free microbiology test bank questions pdf

free microbiology test bank questions pdf Related

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Which bacteria produce exotoxins that affect the nervous system?

  • A. Clostridium botulinum and Clostridium tetani
  • B. Escherichia coli and Salmonella
  • C. Bacillus anthracis and Listeria monocytogenes
  • D. Pseudomonas aeruginosa and Staphylococcus aureus
Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum and Clostridium tetani. Both bacteria produce exotoxins that affect the nervous system. Clostridium botulinum produces botulinum toxin, causing botulism, leading to muscle paralysis. Clostridium tetani produces tetanospasmin, causing tetanus, leading to muscle stiffness and spasms.

Choice B (Escherichia coli and Salmonella) are known for causing gastrointestinal infections, not specifically affecting the nervous system. Choice C (Bacillus anthracis and Listeria monocytogenes) produce toxins that primarily affect other body systems, not the nervous system. Choice D (Pseudomonas aeruginosa and Staphylococcus aureus) are associated with skin and respiratory infections, not neurological effects.

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The structure used for bacterial motility is:

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

Rationale: The correct answer is C: Flagella. Flagella are the structures used for bacterial motility, allowing bacteria to move towards or away from stimuli. They are long, whip-like appendages that rotate to propel the bacteria. Fimbriae (A) are short, hair-like structures used for attachment, not movement. Capsules (B) are protective layers surrounding bacteria. Pili (D) are used for adherence and conjugation, not motility. In summary, flagella are specifically designed for bacterial movement, making them the correct choice.

Microscopy of a smear obtained from a patient with acute purulent periostitis revealed gram-positive bacteria arranged in clusters resembling bunch of grapes. What microorganisms is this morphology typical for?

  • A. Staphylococci
  • B. Sarcina
  • C. Tetracocci
  • D. Candida fungi
Correct Answer: A

Rationale: Rationale:
Staphylococci are gram-positive bacteria that typically arrange in clusters resembling a bunch of grapes. This characteristic morphology is specific to staphylococci due to their division pattern. Sarcina, Tetracocci, and Candida fungi do not exhibit this clustering pattern. Staphylococci are commonly associated with purulent infections, making them the most likely microorganisms in this scenario.

A child with diarrhea had stool microscopy revealing cysts with four nuclei. What is the most likely causative agent?

  • A. Entamoeba histolytica
  • B. Giardia lamblia
  • C. Balantidium coli
  • D. Trichomonas hominis
Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This pathogen is known to cause amoebic dysentery, characterized by diarrhea with bloody or mucoid stools. The presence of cysts with four nuclei in the stool microscopy is a characteristic feature of Entamoeba histolytica. Other choices are incorrect because Giardia lamblia typically presents with binucleate cysts, Balantidium coli is a ciliated protozoan, and Trichomonas hominis is a non-pathogenic parasite found in the human intestine.

The causative agent of tuberculosis is:

  • A. Mycobacterium leprae
  • B. Mycobacterium tuberculosis
  • C. Bacillus anthracis
  • D. Staphylococcus aureus
Correct Answer: B

Rationale: The correct answer is B: Mycobacterium tuberculosis. Mycobacterium tuberculosis is the causative agent of tuberculosis, as it specifically infects the lungs and can spread to other parts of the body. Mycobacterium leprae (Choice A) causes leprosy, not tuberculosis. Bacillus anthracis (Choice C) causes anthrax, not tuberculosis. Staphylococcus aureus (Choice D) is a common bacterium known for causing skin infections, not tuberculosis. Therefore, Mycobacterium tuberculosis is the correct answer for the causative agent of tuberculosis.

How would you interpret the study results?

  • A. Water is safe to be consumed
  • B. Water is of doubtful quality
  • C. Water is of highly doubtful quality
  • D. Water is contaminated
Correct Answer: D

Rationale: Step-by-step rationale:
1. The study results indicate water contamination.
2. Contaminated water poses health risks.
3. Therefore, the correct interpretation is that water is contaminated.
Summary:
- Choice A is incorrect as safety is not confirmed.
- Choice B is too mild given the severity of contamination.
- Choice C is also incorrect, as it does not accurately reflect the study findings.

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