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MICROBIOLOGY EXAM I
CODE 1
SIMPLE COMPLETION:
Each of the questions or incomplete statements in this group is followed by four or five
suggested answers or completions. Select the one which is best in each case and mark the
corresponding letter on the answer sheet:
1. Which one of the following is most likely to be associated with clinically important
infection when recovered from a blood culture in a patient with fever?
A. Escherichia coli
B. Bacillus spp.
C. Coagulase negative Staphylococcus
D. Propionibacterium acnes
E. Micrococcus
2. A first year student develops a "boil" in his nose. Which one of the following is NOT
a true statement (which one is FALSE)?
A. The student should receive antibiotics.
B. Blood cultures are nearly always positive in the condition.
C. The causative organism is probably Staphylococcus aureus.;
D. A nose culture is not needed to make the diagnosis.
E. The proximity of the infection to the brain is a concern
3. Which one of the following is NOT an infection caused by a normal body flora
organism?
A. Pneumonia caused by Legionnella pneumophila acquired during a hotel
convention.
B. E. coli urinary tract infection.
C. Pseudomonas blood stream infection in a patient with lymphoma (malignancy
of lymphatic system) and neutroppnia (abnormally low number of
polymorphonuclear leukocytes in the blood stream).
D. Streptococcus viridans endocarditis.
E. Post-viral bronchitis.
4. Which of the following is the LEAST likely to be associated with the spread of normal
floral organisms from one person to another, potentially resulting in an infection?
A. Stethoscopes
B. Environmental air
C. Hands
D. Clothing/bedding
E. Breathing, coughing, sneezing
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5. Which one of the following is the most pathogenic species?
A. Anaerobic streptococcus
B. Shigella sonnei
C. Bacillus spp.
D. Staphylococcus faecalis
E. Candida albicans
6. Which one of the following is NOT part of the sepsis syndrome (shock and body organ
failure in a patient with blood stream infection by a gram negative bacteria)?
A. Myocardial (heart muscle) function depression
B. Underperfusion of body tissues at the level of the microcirculation
C. Disseminated intravascular coagulation
D. Production of coagulase leading to boils
E. Cytokine and endotoxin release
7. Which one of the following is probably an "epidemic" rather than an "endemic"?
A. Three unrelated persons in Houston experience influenza B infection, during a
Winter season, found by city-wide screening
B. Two persons develop clinically apparent hepatitis A after eating raw oysters at
a local restaurant
C. One senior medical student acquires asymptomatic infection with M tuberculosis
(skin test conversion)
D. Two of five students traveling to Cozumel for a long holiday, for scuba diving,
develop diarrhea
E. Five children of 1,000 screened develop asymptomatic (subclinical) infection due
to Epstein-Barr virus over a two year period of time
8. A major step in the pathogenesis of listeriosisis:
A. The formation of antigen-antibody complexes with resultant complement
activation and tissue damage.
B. The release of hyaluronidase by Listeria monocytogenes, which contributes to
its dissemination from local sites.
C. The antiphagocytic activity of the L. monocytogenes capsule.
D. The ability of polymorphonuclear leukocytes to phagocytize and destroy L.
monocytogenes early in the course of disease.
E. The survival and multiplication of L. monocytogenes within mononuclear
phagocytes and host epithelial cells.
9. Among renal transplant and adult cancer patients, L. monocytogenes is the leading cause of:
A. tonsillitis
B. otitis media
C. conjunctivitis
D. sinusitis
E. bacterial meningitis
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10. Which of the following species synthesize(s) a bacterial protein with adenylate cyclase
activity, which plays a role in pathogenesis?
A. Bordetella pertussis
B. Bacillus anthracis
C. Vibrio cholerae
D. a and b
E. b and c
11. The definitive identification of C. diphtheriae isolated from a throat swab:
A. is based upon the demonstration of typical pleomorphic rods in methylene blue
stained smears
B. is based upon gray-black colony formation on;byteind tellurite agar plates
C. necessitates the demonstration of exotoxin by the organism
D. must be done before therapy can be initiated
E. is based upon the demonstration of typical pleomorphic rods in Gram-stained
smears
12. Which of the following is correct? Bacterial capsules:
A. are found on all bacteria
B. are composed of peptidoglycan
C. are localized between the outer membrane and cytoplasmic membranes of Gram
negative bacteria
D. inhibit phagocytosis
E. represent the outer surface of all Gram positive bacteria
13. Which of the following is FALSE regarding bacterial flagella?
A. They are helical in shape.
B. They produce motility by a rapid side-to-side motion.
C. The flagellar filament is usually a polymer of a single protein subunit.
D. The flagellar motor is considered to be the most efficient biological "machine".
E. Flagella are often important in terms of pathogenesis.
14. Which of the following is correct? Endotoxin:
A. is produced by Gram-positive bacteria
B. has profound biological effects due to the Lipid A moiety
C. has important enzymatic activities
D. is composed of protein
E. is usually found in secreted rather than cell-associated form
15. An important property of the cell envelope of acid-fast bacteria is:
A. the abundance of mycolic acid in the cell wall
B. the presence of porins in the outer membrane
C. the lack of oxidative phosphorylation enzymes ,
D. the absence of a peptidoglycan layer
E. the accumulation of dipicolinic acid in the periplasmic space
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16. Which of the following organisms is INCORRECTLY matched with the disease it most
commonly causes?
