MICROBIOLOGY EXAM II
CODE 2
PART I - LABORATORY EXAM, QUESTIONS 1-50
TRUE OR FALSE
Choose the best possible answer. A= True; B= False
Questions 1-3
A specimen collected from a deep wound infection is cultured, in an air incubator, on 596 sheep
blood agar. After 24 hrs, the clinical laboratory reports "no growth". The original Gram stain of
the specimen, revealed many box car shaped gram-positive rods. No spores were seen.
1. ______ This bacteria is usually susceptible to Penicillin.
2. ______ This bacteria produces beta-lactamase.
3. ______ This organism is a strict anaerobe, and should have been incubated in the absence of
oxygen.
Questions 4-8
4. ______ In the Gram stain, crystal violet is the primary stain.
5. ______ Propionibacterium acnes is a common contaminant of anaerobic blood cultures.
6. ______ The coagulase test detects the ability of bacteria to convert fibrinogen to fibrin.
7. ______ Antiseptics are used primarily to clean endoscopes.
8. ______ Sterilants can kill bacterial spores.
MATCHING
Match the BEST possible answer with each question. Answers may be used once, more than
once, or not at all.
Questions 9-15
a) Gram negative, rod-shaped
b) Gram positive, spherical-shaped
c) Gram negative diplococci
d) Gram positive, rod-shaped
e) None of the above
9. Escherichia coli
10. Staphylococcus epidermidis
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11. Bacteroides fragilis
12. Neisseria meningitidis
13. Streptococcus pyogenes
14. Klebsiella pneumoniae
15. Bacillus subtilis
Questions 16-20
Choose the most appropriate answer.
a) Bile salts
b) Phenylethyl alcohol
c) Catalase
d) Coagulase
e) CAMP test
16. Added to Blood agar to select gram-positive bacteria agar
17. Used to specifically identify Group B Streptococci
18. Added to MacConkey agar to select gram-negative bacteria
19. Distinguishes Staphylococcus from Streptococcus
20. Used to differentiate S. aureus from other staphylococci
SIMPLE COMPLETIONS
Give the BEST answer for the following questions:
21. A gram-positive coccus, that occurs in pairs or short chains, and produces mucoid, alphahemolytic colonies on 5% sheep blood agar is most likely:
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Enterococcus faecalis
d) Staphylococcus aureus
e) Streptococcus pneumoniae
22. In the laboratory diagnosis of enteric pathogens, to discriminate Salmonella and Shigella,
from other Enterobacteriaceae, the screening procedure includes testing for their inability to:
a) Ferment glucose
b) Ferment 1uctose.
c) Produce cytochrome oxidase
d) Reduce nitrates
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23. The presence of squamous epithelial cells in a sputum sample suggests that:
a) Saliva contaminated the specimen, making interpretation difficult.
b) The specimen was collected properly.
c) The specimen will have a value of Q3.
d) The specimen contains microorganisms from the lower respiratory tract.
24. Which of the following are advantages of direct, bacterial antigen detection tests over
bacterial culture?
a) In bacterial antigen detection tests, results are obtained rapidly.
b) In bacterial antigen detection tests, non-culturable microorganisms can be identified.
c) Bacterial antigen tests can detect live, as well as dead organisms.
d) All the above statements are true
25. A greenish discoloration in the agar surrounding and beneath the colony on a 5% sheep blood
agar plate is called:
a) Alpha-hemolysis
b) Beta-hemolysis
c) Gamma-hemolysis
d) Delta-hemolysis
e) No-hemolysis
26. Which of the following statements is incorrect?
a) Mycobacterium tuberculosis is acid-fast.
b) Streptococcus pneumoniae is Optochin susceptible.
c). Staphylococcus epidermidis is coagulase negative.
d).Escherichia coli grows on MacConkey agar.
e) Salmonella does not produce H2S.
27. All of the following specimens must be sent to the laboratory immediately EXCEPT:
a) Cervical exudate
b) Urine
c) Rectal swabs
d) Spinal fluid
e) Throat swabs
28. When isolated from clinical specimens, some bacteria do not require antibiotic susceptibility
testing, because they are predictably susceptible to a variety of antibiotics. This is TRUE of
which of the following?
