Exam#3-2012

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Feb 20, 2013 (4 years and 4 months ago)

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Microbiology Exam #3
-
Fall 2012

Name____
Key
______________

Multiple choice. Choose
the best answer (2 points each)

1.___
D
__Pharmacogenomics refers to: a) identifying pathogens using molecular DNA techniques;
b)designing

chemotherapeutic drugs using biotechnology; c) comparing the susceptibility of pathogens
to

antimicrobial
drugs using molecular DNA techniques; d) tailoring the prescription of
chemotherapeutic drugs t
o a patient’s DNA sequences

2. ___
C
__Penicillins and c
ephalosporins: a) inhibit bacteria by different mechanisms; b) are cell wall
inhibitors and antimetabolites respectively; c) are bet
-
lactam antibiotics; d) are

protein synthesis
inhibiting antibiotics; e) kill virus but not bacteria

3.___
D
__ Which
of the
following strategies would be the
least
desirable and effective to use in
design
ing a chemotherapeutic drug to
selectively

inhibit or kill prokaryotic human pathogens? a)
protein synthesis inhibition; b) inhibition of DNA helicase and topoisomerase; c)

cell wall inhibition;

d) disruption of cell
(plasma)
membranes; e) inhibition of the biochemical pathway leading to the
synthesis of folic acid.


4.__
E
___
If you have a penicillin allergy, the safest antibiotic for your physician to pre
scribe would be:
a) ampicillin; b) augmentin; c) cephalosporin;
d)
methicillin; e) erythromycin

5.___
A
__
The first “magic bullet” chemotherapeutic drug that was developed that specifically targeted
most bacterial pathogens

without adversely harming host tissues: a) sulfonamide; b) salvarsan;

c) penicill
in G; d) fluoroquinolines; e) PABA

6.___
B
__
The bectam lactam nucleus of this antibiotic has two “R” groups allowing for more
opportunities to produce next gene
ration molecules with broader spectrum, and fewer side effects: a)
clavulanic acid; b)
cephalosporin; c)

tetracycline; d) vancomycin; e) chloramphenicol

7.___
E
__
This antibiotic is a relatively small molecule, ca
n cross the blood
-
brain barrier,
but is so t
oxic it
should only be used in life
-
threatening situations (such as meningitis): a) sulfonamide; b) tetracycline
c) bacitracin; d) streptomycin; e) chloramphenicol

8.__
C
___
Which of the following statements about therapeutic index (TI) is
not

true? a) a

drug with a
higher TI is preferred over a drug with a lower TI ; b) you must know MIC before you can calculate TI;
c) A Kirby
-
Bauer test must be completed before you can calculate TI; d) the toxic dose of a drug must be
known before you can calculate

TI; e) b and d

9.__
A
___
A physician prescribing this drug would be least worried about the serious side effect of
aplastic anemia? a)
Cipro (a fluoroquinoline); b) erythromycin
;

c) tetracycline; d) chloramphenicol;

e) streptomycin


10.__
B
___
Trimethoprim (Septra) and sulfonamide are often prescribed together because they have a
synergistic effect. Both
of these
drug
s

belong to this class of chemotherapeutic drugs: a) cell wall
inhibiting antibiotics; b) antimetabolites; c) protein

synthesis inhibiting antibiotics; d) antiviral drugs;

e) DNA replication inhibitors.

11.__
B
___
All human

microbial symbiotic relatio
nships begin with this phenomenon:

a) colonization;
b) contact; c) infection; d) morbidity; e) virulence

12.___
C
__
T
he benefit to a pathogen

possessing this virulence factor is not completely understood
but
current theories suggest that it involves increasing iron availability to promote growth of the pathogen:
a)streptokinase; b) coagulase; c) hemolysins; d) leukoc
idin; e) cholera toxin

13.__
B
___
Tetanus toxin: a) is the most potent known biological toxin; b)

is a neurotoxin that inhibits
spinal inhibitory neuro
ns; c) prevents the release of
acetylcholine into the synapse of the myoneural
junction;

d) is an endotoxi
n; e)
activates adenylate cyclase resulting in the formation of CAMP.


14.__
A
___
Prio
r to the onset of the
easily recognizable
symptoms of a viral cold infection

(fever, cough,
sneezing), Interlukins produced by your immune system often cause generalized ma
laise and a

yucky

feeling” that are the first

indication
that you are becoming ill. This would be associated with which stage
of infection? a)prodromium; b) incubation; c) period of invasion; d) convalesc
ent;
e) sequale

15.__
D
___
Assume that you cont
ract an infectious disease via a
door
-
handle of a public restroom
. The
term that would best describe the route of transmission by which acquired your disease would be:

a)
direct
vertical
; b) direct horizontal; c) direct oral fecal; d) indirect fomi
te; e) direct droplet.

