microbiology basic and clinical principles test bank

microbiology basic and clinical principles test bank Related

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A child with a persistent sore throat and fever had a smear from the throat revealing rod-shaped bacteria with dark blue polar granules. What is the likely causative agent?

  • A. Corynebacterium diphtheriae
  • B. Streptococcus pyogenes
  • C. Haemophilus influenzae
  • D. Klebsiella pneumoniae
Correct Answer: A

Rationale: The correct answer is A: Corynebacterium diphtheriae. The presence of rod-shaped bacteria with dark blue polar granules suggests the presence of Corynebacterium diphtheriae, the causative agent of diphtheria. This bacterium is known for causing sore throat and fever, and the characteristic appearance on smear helps identify it. Streptococcus pyogenes (Choice B) typically appears as chains of cocci and is associated with strep throat. Haemophilus influenzae (Choice C) is a small, pleomorphic Gram-negative coccobacillus and is more commonly associated with respiratory infections. Klebsiella pneumoniae (Choice D) is a Gram-negative bacillus and is not typically associated with sore throat and fever in children.

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The oldest fossils of prokaryotes go back __________ billion years.

  • A. 4.0 to 5.0
  • B. 3.5 to 4.0
  • C. 2.5 to 3.0
  • D. 2.2 to 2.7
Correct Answer: B

Rationale: The correct answer is B: 3.5 to 4.0 billion years. This range aligns with the oldest known fossils of prokaryotes found in ancient rocks. Fossils dating back to this time period provide evidence of early life forms on Earth. Choices A, C, and D are incorrect because they fall outside the established timeline based on scientific evidence and fossil records. A (4.0 to 5.0 billion years) is too early for the oldest prokaryote fossils, as it predates the formation of Earth's atmosphere suitable for life. C (2.5 to 3.0 billion years) and D (2.2 to 2.7 billion years) are too recent for the oldest prokaryote fossils, as life is believed to have originated much earlier.

Formic acid is a fermentation product of

  • A. Streptococcus.
  • B. Klebsiella.
  • C. Clostridium.
  • D. Actinomyces.
Correct Answer: D

Rationale: Step 1: Formic acid is produced during fermentation by Actinomyces.
Step 2: Actinomyces are known to produce organic acids like formic acid through fermentation.
Step 3: Other choices like Streptococcus, Klebsiella, and Clostridium are not typically associated with formic acid production.
Step 4: Actinomyces is the most likely candidate based on its fermentation capabilities.
Summary: Actinomyces is the correct answer because it is known to produce formic acid during fermentation, while the other choices lack this specific metabolic function.

Immunity after single vaccination against tetanus - application of tetanus toxoid is:

  • A. intense and usually life long
  • B. of limited duration, booster vaccinations are needed
  • C. infectious (non-sterile)
  • D. no correct answer
Correct Answer: B

Rationale: The correct answer is B. Immunity after a single tetanus vaccination is of limited duration, usually around 10 years. Booster vaccinations are needed to maintain protection due to waning immunity over time. Choice A is incorrect as immunity is not usually lifelong. Choice C is incorrect as tetanus toxoid is a sterile vaccine and does not cause infection. Choice D is also incorrect as there is a correct answer, which is B.

Etiological cause of bacteremia could be:

  • A. S.epidermidis, E.coli, S. aureus
  • B. P.aeruginosa, K. pneumoniae, E.coli
  • C. Resident skin diphtheroids
  • D. All of the above
Correct Answer: D

Rationale: The correct answer is D because bacteremia can be caused by a variety of bacteria including S.epidermidis, E.coli, S.aureus, P.aeruginosa, K.pneumoniae, and resident skin diphtheroids. Bacteremia refers to the presence of bacteria in the bloodstream, which can occur due to infections from various sources. Choices A and B include common bacteria known to cause bacteremia, while choice C refers to resident skin diphtheroids that can also enter the bloodstream under certain conditions. Therefore, the correct answer is D as it encompasses all the possible etiological causes of bacteremia.

Salmonellosis is caused by:

  • A. Salmonella typhi
  • B. Salmonella enteritidis
  • C. Shigella flexneri
  • D. None of the above
Correct Answer: B

Rationale: The correct answer is B: Salmonella enteritidis. Salmonellosis is typically caused by Salmonella species, with Salmonella enteritidis being one of the common culprits. Salmonella typhi causes typhoid fever, not salmonellosis. Shigella flexneri is responsible for causing shigellosis, a different bacterial infection. Choosing "None of the above" is incorrect as Salmonella enteritidis is a known cause of salmonellosis.

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