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MICROBIOLOGY EXAM I
Code 4
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 of the following is an example of a genotypic property?
A. Growth rate in liquid medium.
B. MIC antibiotic resistance in broth tubes.
C. The sequence of missense mutations in genes that impart antibiotic resistance.
D. The permeability property, of bacterial cell walls, to antibiotics.
E. The size and shape of bacterial cells in media containing a sublethal dose of
antibiotics.
2. Which of the following methods of transport involves specificity without the utilization
of energy?
A. Diffusion
B. Group translocation
C. Permease
D. Facilitated diffusion
E. None of the above
3. The molecules involved in actual proton translocation (proton pumping) within the
membrane belong to a class of compounds called:
A. Siderophores
B. Flavins
C. Cytochromes
D. Quinones
4. Which of the following cannot serve as the ultimate oxidant during anaerobic
respiration?
A. S
B. SO4
C. N03D. N02E. None of the above.
5. Which of the following is true of both Bacillus anthracis and Corynebacterium
diphtheriae infection?
A. A blood culture is the most important specimen to obtain in suspected cases.
B. Route of entry can be cutaneous or oral.
C. Antitoxin therapy should be given early upon clinical suspicion.
D. Non-toxigenic strains can remain pathogenic.
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6. Which of the following is true of both Listeria monocytogenes and Bacillus cereus?
A. The organism can penetrate the host cells of the epithelial lining.
B. Infection is primarily found in immunocompromised patients.
C. Infection can often be traced to contaminated food.
D. The organism produces an enterotoxin.
7. Which of the following organisms is incorrectly matched with a disease it most
commonly causes?
A. Group B streptococci, neonatal meningitis'
B. Viridans streptococci, bacterial endocarditis
C. Staphylococcus aureus, toxic shock syndrome
D. Streptococcus pyogenes, urinary tract infections
8. A patient comes to the emergency room with complaints of stomach upset. You note
mat he has a rash covering his body and that he is becoming increasingly hypotensive.
The blood cultures you drew were positive within 24 hours for gram positive cocci in
clusters. The most likely causative organism is:
A. Group B streptococci
D. Staphylococcus aureus
C. Enterococcus sp.
D. Staphylococcus sp. not S. aureus
9. The most likely therapy for the patient in the above question is:
A. Amphotericin B
B. Aminoglycosides
C. Nafcillin
D. Ampicillin
10. Which of the following organisms must be treated with combination therapy (most
commonly penicillin and gentamicin) when isolated in multiple blood cultures?
A. Streptococcus agalactiae
B. Staphylococcus sp. not S. aureus
C. Enterococcus sp.
D. Streptococcus bovis
11. A patient presents to the emergency room after several days of "flu-like" symptoms.
You collect a sputum sample on which the laboratory reports a Gram stain of dam
positive, lancet shaped diplococci. What is your diagnosis?
A. S. pneumoniae pneumonia
B. Group B streptococcal sepsis
C. Staphylococcal pneumonia
D. Toxic shock syndrome
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12. The laboratory calls to alert you that a patient, who has been in the intensive care unit
of the hospital for a long period of time, has several blood cultures with Gram positive
cocci in clusters. You suspect the diagnosis to be line related sepsis due to which
organism? ("Line related sepsis" is sepsis related to the presence of, for example, an IV
tube or line.)
A. Group A streptococcus
B. Clostridium difficile
C. Staphylococcus sp. not S. aureus
D. Viridans streptococci
13. Which statement is incorrect about Streptococcus pyogenes?
A. It is a common cause of bacterial pharyngitis.
B. Complications due to this organism include acute glomerulonephritis due to the
presence of immune complexes.
C. It usually causes self-limited disease and therefore disease due to it is not
routinely treated.
D. It can cause acute rheumatic fever due to cross reaction of its cell wall antigens
with heart tissue antigens.
14. Which microbial virulence property relates to the occurrence of a "boil" in Staphylococcus
aureus infection?
A. Cord factor
B. M protein
C. Streptokinase
D. Coagulase
15. Which are examples of "epidemics"?
A. 35 cases of hepatitis over a 1 year's period of time over which time 5 cases were
expected.
B. 5 cases of Salmonella gastroenteritis following exposure to a common restaurant
meal.