16.__
C
___
Suppose after eating at SAGA, you experience fever and nausea and the source of your
discomfort

is determined to be the lipid A

component of lipopolysaccharide. In scientific terms you are
most likely suffering from: a)

the effects of a neurotoxin; b)

the effects of
a hemotoxin; c) the effect of
an endotoxin; d) a toxoid; e) an A
-
B toxin.

17.__
A
___
If a bacterium is highly virulent; a) it would be expected to have a low infectious dose;

b) it would be expected

to have a high therapeutic index; c) it would be categorized as a zoonosis;

d) it would be unlikely to cause nosocomial infections.

18.__
D
___

Incidenc
e and prevalence of diseases is

most likely the province of: a)
metagenomics;

b) syn
dromes; c) noncommunicable diseases; d) epidemiology; e) vertical disease transmission.

19.__
B
___
This toxinoses is subdivided into the categories food, infant, or wound: a) diphtheria;

b) botulism;
c)
cholera; d) toxic shock syndrome; e) imp
etaigo

20._
C
____
Suppose that in 2012 the number of cases of Lyme disease
reported
in the up
per New
England states increased

from the historical incidence

of 50 cases /10,000

people to
100 cases/10,000
people. An epidemiologist would define this disease as

a(n): a) endemic; b) sporadic;
c)
epidemic; d)
pandemic; e) syndrome


21.___
D
__These cells are not involved directly in the humoral immune response: a) plasma cells
;


b) B
-
lymphocytes; c) T
-
helper cells; d) eosinophils; e) macrophages

22.___
B
__

These agranulocytes have a similar function as T
-
killer cells but they are not activated by
antigen: a) dendritic cells; b) NK
-
cells; c) macrophages; d) Kupffer cells; e) P

MN leukocytes

23.__
B
___
The first line of defense is characterized by thes
e terms: a) innate and specific; b) innate and
nonspecific; c) acquired and nonspecific; d) acquired and specific; e) innate and acquired

24.__
E
___
Histiocytes are most associated with this aspect of the human immune system: a) humoral
immunity; b) cell me
diated immunity; c) second
ary lymphoid tissue; d) ciliary
escalator; e) macrophages
and the RES (reticuloendothelial system)

25.__
D
___
A part of your body’s first line of defense, this substance is secreted by the gall bladder and
selectively inhibits gram (+) bacteria: a) lysozyme; b) gamma globulin; c) eosin; d) bile salts;
e) defensins

26.__
D
___
Which of the following statements about lymph nodes is
false
? a
) they are a type of
secondary lymphoid tissue; b)
they serve much the same function for the lymphatic system that the
spleen serves for the circulatory system; c) B and T lymphocyte population
s in the nodes tend to occupy
different l
ocations within the nodes;
d) very few immune reactions occur in the nodes, most occur in the
blood;

e) nodes tend to be clustered in certain regions of the body including the neck, armpits, and
groin.

27.__
B
___

Wh
en these cells leave the blood and migrate into the tissues, they swell 5
-
10 X and
differentiate into macrophages: a) dendritic cells; b) monocytes;

c)
Langerhans cells; d) NK cells;
e) basophils

28.__
E
___
The third line of the immune syste
m i
s characterized by: a) memory;
b) specificity;


c) redundancy; d) a and c; e) all of the above

29.__
E
___
The

education


o
f B
-
lymphocytes (
formation of
a specific receptor)

and the elimination of
B
-
lymphocytes that will react t
o self
-
antigens take place
in an adult

in this location
: a) liver; b) lymph
nodes; c) MALT; d) thymus; e) bone marrow.

30.__
D
___
Which

of the following is
not

part of blood serum? a) (Gamma) globulin proteins;
b) complement proteins; c) wate
r; d) clotting proteins; e) none of the above (all are found in blood
serum)

31. (4 points each) Agree or disagree with the following statements. In either ca
se, fully defend your
position.

A
.
Staph aureu
s

is a pathogen of

concern because it not only has
multiple virulence factors but they also
represent
each of the 3 major categories

of known virulence factors
.

Agree
-
SA has virulence factors that are a) anitiphagocytic (given an example), b) exoenzymes (given
an example), and c
) toxins (given an example)


B. We know that the development of drug resistance pathogens is a significant medical problem.
Unfortunately, no reasonable solutions to this problem have been prop
o
sed.

