microbiology an introduction test bank

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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.

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Which of the following diseases is not caused by enteroviruses?

  • A. Myocarditis
  • B. Infectious mononucleosis
  • C. Herpangina
  • D. Boston Exanthema
Correct Answer: B

Rationale: Answer B, Infectious mononucleosis, is not caused by enteroviruses. Infectious mononucleosis is primarily caused by the Epstein-Barr virus, a member of the herpesvirus family, not by enteroviruses. Enteroviruses are known to cause diseases such as myocarditis, herpangina, and Boston exanthema. Therefore, B is the correct answer. Myocarditis, herpangina, and Boston exanthema can all be caused by enteroviruses, making choices A, C, and D incorrect, respectively.

For filoviruses is true that:

  • A. They are the most common cause of gastroenteritis
  • B. They can be investigated in specifically equipped laboratories with a high level of biological protection
  • C. They are widespread
  • D. Mass immunization for specific prophylaxis is used in some countries
Correct Answer: B

Rationale: The correct answer is B because filoviruses, such as Ebola virus, require investigation in specifically equipped laboratories with high biological protection due to their high pathogenicity and risk of transmission. This is essential for ensuring the safety of researchers and preventing outbreaks.

A: This is incorrect as filoviruses are not the most common cause of gastroenteritis; they primarily cause severe hemorrhagic fevers.
C: Filoviruses are not widespread; they are typically confined to specific regions during outbreaks.
D: Mass immunization is not used for filoviruses as there is no established vaccine for general prophylaxis.

A persistent infection that is not lytic but productive is called a __________ infection.

  • A. chronic
  • B. latent
  • C. slow
  • D. transforming
Correct Answer: A

Rationale: The correct answer is A: chronic. A persistent infection that is not lytic but productive is characterized by ongoing viral replication without cell lysis. This type of infection is referred to as chronic, as it persists over an extended period. Latent infections involve periods of dormancy with intermittent reactivation. Slow infections typically have a prolonged incubation period before causing symptoms. Transforming infections lead to permanent alterations in host cell behavior. The key distinction for this question is the continuous viral replication without cell destruction, which aligns with the definition of a chronic infection.

Bacteriophages are:

  • A. White blood cells that kill bacteria
  • B. Bacteria that invade other bacteria
  • C. Viruses that infect bacteria
  • D. Bacteria that infect fungi
Correct Answer: C

Rationale: The correct answer is C: Bacteriophages are viruses that infect bacteria. Firstly, bacteriophages are viruses, not white blood cells or bacteria. They specifically target and infect bacteria, not fungi. This is known as a bacteriophage cycle where the virus injects its genetic material into the bacterial cell to replicate and eventually lyse the cell. This process is specific to bacteria and distinguishes bacteriophages from other microorganisms. Therefore, the correct answer is C as it accurately describes the nature and function of bacteriophages.

The primary target of beta-lactam antibiotics is:

  • A. protein synthesis
  • B. DNA replication
  • C. cell wall synthesis
  • D. folic acid synthesis
Correct Answer: C

Rationale: The primary target of beta-lactam antibiotics is cell wall synthesis. These antibiotics inhibit enzymes called penicillin-binding proteins, which are essential for building the bacterial cell wall. By disrupting cell wall synthesis, beta-lactam antibiotics weaken the cell wall, leading to bacterial cell lysis and death. Protein synthesis (Choice A), DNA replication (Choice B), and folic acid synthesis (Choice D) are not directly targeted by beta-lactam antibiotics, making them incorrect choices.

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