Microbiology Basic and Clinical Principles Test Bank

Microbiology Basic and Clinical Principles Test Bank Related

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A 12-year-old boy presents with nausea, frequent repeated vomiting that first occurred after eating canned vegetables. Objectively: the patient has dry mucous membranes, muscular hypotonia, anisocoria, mydriasis, dysphagia and dysarthria. What is the most likely diagnosis?

  • A. Botulism
  • B. Shigellosis
  • C. Salmonellosis
  • D. Cholera
Correct Answer: A

Rationale: The most likely diagnosis is A: Botulism. The symptoms, such as nausea, vomiting after eating canned vegetables, dry mucous membranes, muscular hypotonia, anisocoria, mydriasis, dysphagia, and dysarthria, are classic signs of botulism poisoning. Botulism is caused by the neurotoxin produced by Clostridium botulinum bacteria found in improperly canned or preserved food. The neurotoxin affects the nervous system, leading to symptoms like those described. Shigellosis (B), Salmonellosis (C), and Cholera (D) typically present with different symptoms such as diarrhea, fever, and abdominal pain, which are not seen in this patient.

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The virulence factors of bacteria include:

  • A. size, adhesion, resistance, and mutation
  • B. colonization, invasion, toxins, and adhesion
  • C. toxins, evasion of body defenses, motility, and size
  • D. colonization, chemotaxis, fermentation, and toxins
Correct Answer: B

Rationale: Rationale: The correct answer is B because virulence factors of bacteria are characteristics that enable them to cause disease. Colonization allows bacteria to establish and multiply in the host. Invasion refers to the ability to penetrate host tissues. Toxins are substances produced by bacteria that harm the host. Adhesion is crucial for bacteria to attach to host cells.
A: Size and mutation are not typical virulence factors. Resistance is not directly related to causing disease.
C: While toxins and evasion of body defenses are correct, motility and size are not universally considered virulence factors.
D: Chemotaxis and fermentation are not primary virulence factors, unlike colonization and toxins.

What is the structure of bacterial flagella?

  • A. 9+2 microtubule arrangement
  • B. protein filaments made of flagellin
  • C. lipid bilayer
  • D. peptidoglycan layer
Correct Answer: B

Rationale: The correct answer is B: protein filaments made of flagellin. Bacterial flagella are composed of flagellin proteins arranged in helical filaments. This structure allows for movement and propulsion of bacteria.

A: 9+2 microtubule arrangement is incorrect because this structure is typically found in eukaryotic flagella, not bacterial flagella.
C: Lipid bilayer is incorrect as it is a structural component of cell membranes, not bacterial flagella.
D: Peptidoglycan layer is incorrect as it is a component of bacterial cell walls, not flagella.

Which of the following viruses belongs to family Arenaviridae?

  • A. Rabies virus
  • B. Crimean-Congo hemorrhagic fever virus
  • C. Epstein-barr virus
  • D. Lassa virus
Correct Answer: D

Rationale: The correct answer is D: Lassa virus. The rationale is as follows:
1. Lassa virus belongs to the family Arenaviridae, known for causing Lassa fever.
2. Rabies virus belongs to the Rhabdoviridae family.
3. Crimean-Congo hemorrhagic fever virus belongs to the Nairoviridae family.
4. Epstein-Barr virus belongs to the Herpesviridae family.
In summary, Lassa virus is the correct answer because it is the only virus listed that belongs to the Arenaviridae family.

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.

A wound culture grew Gram-negative rods that were oxidase-positive and lactose non-fermenters. What is the most likely microorganism?

  • A. Pseudomonas aeruginosa
  • B. Escherichia coli
  • C. Salmonella typhi
  • D. Shigella dysenteriae
Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is a Gram-negative rod that is oxidase-positive and lactose non-fermenting. The positive oxidase test indicates the presence of cytochrome c oxidase, a characteristic of P. aerugin. E. coli is lactose fermenting. Salmonella and Shigella are also Gram-negative rods, but they are lactose fermenters, unlike the lactose non-fermenting P. aeruginosa.

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