A. Staphylococcus saprophyticus - urinary tract infections
B. Streptococcus pyogenes - pharyngitis
C. Enterococcus faecalis - neonatal meningitis
D. Viridans streptococci - dental caries
17. Within 5 hours of returning home from lunch at your most favorite, fast food restaurant,
you feel very sick and are vomiting. The most likely causative organism is:
A. Staphylococcus aureus
B. Streptococcus pyogenes
C. Staphylococcus epidermidis
D. Escherichia coli
18. Which of the following organisms, when isolated in the blood, requires the synergistic
activity of penicillin plus an aminoglycoside for appropriate therapy?
A. Streptococcus pyogenes
B. Enterococcus `faecalis
C. Staphylococcus aureus
D. Streptococcus pneumoniae
19. Which of the following is an INCORRECT statement?
A. The presence of Streptococcus bovis in the blood is associated with increased
risk for colon cancer.
B. Streptococcus agalactiae is a transient colonizer of the female genital tract.
C. Streptococcus pyogenes can cause a variety of diseases including acute
rheumatic fever and a "toxic shock" - like syndrome
D. Staphylococcus aureus is a common cause of catheter related blood stream
infections.
20. Which of the following processes allow(s) the transfer of bacterial DNA between
different individual cells:
A. Transformation
B. Conjugation
C. Generalized transduction
D. All of the above
E. None of the above.
21. How is the transformation mechanism different between E. coli and Neisseria species.
A. They are the same and not different.
B. DNA enters E. coli cells only after chemical or electrical treatments, whereas
Neisseria species are naturally competent.
C. Neisseria transformation involves recombination, whereas E. coli does not.
D. E. coli DNA must be cut with restriction endonucleases before it enter
competent cells, whereas Neisseria DNA does not need to be restricted.
E. None of the above.
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22. Which properties are characteristic of bacterial DNA polymerases?
A. They catalyze addition of bases to growing DNA strands in a 3'to 5' direction.
B. They show an absolute requirement for a DNA or RNA primer.
C. They participate in replication, but not in DNA repair.
D. They are present in only one form.
E. None of the above.
23. What is the first conceptual step in designing a polymerase chain reaction protocol for
diagnostic purposes?
A. Determine a pair of primers that will give a unique, appropriate amplification
product.
B. Determine the appropriate concentration of DNA polymerase to use in the
reaction.
C. Determine the appropriate concentration of primers to use in the reactions.
D. Determine the time and temperature required to melt hybrids formed between
complementary DNA strands.
24. Which of the following characteristics are possessed by the antibiotic-resistance
conferring R plasmids?
A. They contain Ira genes that mediate self transmissibility.
B. They contain an origin of replication.
C. They are present in very low copy numbers.
D. Depending on the plasmid, they can confer resistance to more than one antibiotic.
E. All of the above.
25. Mutations in the human gene that is responsible for nonpolyposis colon cancer is
strongly, evolutionarily related to the bacterial mutS gene, which encodes a protein that
binds to DNA mismatches in the methyl-directed-mismatch repair system. This finding
means:
A. Human nonpolyposis cancer is likely caused by a defect in DNA mismatch repair.
B. The product of the human gene is likely an enzyme that recognizes and binds to
mismatches.
C. The mismatch repair system appears to be ancient and essential since it is conserved in
these very different species.
D. All of the above.
E. None of the above.
26. Which of the following genotypes would be lethal to a bacterial cell (where a + means
the function is present, and a - means lack of a function):
A. Restriction+ Modification+
B. Restriction- Modification+
C. Restriction+ ModificationD. Restriction- ModificationE. All of the above.
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27. Suppose you wanted to apply the luciferase transducing phage approach developed for
M tuberculosis, which was discussed in class, to a completely different, unrelated
bacterial species. What is the first step that you would take? (Note that phage are
usually host-species specific).
A. Clone the luciferase gene into a plasmid that can replicate in the new
bacterial species and test whether the substrate, luciferin, is taken up by this
new species in a way that bioluminescence can occur.
B. The general approach cannot be applied to other bacterial species, and there is
no first step to take.
C. Simply infect the new bacterial species with the luciferase phage already
constructed for M. tuberculosis and perform the bioluminescent assay in the
same way.
