimmune reaction (A)
refers to an overproduction of antibodies but not
necessarily against the body’s own tissues. An allergic
reaction (C) is also an overreaction of the body’s
immune system but not to the body’s own tissues.
An immunodeficiency (D) is caused when the body’s
immune system is deficient.

Question 52

56. The relationship between herpes simplex 1 and herpes
    simplex 2 MOST closely matches the relationship
    between
    A. measles and mumps.
    B. chickenpox and shingles.
    C. smallpox and chickenpox

Answer 52

ANS: B
The varicella-zoster virus causes both chickenpox
and shingles (B), which are different clinical
manifestations of the same virus. This is similar
to the relationship between herpes simplex 1 (oral
herpes) and herpes simplex 2 (genital herpes).
Measles is caused by a virus that is entirely different
from the mumps virus. Measles may include a rash
that appears as flat, discolored areas (macules) and
solid, red, raised areas (papules), whereas mumps
causes enlargement of the parotid glands (A).
Smallpox has been eradicated, and its pustules are
firm and more embedded in skin compared with
those of chickenpox (C).

Question 53

57. Which virus enters the respiratory system and
    spreads via blood to the parotid glands to present as a
    characteristic disease sign?
    A. Severe acute respiratory syndrome (SARS) virus
    B. H1N1 influenza virus
    C. Mumps virus
    D. Rhinovirus

Answer 53

ANS: C
The mumps virus (C) originates in the respiratory
system and travels in the bloodstream to the salivary
glands to cause the characteristic sign of enlarged
parotid glands. The SARS virus (A), H1N1 influenza
virus (B), and rhinovirus (which causes common cold)
(D) infections are diseases of the respiratory system
but manifest primarily with respiratory symptoms.

Question 54

58. Which disease is characterized by the production
    of toxins that cause respiratory tract inflammation,
    paralysis of cilia, and a characteristic cough?
    A. Pertussis
    B. H1N1 influenza
    C. Tuberculosis
    D. Respiratory syncytial virus infection
    E. Chickenpox

Answer 54

ANS: A
Bordetella pertussis, the causative agent of pertussis
(A), or “whooping cough,” produces a tracheal
cytotoxin and results in a characteristic “whoop”
cough. H1N1 influenza (B), known as the “swine flu,”
may produce severe respiratory symptoms but does not
produce toxins. Tuberculosis (C) causes respiratory
tract inflammation and causes a cough but does not
produce toxins. Respiratory syncytial virus infection
(D) causes a mild respiratory disease in adults but may
cause severe respiratory problems in infants and young
children. Respiratory syncytial virus does not produce
toxins. Chickenpox (E) is transmitted by respiratory
droplets but does not fit the description above.

Question 55

59. Which oral pathogen can cause an infection that may
    lead to cardiovascular disease?
    A. Mycobacterium tuberculosis
    B. Fusobacterium nucleatum
    C. Borrelia burgdorferi
    D. Streptococcus mutans

Answer 55

ANS: B
The only pathogen on the list that can cause an
infection leading to a cardiovascular disease and
is only found in the oral cavity is Fusobacterium
nucleatum (B). Mycobacterium tuberculosis (A) causes
tuberculosis. Borrelia burgdorferi (C) is the bacterium
that causes Lyme disease. Streptococcus mutans (D) is
the bacterium that causes dental caries.

Question 56

60. Koplik spots are a distinctive oral manifestation of
    which diseases?
    A. Measles
    B. Mumps
    C. Rubella
    D. Meningitis
    E. Pneumonia

Answer 56

ANS: A
Koplik spots, which are small erythematous macules with
white necrotic centers, are a distinctive oral manifestation
of measles (A). Mumps (B) presents as swelling of the
parotid glands. Rubella (C) is similar to measles but does
not present with Koplik spots. Meningitis (D) presents
with neurologic signs and symptoms such as numbness
and stiff neck. Pneumonia (E) is the general term for
respiratory infections of the lung