microbiology chapter 10 test bank

microbiology chapter 10 test bank Related

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During a microscopy session, spiral-shaped bacteria with loose coils and pointed ends were observed in a blood smear. What is the most likely diagnosis?

  • A. Syphilis
  • B. Leptospirosis
  • C. Relapsing fever
  • D. Lyme disease
Correct Answer: B

Rationale: The correct answer is B: Leptospirosis. Spiral-shaped bacteria with loose coils and pointed ends are characteristic of Leptospira interrogans, the causative agent of Leptospirosis. This bacterium is typically found in contaminated water or soil and can infect humans through contact with infected animals or water.

Syphilis (Choice A) is caused by the spirochete Treponema pallidum, which has a more tightly coiled shape and does not typically appear loose or pointed. Relapsing fever (Choice C) is caused by Borrelia species, which are also spirochetes but do not have the loose coils and pointed ends described. Lyme disease (Choice D) is caused by Borrelia burgdorferi, which, like Relapsing fever, does not match the morphology described.

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What are the structural units of nucleic acids?

  • A. nucleosides
  • B. histones
  • C. nucleotides
  • D. n-bases
Correct Answer: C

Rationale: The correct answer is C: nucleotides. Nucleotides are the structural units of nucleic acids, consisting of a nitrogenous base, a sugar molecule, and a phosphate group. The nitrogenous base can be adenine, thymine, cytosine, guanine, or uracil. Histones (B) are proteins that DNA wraps around in chromosomes, not structural units of nucleic acids. Nucleosides (A) are composed of a nitrogenous base and a sugar molecule but lack the phosphate group present in nucleotides. N-bases (D) is not a recognized term in biology and does not accurately describe the structural units of nucleic acids.

Tularemia is most often a:

  • A. Anthroponosis
  • B. Zoonosis
  • C. Sapronosis
  • D. There is no correct answer
Correct Answer: B

Rationale: The correct answer is B: Zoonosis. Tularemia is primarily a zoonotic disease, meaning it is transmitted from animals to humans. The bacterium that causes tularemia, Francisella tularensis, commonly infects animals like rabbits, rodents, and ticks, which serve as reservoir hosts. Humans can get infected through direct contact with infected animals, insect bites, or contaminated water or soil. This zoonotic nature of tularemia distinguishes it from anthroponosis (A), which is transmitted only between humans, and sapronosis (C), which is transmitted through non-living environmental sources. Choice D is incorrect because there is a correct answer, which is zoonosis.

A patient presented with an abscess caused by Gram-positive cocci in clusters, catalase-positive and coagulase-positive. What is the causative agent?

  • A. Staphylococcus aureus
  • B. Streptococcus pyogenes
  • C. Enterococcus faecalis
  • D. Micrococcus luteus
Correct Answer: A

Rationale: Rationale:
1. Gram-positive cocci in clusters point to Staphylococcus or Micrococcus.
2. Catalase-positive eliminates Streptococcus.
3. Coagulase-positive distinguishes Staphylococcus aureus.
4. Thus, the causative agent is Staphylococcus aureus.

Summary:
- B: Streptococcus pyogenes is catalase-negative.
- C: Enterococcus faecalis is catalase-negative.
- D: Micrococcus luteus is catalase-positive but coagulase-negative.

Examination of a man revealed a protozoan disease that affected brain and caused vision loss. Blood analysis revealed unicellular half-moon-shaped organisms with pointed end. The causative agent of this disease is:

  • A. Toxoplasma B.Leishmania C.Lamblia D.Amoeba E.Trichmonad
Correct Answer: A

Rationale: The correct answer is A: Toxoplasma. Toxoplasma gondii is a protozoan parasite that can infect the brain and cause vision loss. The description of half-moon-shaped organisms with a pointed end matches the appearance of Toxoplasma under the microscope. Toxoplasma is known to cause a condition called toxoplasmosis, which can lead to neurological symptoms such as vision loss. Leishmania, Lamblia, Amoeba, and Trichomonad are not known to cause brain infections or vision loss, making them incorrect choices.

All of the following infections may recur during pregnancy except:

  • A. Epstein-Barr virus infections
  • B. herpes simplex virus infections
  • C. streptococcal infections
  • D. polyomavirus infections
Correct Answer: D

Rationale: The correct answer is D: polyomavirus infections. Polyomavirus infections do not typically recur during pregnancy because once the virus infects the body, it remains latent without causing recurrent infections. In contrast, choices A, B, and C can recur during pregnancy due to their ability to reactivate from latency or reinfect the host. Epstein-Barr virus infections (choice A) can lead to infectious mononucleosis, herpes simplex virus infections (choice B) can cause recurrent genital or oral herpes outbreaks, and streptococcal infections (choice C) can result in recurrent throat or skin infections.