D. Mix together M. tuberculosis luciferase phage and a temperate phage specific for
the new bacterial species and infect the new bacterial species.
28. You would like to design a diagnostic test for the 3 base-pair deletion that causes
cystic fibrosis. What would be a reasonable method and efficient method?
A. Clone the entire CF gene from patients and determine the DNA sequence of the
cloned gene in each case.
B. Design a bacteriophage luciferase assay that will detect function of the CF
gene.
C. Choose two oligonucleotide primers that immediately flank the known CF
deletion, amplify the region by the polymerase chain reaction (PCR), and
confirm the presence of the deletion in the PCR product by electrophoretic
methods, including binding of the MutS protein.
D. Use hybridization methods to isolate the CF mRNA molecule and then
determine its sequence to confirm the missing bases.
E. Purify and sequence defective CF protein from each patient.
29. Which of the following is considered a beta-lactam?
A. vancomycin
B. imipenem
C. azithromycin
D. pyrimethamine
30. Resistance to which of the following has been 'shown to result from enzymatic
inactivation of the antibiotic by the bacteria?
A. chloramphenicol
B. sulfonamides
C. ciprofloxacin
D. trimethoprim
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31. There is an old saying that goes ". . . all roads lead to Rome. .". In the case of
bacterial metabolism, that statement might be rephrased to read "all roads lead to:
A. glucose"
B. glutamic acid".
C. pyruvate".
D. ATP"
E. DNA".
32. The most primitive form of a biologically useful, energy generating reaction is referred
to as:
A. photophosphorylation
B. aerobic phosphorylation
C. anaerobic phosphorylation
D substrate level phosphorylation
E. high energy phosphorylation
33. The time it takes one bacterium to become two bacteria is referred to as:
A. the culture doubling time
B. the generation time
C. the mass doubling time
D. the happy time
E. none of the above
34. A non-viable bacterium is one in which:
A. the cell is missing an essential growth factor
B. the oxygen in the surrounding environment has been depleted
C. the cells are in the stationary phase
D. the cell has been ingested by a polymorphonuclear leucocyte
E none of the above
35. A heterotroph, as applied to bacteria, is one in which:
A. organic nitrogen is the sole source of nitrogen
B. vitamins must be provided externally in the growth medium
C. organic carbon is the sole source of carbon
D. complex carbohydrates are essential to cell survival
E. all of the above
36. Siderophores are a class of compounds that enable bacteria to compete effectively for:
A. CO2
B. O2
C. Ca2+
D. Fe2E. all of the above
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37. The proton motive force, pmf, has as a component the:
A. Na- concentration inside the cell versus that outside the cell
B. difference in pH outside the cell versus that -inside the cell
C. K+ concentration outside the cell versus that inside the cell
D. Ca2+ concentration inside the cell versus that outside the cell
E. none of the above
38. Bacterial chemotaxis refers to the movement of bacteria:
A. through the use of flagella
B through the expenditure of energy
C. through the availability of suitable carbon compounds
D. through the availability of a suitable carbon source
E. all of the above
39. The rate of bacterial growth is greatest
A. at increasing temperature
B. at optimum temperature
C. at decreasing temperature
D. at changing temperature
E. none of the above
MATCHING:
Match the following organisms with common tests used in their identification. Answers may be
used once, more than once, or not at all.
Questions 40-43
40. _____Enterococcus faecalis
41. _____Staphylococcus aureus
42._____ Streptococcus agalactiae
43. _____Streptococcus pneumoniae
A. CAMP test positive
B. Coagulase positive
C. Bile esculin; growth in 6.5% NaC1
D. Optochin susceptibility
E. Bacitracin susceptibility
Questions 44-46
A. erythromycin (tetracyclines, aminoglycosides)
B. sulfonamides
C. penicillin
D. pyrimethamine
E. fluoroquinolones
44._____ Interferes with cell wall synthesis
45. _____Interferes with DNA replication
46. _____Interferes with protein synthesis
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Questions 47-49
A. Ribosomal resistance
B. Enzymatic modification by adding hydroxyl or amino groups
C. Increased efflux due to an active pump
47. _____Resistance to tobramycin
48. _____ Mutation to high level streptomycin resistance
49. _____ Resistance to tetracycline
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ANSWERS:
25. D
26. C
27. A
28. C
29. B
30. A
31. C
32. D
33. B
34. E
35. C
36. D
37. B
38. B
39. B
40. C
41. B
42. A
43. D
44. C
45. E
46. A
47. B
48. A
49. C
1. A
2. B
3. A
4. B
5. B
6. D
7. B
8. E
9. E
10. C
11. C
12. D
13. B
14. B
15. A
16. C
17. A
18. B
19. D
20. D
21. B
22. B
23. A
24. E
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