microbiology chapter 11 test bank

microbiology chapter 11 test bank Related

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Examination of duodenal contents revealed some pyriform protozoa with twin nuclei and four pairs of flagella. There were two supporting filaments between the nuclei and a suctorial disc on the ventral side. What representative of protozoa was revealed in this patient?

  • A. Lamblia
  • B. Toxoplasma
  • C. Leishmania
  • D. Intestinal trichomonad
Correct Answer: A

Rationale: Rationale for Correct Answer A (Lamblia):
1. Pyriform protozoa with twin nuclei, four pairs of flagella, and a suctorial disc match the characteristics of Giardia lamblia.
2. The presence of two supporting filaments between the nuclei is a unique feature of Giardia lamblia.
3. Giardia lamblia is known to infect the duodenum and cause symptoms such as diarrhea and abdominal pain.

Summary of Incorrect Choices:
B: Toxoplasma - Toxoplasma gondii is not characterized by four pairs of flagella or supporting filaments in the nuclei.
C: Leishmania - Leishmania species do not typically have the described morphology or location in the duodenum.
D: Intestinal trichomonad - Intestinal trichomonads do not exhibit the specific features mentioned in the question, such as twin nuclei and supporting filaments.

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Which of the following best describes bacterial conjugation?

  • A. Transfer of DNA through a sex pilus
  • B. Uptake of free DNA from the environment
  • C. Transfer of DNA by bacteriophages
  • D. Binary fission
Correct Answer: A

Rationale: The correct answer is A because bacterial conjugation involves the transfer of genetic material through a sex pilus from a donor bacterium to a recipient bacterium. This process allows for the exchange of genetic material and can lead to increased genetic diversity within bacterial populations.

Option B is incorrect because the uptake of free DNA from the environment is known as transformation, not conjugation. Option C is incorrect as transfer of DNA by bacteriophages is called transduction, not conjugation. Option D is incorrect because binary fission is a form of asexual reproduction in bacteria, not a mechanism for genetic exchange.

Which bacteria is known for causing the disease tetanus?

  • A. Clostridium tetani
  • B. Clostridium perfringens
  • C. Neisseria gonorrhoeae
  • D. Bacillus anthracis
Correct Answer: A

Rationale: Step-by-step rationale for why A is correct:
1. Clostridium tetani is known to produce tetanus toxin.
2. The tetanus toxin causes muscle rigidity and spasms characteristic of tetanus.
3. Clostridium perfringens is associated with gas gangrene, not tetanus.
4. Neisseria gonorrhoeae causes gonorrhea, not tetanus.
5. Bacillus anthracis causes anthrax, not tetanus.

In summary, Clostridium tetani is the correct answer as it is specifically associated with causing tetanus, while the other choices are associated with different diseases.

A 4 year old child had Mantoux test. 60 hours after tuberculin introduction a focal skin hardening and redness 15 mm in diameter appeared. It was regarded as positive test. What type of hypersensitivity reaction is this test based upon?

  • A. Delayed-type hypersensitivity
  • B. Immune complex-mediated hypersensitivity
  • C. Complement-mediated cytotoxic hypersensitivity
  • D. Immediate hypersensitivity
Correct Answer: A

Rationale: The correct answer is A: Delayed-type hypersensitivity. The Mantoux test is a type IV hypersensitivity reaction, which is also known as delayed-type hypersensitivity. This reaction typically occurs 48-72 hours after exposure to an antigen, such as tuberculin in this case. The focal skin hardening and redness that appeared 60 hours after tuberculin introduction align with the timeline and characteristics of a delayed-type hypersensitivity reaction.

Summary:
- Choice A (Delayed-type hypersensitivity): Correct, as explained above.
- Choice B (Immune complex-mediated hypersensitivity): Incorrect, as this reaction involves immune complexes and typically presents with tissue damage and inflammation.
- Choice C (Complement-mediated cytotoxic hypersensitivity): Incorrect, as this reaction involves the activation of complement proteins leading to cell lysis.
- Choice D (Immediate hypersensitivity): Incorrect, as this reaction, such as in allergies, occurs within minutes to hours of exposure to an antigen and involves IgE-mediated mast

Enzymes used in ELISA are those except:

  • A. Î’-lactamase
  • B. Alkaline phosphatase
  • C. Horseradish peroxidase
  • D. Î’- galactosidase
Correct Answer: A

Rationale: The correct answer is A: Β-lactamase. In ELISA, enzymes like alkaline phosphatase, horseradish peroxidase, and Β-galactosidase are commonly used as labels to detect the presence of specific molecules. Β-lactamase is not typically used in ELISA as it is an enzyme used to hydrolyze β-lactam antibiotics. Therefore, it does not serve the purpose of detecting specific molecules in ELISA. Alkaline phosphatase, horseradish peroxidase, and Β-galactosidase are preferred enzymes in ELISA due to their ability to produce a detectable signal when bound to specific molecules.

Streptococcus pyogenes releases:

  • A. Enterotoxin
  • B. Streptolysin
  • C. Staphylocoagulase
  • D. None of the above
Correct Answer: B

Rationale: The correct answer is B: Streptolysin. Streptolysin is a toxin released by Streptococcus pyogenes that causes lysis of red blood cells and contributes to the pathogenicity of the bacteria. Enterotoxin (Choice A) is typically produced by Staphylococcus aureus, not Streptococcus pyogenes. Staphylocoagulase (Choice C) is an enzyme produced by Staphylococcus aureus to promote blood clot formation and is not associated with Streptococcus pyogenes. Therefore, the correct answer is B as Streptolysin is the toxin released by Streptococcus pyogenes.

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