a) E. coli
b) S. aureus
c) Most obligate anaerobes
d) Enterococci
e) Klebsiella
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29. According to Dr. Bartlett, the ideal specimen to detect lower respiratory tract infections
should contain:
a) >25 neutrophils and <10 squamous cells/low power field
b) >25 neutrophils and >25 squamous cells/low power field
c) <25 neutrophils and <25 squamous.cells/low power field
d) >25 bacteria/low power field
e) A ratio of squamous cells to neutrophils of 5:1
30. All of the following include uses of the Gram stain EXCEPT:
a) To determine bacterial morphology
b) To presumptively identify a pathogenic organism
c) To observe inflammatory cells in clinical specimens
d) To evaluate sputum before culture
e) To identify Group A Streptococcus on a throat sample
31. The following are important considerations when selecting and collecting a specimen for
microbiologica1 examination except:
a) Specimen should be representative of the disease
b) Specimen should be collected during acute phase of the disease
c) Specimen must be transported promptly to the laboratory
d) Specimen should be collected after therapy
32. A smear of spinal fluid from a 5 year old child with meningitis reveals the presence of gram
negative, pleomorphic rods. The most probable etiologic agent of this infection is:
a) Group B streptococci
b) Group A streptococci
c) Haemophilus influenzae
d) Escherichia coli
e) Streptococcus pneumoniae
33. The ideal specimen to collect for microbiological analysis during the first week of Typhoid
fever is:
a) Blood
b) Stool
c) Urine
d) Sputum
e) Spinal fluid
34. The "India Ink" technique is used for the visualization of:
a) Encapsulated microorganisms
b) Motile organisms
c) Non-motile organisms
d) Sporulated bacteria
e) Acid-fast bacteria
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35. The most common contaminants of blood cultures:
a) Gram-negative rods
b) Coagulase-negative staphylococci
c) Staphylococcus aureus
c) Anaerobes
e) None of the above
36. The Beta-lactamase test is not needed for:
a) Haemophilus influenzae
b) Streptococcus pneumoniae
c) Staphylococcus aureus
d) Streptococcus pyo ecnes
e) Neisseria gonorrhoeae
37. Your male patient has an urethral discharge. The Gram-stain reveals the presence of
intracellular, gram-negative cocci. This is highly diagnostic of:
a) Candidiasis
b) Trichomoniasis
c) Gonorrhoea
d) Infection by Chlamydia
e) Syphilis
38. Non-bacterial microorganisms that can be identified using the Acid-Fast stain include:
a) Trichomonas
b) Giardia
c) Cryptosporidium
d) Entamoeba
39. The obligate anaerobe most frequently isolated from clinical specimens is:
a)Clostridium perfringens
b) Bacteroides fragilis
c) Clostridium tetani
d) Clostridium botulinum
e) Fusobacterium nucleatum
40. Candida albicans can be most rapidly identified from a cervical exudate using:
a) A latex agglutination test
b) A Gram stain
c) A "wet prep" with 10% KOH
d) An anaerobic culture
e) A "wet prep" with India ink
41. The minimum amount of antibiotic that inhibits bacterial growth in a broth dilution test is
known as the:
a) MIC
b) MBC
c) MMC
d) NBC
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Questions 42-43
Your friend has just returned from a week in Mexico where he had a great time. However, he has
come down with watery diarrhea with blood and mucus, fever and abdominal cramps. The
clinical laboratory has isolated a gram-negative, non-lactose fermenter, non-motile rod from his
stool.
42. This organism is most likely:
a) Giardia lamblia
b) Salmonella typhi
c) Klebsiella pneumoniae
d) Entamoeba histolytica
e) Shigella sonnei
43. Normal fecal flora expected to be found in this patient's stool culture should include all the
following, EXCEPT:
a) Klebsiella
b) Escherichia
c) Yersinia
d) Enterobacter
44. A 39 year old female comes to the Family Practice Clinic complaining of pain and burning
on urination. A urine specimen is sent to the laboratory for culture. A preliminary report is sent
to you, reporting that an organism is growing on Blood agar and PEA blood agar plates, but not
on McConkey agar. The responsible microorganism is most likely:
a) A gram-negative rod
b) An acid-fast bacteria
c) A gram-positive cocci
d) A fungi
45. Which of the following organisms is most often implicated in urinary tract infections?
a) Enterococcus faecalis
b) Staphylococcus saprophyticus
c) Escherichia coli
d) Klebsiella pneumoniae
e) Proteus mirabilis
46. How many microorganisms per milliliter must be present in a urine sample, to be considered
indicative of bacteriuria?
a) >102 CFU/ml
b) >103 CFU/ml
c) >104 CFU/ml
d) >105 CFU/ml
47. Regarding Neisseria gonorrhoeae
a) It is sensitive to desiccation
b) It is cythocrome oxidase positive
c) It grows on Chocolate agar or Thayer-Martin medium
d) It requires approximately 5-10% CO2 to grow
e) All of the above statements are true
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48. Which of the following are predisposing factors for urinary tract infections?
a) Urinary tract catheterization
b) Prostatic hypertrophy
c) Presence of kidney stones
d) All the above statements are correct
e) None of the above statements is correct
49. Which of the following tests would be most useful in the rapid differentiation between
bacterial and tuberculous meningitis?
a) Tuberculin test
b) CSF culture on-Lowenstein-Jensen agar
c) Acid-fast stain of spinal fluid
d) Guinea pig inoculation
e) CSF culture on blood agar plate
50. Susceptibility to bacitracin differentiates:
a) Streptococcus pneumoniae from Staphylococcus aureus
b) Streptococcus pyogenes from Streptococcus agalactiae
c) Streptococcus pneumoniae from Viridans Group streptococci
d) Staphylococcus aureus from Staphylococcus epidermidis
e) Enterococcus faecalis from Enterococcus durans
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ANSWERS:
1. A
2. B
3. A
4. A
5. A
6. A
7. B
8. A
9. A
10. B
11. A
12. C
13. B
14. A
15. D
16. B
17. E
18. A
19. C
20. D
21. E
22. B
23. A
24. D
25. A
26. E
27. E
28. C
29. A
30. E
31. D
32. C
33. A
34. A
35. B
36. D
37. C
38. C
39. B
40. C
41. A
42. E
43. C
44. C
45. C
46. D
47. E
48. D
49. C
50. B
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