C. 2 cases of diarrhea occurring over 2 days in a family of 5.
D. A single case of botulism in Houston.
E. All of the above.
16. Which of the following are microbial factors important in the pathogenesis of septic shock?
A. E. coli enterotoxin
B. Complexes of polysaccharide, protein and lipid
C. Erythrogenic toxin
D. Streptokinase and hyaluronidase
TRUE OR FALSE:
Choose the best possible answer. A = True; B = False
17. _____Diphtheria (caused by C. diphtheriae) can be prevented by immunization
with DT toxoid; it can be treated with DT antitoxin.
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18._____ Staphylococcus aureus grown from a blood culture is an infection, but Staphylococcus
aureus grown from nasopharyngeal swab is colonization by normal flora.
19. _____The oxidation of an organic molecule through glycolysis and the gradual release of
energy increases the efficiency of cellular metabolism.
20.______ Substrate levels phosphorylation requires that the cell membranes be in an energized
state.
21. ______ Fermentations are important energy yielding biochemical sequences because they
enable a potential pathogen to live in the absence of oxygen.
22. ______ When intestinal flora leaks into the abdominal cavity, an abdominal abscess can
form. This abscess is often caused by the anaerobes in the intestinal flora, because the intestinal
aerobes and facultative anaerobes rapidly utilize all the available oxygen in the abdominal cavity,
creating an anaerobic environment.
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:
23. Which of the following properties are shared by prokaryotes and eukaryotes?
A. Ribosome size
B. Peptidoglycan layer
C. Chemical nature of genetic material
D. Mitochondria structure and function
E. Nuclear envelope
24. Which structure is found in all bacteria?
A. Capsular polysaccharide
B. Flagella
C. Pili
D. Outer membrane
E. Cytoplasmic membrane
25. Lysozyme produced by humans and other mammalian hosts:
A. Cleaves peptidoglycan between N-acetyl-glucosamine (NAG) and N-acetylmuramic acid (NAM) residues.
B. Inhibits the addition of amino acids to NAG.
C. Disrupts the outer membrane of gram negative bacteria.
D. Destroys lipopolysaccharide.
E. Results in a sterile environment in the mouth.
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26. The portion of the lipopolysaccharide molecule that varies among different bacteria and
thus exhibits antigenic differences is the:
A. Lipid A.
B. Core polysaccharide.
C. Dipicolinic acid.
D. Side chain polysaccharide.
E. Exotoxin component.
27. Bacterial pili are involved in:
A. Adherence to host cells.
B. Motility.
C. Resistance to heat.
D. Resistance to phagocytosis.
E. Endotoxic activity.
28. Penicillin inhibits bacteria because it:
A. Binds to acyl-D-alanyl D-alanine in ribosomes.
B. Binds to acyl-D-alanyl D-alanine in cell wall peptidoglycan precursors.
C. Resembles D-alanyl D-alanine and binds to cell wall synthesis enzymes.
D. Disrupts the inner membrane.
29. Penicillin G remains highly active against which of the following?
A. Enterococcus
B. Staphylococcus aureus
C. Neisseria meningitidis (meningococci)
D. Escherichia coli
30. Beta-lactamase production is a common mechanism of resistance to penicillin in which
of the following organisms?
A. Group A streptococci
B. Neisseria gonorrhoeae
C. Both
D. Neither
31. Antibiotic resistance to which of the following is caused by a by-pass mechanism (an
alternative dihydrofolate reductase)?
A. Erythromycin
B. Trimethoprim
C. Tetracycline
D. Ciprofloxacin
32. Antibiotic altering enzymes commonly cause resistance to which of the following?
A. Vancomycin
B. Trimethoprim
C. Aminoglycosides
D. Fluoroquinolones (e.g., ciprofloxacin)
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33. The proportion of antibiotic resistant bacteria has increased along with the widespread
use of antibiotics. This is due to the fact that antibiotics:
A. are unstable in vivo.
B. act as agents of selection for resistant organisms..
C. are mainly bacteriostatic in vivo.
D. are powerful mutagens.
34. Ribosomal resistance is a cause of resistance to:
A. Streptomycin
B. Vancomycin
C. Sulfonamides
D. Imipenem
35. Which of the following are causes of inheritable mutations in bacteria?
A. Mistakes during translation of mRNA.
B. Mistakes during DNA replication.
C. Mistakes during transcription of mRNA.
D. All of the above.
E. None of the above.
36. Single base changes in an essential gene encoding one of the subunits of RNA polymerase
result in resistance to the antibiotic rifampin. Resistance to this antibiotic arises:
A. Any time the bacteria are grown, irrespective of the growth medium.
B. Only when bacteria are grown in media containing the antibiotic.
C. Only when bacteria are grown in rich media instead of minimal-salts-glucosemedium.
D. Only in bacterial cultures after they have reached stationary phase.
E. None of the above.
37. Which of the following are likely causes for resistance to antibiotics in Mycobacteria
that cause tuberculosis?
