Microbiology Chapter 13 Test Bank

Microbiology Chapter 13 Test Bank Related

Review Microbiology Chapter 13 Test Bank related questions and content

A 10 year old child was subjected to Mantoux test (with tuberculin). 48 hours later a papule up to 8 mm in diameter appeared on the site of tuberculin injection. What type of hyperesponsiveness reaction has developed after tuberculin injection?

  • A. Hyperresponsiveness reaction type IV
  • B. Reaction of Arthus phenomenon type
  • C. Reaction of serum sickness type
  • D. Atopic reaction
Correct Answer: A

Rationale: The correct answer is A: Hyperresponsiveness reaction type IV. This type of reaction, also known as delayed-type hypersensitivity, is characterized by the activation of T lymphocytes and macrophages, leading to inflammation at the site of antigen exposure. In the case of the Mantoux test, the appearance of a papule 48 hours later indicates a delayed hypersensitivity reaction mediated by T cells.

Choice B: Reaction of Arthus phenomenon type is incorrect as this type of reaction involves immune complexes forming in the blood vessels leading to tissue damage, which is not the mechanism seen in the Mantoux test reaction.

Choice C: Reaction of serum sickness type is incorrect as this type of reaction involves the formation of immune complexes in the blood leading to systemic symptoms like fever, rash, and joint pain, which is not typically seen in the Mantoux test reaction.

Choice D: Atopic reaction is incorrect as atopic reactions involve IgE antibodies and mast cell degranulation, which are not the mechanisms

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Which bacterium is known for producing an exotoxin that causes severe diarrhea?

  • A. Clostridium tetani
  • B. Clostridium botulinum
  • C. Vibrio cholerae
  • D. Shigella dysenteriae
Correct Answer: C

Rationale: Rationale:
1. Vibrio cholerae produces cholera toxin causing severe diarrhea.
2. Clostridium tetani causes tetanus, not diarrhea.
3. Clostridium botulinum causes botulism, not diarrhea.
4. Shigella dysenteriae causes dysentery, not typical diarrhea.

Summary:
A: Incorrect, causes tetanus.
B: Incorrect, causes botulism.
C: Correct, produces cholera toxin causing severe diarrhea.
D: Incorrect, causes dysentery.

Bacteriological laboratory examines canned meat whether it contains botulinum toxin. For this purpose an extract of test specimen and antitoxic antibotulinic serum of A, B, E types were introduced to a group of mice under examination; a control group of mice got the extract without antibotulinic serum. What serological reaction was applied?

  • A. Neutralization
  • B. Precipitation
  • C. Complement binding
  • D. Double immune diffusion
Correct Answer: A

Rationale: The correct answer is A: Neutralization. In this scenario, the antibotulinic serum of types A, B, and E were introduced to neutralize the botulinum toxin in the test specimen. The serological reaction applied here involves the neutralization of the toxin by the specific antibodies present in the serum. This process prevents the toxin from causing harm to the mice.

Summary of other choices:
B: Precipitation - This involves the formation of insoluble complexes between antigen and antibody, not the specific neutralization seen in this case.
C: Complement binding - This involves activation of the complement system leading to cell lysis, not the direct neutralization of toxin.
D: Double immune diffusion - This technique is used to determine the presence of specific antibodies or antigens based on their diffusion patterns, not the neutralization of toxin as seen in this scenario.

Which of the following bacteria is known for causing dental caries (cavities)?

  • A. Streptococcus mutans
  • B. Streptococcus pneumoniae
  • C. Bacillus anthracis
  • D. Clostridium botulinum
Correct Answer: A

Rationale: Step 1: Streptococcus mutans is known for its ability to produce acids that contribute to the demineralization of tooth enamel, leading to dental caries.
Step 2: Streptococcus pneumoniae is a common cause of respiratory infections, not dental caries.
Step 3: Bacillus anthracis causes anthrax, a serious bacterial infection, not dental caries.
Step 4: Clostridium botulinum causes botulism, a severe form of food poisoning, not dental caries.
Summary: Streptococcus mutans is the correct answer as it is specifically associated with causing dental caries, while the other choices are linked to different diseases.

Which structure protects bacteria from phagocytosis?

  • A. Flagella
  • B. Capsule
  • C. Endospore
  • D. Pili
Correct Answer: B

Rationale: The correct answer is B: Capsule. Capsules are a protective layer outside the bacterial cell wall that helps bacteria evade phagocytosis by immune cells. The capsule inhibits phagocytic cells from engulfing the bacteria, making it difficult for them to be recognized and destroyed.

A: Flagella - Flagella are not involved in protecting bacteria from phagocytosis. They are responsible for bacterial movement.
C: Endospore - Endospores are dormant, resistant structures formed by some bacteria in response to harsh conditions. They do not directly protect against phagocytosis.
D: Pili - Pili are hair-like structures used for adhesion and conjugation, not for protection against phagocytosis.

For measles virus is true that:

  • A. There is no outer membrane
  • B. Contains singles-stranded RNA with negative polarity
  • C. Belongs to family Togaviridae
  • D. Cannot be grown on cell cultures
Correct Answer: B

Rationale: The correct answer is B: Contains single-stranded RNA with negative polarity. Measles virus is an enveloped virus with a single-stranded RNA genome that is negative-sense. This means it must first be transcribed into positive-sense RNA before it can be translated. Choice A is incorrect as the measles virus does have an outer envelope. Choice C is incorrect as measles virus belongs to the family Paramyxoviridae, not Togaviridae. Choice D is incorrect as measles virus can be grown on cell cultures, specifically on Vero cells.

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