Microbiology An Introduction Test Bank

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A 45-year-old patient complains of body temperature rise up to 40oC, general weakness, headache, painfulness and spastic muscle contractions around the wound in the shin. He received this wound 5 days ago when working in his garden. He requested no medical care back then. What wound infection can be suspected?

  • A. Tetanus
  • B. Anthrax
  • C. Erysipelas
  • D. Gram-positive
Correct Answer: A

Rationale: The correct answer is A: Tetanus. The patient's symptoms of muscle contractions, fever, and wound history suggest tetanus, caused by Clostridium tetani bacteria commonly found in soil. The spastic muscle contractions around the wound are classic for tetanus due to the neurotoxin produced by the bacteria. General weakness and headache are also common symptoms.

B: Anthrax is unlikely as it presents with different symptoms such as skin lesions, respiratory symptoms, and gastrointestinal symptoms.

C: Erysipelas is characterized by red, swollen patches on the skin, not consistent with the symptoms described.

D: Gram-positive is not a specific diagnosis but a broad category of bacteria. Tetanus is caused by Clostridium tetani, which is a Gram-positive bacterium, but this choice does not provide a specific infection diagnosis.

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The net gain of ATP molecules after the breakdown of one glucose molecule in glycolysis is

  • A. 1
  • B. 2
  • C. 3
  • D. 4
Correct Answer: B

Rationale: The correct answer is B (2). During glycolysis, one glucose molecule is broken down into two molecules of pyruvate. In this process, a net gain of 2 ATP molecules is produced through substrate-level phosphorylation. Specifically, ATP is generated during the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate and during the conversion of phosphoenolpyruvate to pyruvate. The other choices are incorrect because the net gain of ATP molecules in glycolysis is not 1, 3, or 4; it is 2 based on the specific enzymatic reactions involved in the pathway.

For the specific prophylaxis of rabies it is NOT CORRECT that

  • A. Ab against rabies virus can be found 14-15 days after immunization
  • B. Reinfection is not possible
  • C. HRIG (human rabies immunoglobulin) is applied in the first few hours after possible infection
  • D. Six (5+1) doses of an inactivated vaccine are applied
Correct Answer: B

Rationale: The correct answer is B because reinfection is indeed possible with rabies virus. Step 1: Reinfection occurs if a person is exposed to the virus again after initial infection. Step 2: Once infected, the virus can remain dormant in the body and become active upon re-exposure. Step 3: Therefore, it is essential to continue preventive measures even after initial immunization. Summary: Choices A, C, and D are incorrect because antibodies develop within 14-15 days post-immunization, HRIG is administered shortly after exposure, and a specific vaccination schedule is followed for rabies prophylaxis, respectively.

A wound swab from a patient with severe tissue infection revealed Gram-positive rods in chains producing gas. The bacteria were spore-forming. What is the causative agent?

  • A. Clostridium perfringens
  • B. Bacillus anthracis
  • C. Clostridium tetani
  • D. Pseudomonas aeruginosa
Correct Answer: A

Rationale: The correct answer is A: Clostridium perfringens. This bacterium is a Gram-positive rod that forms chains and produces gas due to its ability to ferment carbohydrates. It is also spore-forming, which helps it survive harsh conditions. Clostridium perfringens is commonly associated with severe tissue infections and gas gangrene.

Choice B: Bacillus anthracis is also a spore-forming Gram-positive rod but is not typically associated with gas production or severe tissue infections.

Choice C: Clostridium tetani is a spore-forming bacterium that causes tetanus, not severe tissue infections with gas production.

Choice D: Pseudomonas aeruginosa is a Gram-negative bacterium and does not fit the description provided in the question.

Lysozyme acts on the bacterial:

  • A. cytoplasm
  • B. cell wall
  • C. nucleus
  • D. capsule
Correct Answer: B

Rationale: The correct answer is B: cell wall. Lysozyme is an enzyme that targets the cell wall of bacteria by breaking down the peptidoglycan layer, leading to bacterial cell lysis. This action disrupts the structural integrity of the bacteria, ultimately causing their death. Choices A, C, and D are incorrect because lysozyme does not target the cytoplasm, nucleus, or capsule of bacteria. The primary function of lysozyme is to act on the cell wall, making option B the correct answer in this context.

A patient presented with a painful, swollen lymph node, and bacteremia. A Gram-negative rod with a characteristic safety pin appearance was observed. What is the causative agent?

  • A. Yersinia pestis
  • B. Clostridium tetani
  • C. Brucella melitensis
  • D. Pasteurella multocida
Correct Answer: A

Rationale: Step 1: Gram-negative rod with safety pin appearance indicates bipolar staining.
Step 2: Yersinia pestis is a Gram-negative rod causing bubonic plague.
Step 3: Y. pestis has bipolar staining due to its unique F1 capsule.
Step 4: The swollen lymph node and bacteremia are consistent with bubonic plague.
Step 5: Therefore, the correct answer is A: Yersinia pestis.

Summary:
- B: Clostridium tetani causes tetanus, not characterized by a safety pin appearance.
- C: Brucella melitensis causes brucellosis, not characterized by a safety pin appearance.
- D: Pasteurella multocida causes animal bites infections, not characterized by a safety pin appearance.

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