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 to a patient’s DNA sequences
2. ___C__Penicillins and cephalosporins: 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
designing 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 prescribe 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) penicillin 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 generation 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, can cross the blood-brain barrier, but is so toxic 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 drugs 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 relationships begin with this phenomenon: a) colonization;
b) contact; c) infection; d) morbidity; e) virulence
12.___C__The 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) leukocidin; e) cholera toxin
13.__B___Tetanus toxin: a) is the most potent known biological toxin; b) is a neurotoxin that inhibits
spinal inhibitory neurons; c) prevents the release of acetylcholine into the synapse of the myoneural
junction; d) is an endotoxin; e) activates adenylate cyclase resulting in the formation of CAMP.
14.__A___Prior 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 malaise 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) convalescent; e) sequale
15.__D___Assume that you contract 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 fomite; 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___ Incidence and prevalence of diseases is most likely the province of: a) metagenomics;
b) syndromes; 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) impetaigo
20._C____Suppose that in 2012 the number of cases of Lyme disease reported in the upper 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 these 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 mediated immunity; c) secondary 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 populations in the nodes tend to occupy
different locations 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___ When 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 system is characterized by: a) memory; b) specificity;
c) redundancy; d) a and c; e) all of the above
29.__E___The “education” of B-lymphocytes (formation of a specific receptor) and the elimination of Blymphocytes that will react to 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) water; 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 case, fully defend your
position.
A. Staph aureus 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 proposed.
Disagree-Several reasonable strategies have been proposed including:
A)
B)
C)
D)
use narrow not broad spectrum antibiotics
eliminate antibiotics from cattle feed
identify pathogens (take cultures) so you know the pathogen is bacterial and not viral
check suspected pathogen for drug resistance (MIC and E tests)
C. The only 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 Thelper 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 antibody.
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 not
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 all 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 damage 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 failure. Antibiotics can be used to kill the bacteria and antitoxins can
inactivate the toxin. This may need to be augmented by mechanical ventilators to allow the patient
to survive while the antitoxins and antibiotics are working.
34. (8 points) Describe 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 briefly 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 the bone marrow and are involved in humoral immunity and Tlymphocytes 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 involvement 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 effector 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.