A. Deletion of the gene encoding an enzyme that activates the antibiotics into a
lethal form.
B. Antibiotic resistance of enzymes that link together the mycolic acid waxy outer
wall of these bacteria.
C. Increased degradation of enzymes that break down antibiotics.
D. Decreased permeability of the cellular inner membrane to the antibiotics.
E. All of the above.
38. Which of the following events would be the least catastrophic kind of mutation in a gene.
A. A two base pair insertion that causes a frameshift mutation.
B. A single base pair change (missense) mutation that replaces a basic amino acid
with an acidic amino acid.
C. Insertion of a transposon at the beginning of.the reading frame.
D. A single base pair change (missense) mutation that replaces an aliphatic neutral
amino acid with another aliphatic neutral amino acid.
E. A large deletion of the gene.
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39. The bacteriophage P1 packages random phage-genome-sized pieces of bacterial DNA
into phage heads and thereby allows transfer of pieces of the bacterial chromosomal
DNA between bacteria. This process is called:
A. Generalized transduction
B. Nongeneral transposition
C. Specialized transduction
D. High-frequency recombination
E. Reverse conjugation
40. Which of the following is contained in all plasmids, irrespective of size or source?
A. Genes that impart antibiotic resistance to bacterial cells.
B. An autonomous origin of replication.
C. The tra genes that allow conjugation. D. Genes that allow bacterial hosts to act as pathogens to mammalian cells.
E_ All of the above.
41. You heard, in class, about the luciferase transducing phage approach to gene transfer
in M. tuberculosis. Now, you want to apply this same approach to a completely
different, unrelated bacterial species. What is the first step that you would take?
A. The general approach cannot be applied to other bacterial species, and there is
no first step to take.
B. Simply infect the new bacterial species with the luciferase phage already constructed
for M. tuberculosis and perform the bioluminescent assay in the same way
C. 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.
D. Mix together M tuberculosis luciferase phage and temperate phage specific for
the new bacterial species and infect the new bacterial species, then perform the
bioluminescent assay in the same way.
42. Transformation is the genetic process by which:
A. Bacteriophage attach to bacterial cells.
B. Pieces of free DNA or free plasmids are taken up by bacterial cells.
C. Bacterial genes acquire mutations and variants.
D. Bacterial DNA is carried by bacteriophage between different bacteria.
E. None of the above.
MATCHING:
Choose the best answer. Answers may be used once, more than once, or not at all.
Questions 43-44: Match the following mechanisms with the best choice of antibiotic:
A. Aminoglycosides (or tetracyclines, erythromycin, clindamycin)
B. Fluoroquinolones (e.g., ciprofloxacin)
C. Rifampin
D. Sulfonamides or trimethoprim
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43. _____ Interference with protein synthesis.
44. _____ Interference with folic acid synthesis
Questions 45-46: Match the following statements to the best choice of bacterium.
A. Erysipelothrix rhusiopathiae
B. Listeria monocytogenes
C. Corynebacterium diphtheriae
45. _____Additional epidemiologic study (i.e. testing members of the household)
is not necessary subsequent to diagnosis of a patient infected with this
organism.
46. _____This organism is not known to cause cutaneous infection.
Questions 47-50: Choose the best match for the mechanisms controlling normal flora in these
organs:
A. Mucociliary action
B. low pH
C. Peristalsis
D. Antibody to normal flora
47. _____ Stomach
48. _____ Small intestine (jejunum, ileum)
49. _____ Lower respiratory tract
50. _____ Vagina, during reproductive years
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ANSWERS:
25. A
26. D
27. A
28. C
29. C
30. B
31. B
32. C
33. B
34. A
35. B
36. A
37. B
38. D
39. A
40. B
41. C
42. B
43. A
44. D
45. A
46. B
47. B
48. C
49. A
50. B
1. C
2. D
3. C
4. A
5. B
6. C
7. D
8. B
9. C
10. C
11. A
12. C
13. C
14. D
15. E
16. B
17. A
18. A
19. B
20. B
21. A
22. A
23. C
24. E
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