Disagree
-
Several reasonable strategies have been propos
ed including:

A)

use narrow not broad spectrum antibiotics

B)

eliminate antibiotics from cattle feed

C)

identify pathogens (take cultures) so you know the pathogen is bacterial and not viral

D)

check suspected pathogen for drug resistance (MIC and E tests)


C. The onl
y known mechanism by which bacteria have been shown to develop resistance to an antibiotic
is the production of enzymes (such as penicillinase) that inactivate the drug.

Disagree
-

Several mechanisms have been identified including:

a.

receptor mutations that

prevent drug from binding to pathogen

b.

activation of drug pumps

c.

mutation result in change in internal drug receptors (ribosomes)gets around a blocked
pathway

d.

a metabolic shunt that


D. There is a relationship between two branches of the immune system that

were once thought to be
entirely separate (cell
-
mediated immunity and humoral immunity).

Agree
-
The humoral response (secretion of antibodies) is the result of activation of B
-
plasma cells.
However, cell
-
mediated immunity is generally required to activate

the B
-
plasma cell. This involves T
-
helper cells (which have themselves been activated by an antigen presented to them by a
macrophage) binding to a B
-
lymphocyte. This binding activates the B
-
lymphocyte to differentiate
into plasma cells which secrete a
ntibody.

32. (8 points) Compare and contrast the mode of action, applications, and limitations of the
chemotherapeutic drugs penicillin and sulfonamide.

Both drugs are reasonably selective for killing prokaryotic pathogens but not harming human cells.

Penicillin is a beta
-
lactam antibiotic that inhibits peptidase which are required to synthesize
peptidoglycan. As PG is selectively broken down to allow for bacterial cell growth, inhibition of its
resynthesis weakens the cell wall so the cell eventually

lyses and dies. Penicillin G is the antibiotic of
choice for killing non
-
resistant gram positive organisms. However, it is poorly absorbed (must be
injected) and is not effective against gram (
-
) bacteria. Additionally, allergies to penicillin are no
t
uncommon.

Sulfonamide is n antimetabolite drug. It competitively inhibits the synthesis of folic acid (by
mimicking the normal substrate PABA) which is necessary
for synthesis of nucleotides and amino
acids. Sulfonamide is effective against virtually a
ll bacteria except those that obtain their folic acid
from the environment rather than synthesizing it (Mycobacterium). This drug does have some side
effects including nausea and dizziness.


33. (8 points)

Contrast the bacterial diseases gas gangrene and

botulism in regard to the following:
causative organism, how the pathogen causes the disease (the mechanism), treatment options,
and
cause
of death (
if treatment is not effective).

Gas gangrene is caused by the anaerobe Clostridium perfringes. Tissue dam
age creates an anaerobic
pocket where Clostridium spores can germinate. The bacteria produce a number of exoenzymes
which kill adjacent cells and cause tissues to fall apart. This allows the infection to spread into healthy
tissue. Fermentation of muscle

proteins creates gas which leads to swelling and further blocks blood
flow (causing more tissue death). Treatment options include amputation, antibiotics, and hyperbaric
oxygen. If these are not successful, mortality rate is as high as 40% usually due

to cardiovascular
chock and kidney failure.

Botulism is a neuroexotoxin produced by the anaerobe Clostridium botulinum (
often times as a result
of the anaerobe growing in food that has been improperly canned). The toxin inhibits release of
acetylcholine onto the myoneural junction resulting in flaccid paralysis of muscles. Death is usually
due ot respiratory or cardiac fa
ilure. Antibiotics can be used to kill the bacteria and

ant
itoxins can
inactivate the toxin. This may need to be augmen
ted by mechanical ventilators to allow the patient
to survive while the antitoxins and antibiotics are working.



34. (8 points)

Des
cribe the difference between B and T lymphocytes in terms of location of
differentiation and their general role in the immune response (the type of immunity are responsible for).
Describe the effector cells that B and T lymphocytes
each
produce and briefl
y describe the role that
each effector cell plays in the immune response. What must happen in order for both B and T
lymphocytes to be activated so they can begin differentiating into effector and memory cell
populations?

B lymphocytes differentiate in t
he bone marrow and are involved in humoral immunity and T
-
lymphocytes differentiate in the thymus and are involved in cell
-
mediated immunity.

To be activated to differentiate, both cells types must be exposed to their specific antigen (often
through the in
volvement of an antigen presenting cell).

Differentiation of B
-
lymphocytes results in memory cells and effector cells. The effectors are plasma
cells which secrete antibody.

T
-
lymphocytes differentiate into memory cells and three populations of effecto
r cells:

a.

T
-
helper secrete lymphokines that help activate B
-
lymphocyte development

b.

T
-
killers destroy host cells that are cancerous or infected by virus

c.

T
-
supressors turn off the immune response when the the threat has been eliminated.