Foundations in Microbiology Test Bank

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A patient who came to the doctor because of his infertility was administered to make tests for toxoplasmosis and chronic gonorrhoea. Which reaction should be performed to reveal latent toxoplasmosis and chronic gonorrhoea in this patient?

  • A. RIHA - Reverse indirect hemagglutination assay
  • B. RDHA - Reverse direct hemagglutination assay
  • C. IFA - Immunofluorescence assay
  • D. Immunoblot analysis
Correct Answer: C

Rationale: The correct answer is C: IFA - Immunofluorescence assay. Toxoplasmosis and chronic gonorrhea can be detected using serological tests like IFA. IFA detects specific antibodies in the patient's serum by using fluorescently labeled antibodies. This method is highly sensitive and specific for detecting both acute and latent infections.

Explanation of Incorrect Choices:
A: RIHA - Reverse indirect hemagglutination assay - This test is not commonly used for detecting toxoplasmosis or chronic gonorrhea.
B: RDHA - Reverse direct hemagglutination assay - This test is not typically used for these specific infections.
D: Immunoblot analysis - While Immunoblot analysis is a useful confirmatory test for certain infections, it is not the primary method for detecting toxoplasmosis or chronic gonorrhea.

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The phagocytosis is:

  • A. Killing of bacterial cells with bactericidal antibiotics
  • B. Blocking of key bacterial enzymes
  • C. Active engulf and destruction of microorganisms by some host cells
  • D. There is no correct answer
Correct Answer: C

Rationale: The correct answer is C because phagocytosis refers to the process where certain host cells engulf and destroy microorganisms. This is an essential mechanism of the immune system to eliminate pathogens. Choice A is incorrect because phagocytosis does not involve the use of antibiotics. Choice B is incorrect as it describes a different mechanism of action against bacteria. Choice D is incorrect because phagocytosis is a well-established biological process.

A patient with a long history of chronic gastritis undergoes a gastroscopy, which detects an ulcer in the duodenum area. Microscopic examination of the tissue biopsy developed Gram-negative curved bacteria and the rapid urease activity test of the biopsy material was highly positive. The most likely cause of the disease is:

  • A. Vibrio cholerae
  • B. Campylobacter fetus
  • C. Acinetobacter baumannii
  • D. Helicobacter pylori
Correct Answer: D

Rationale: The correct answer is D: Helicobacter pylori. Helicobacter pylori is a known bacterium associated with causing duodenal ulcers. The presence of Gram-negative curved bacteria in the biopsy along with a highly positive rapid urease test is characteristic of H. pylori infection. Vibrio cholerae causes cholera, not duodenal ulcers. Campylobacter fetus is associated with gastroenteritis, not duodenal ulcers. Acinetobacter baumannii is a nosocomial pathogen, not typically associated with duodenal ulcers. In summary, the unique combination of findings in this case points towards H. pylori as the most likely cause of the disease.

In which of the following GIT infections, the bacteria adhere to the intestine wall and produce toxins

  • A. Shigella spp.
  • B. Salmonella spp.
  • C. enterotoxigenic E. Coli (ETEC)
  • D. Helicobacter pylori
Correct Answer: C

Rationale: The correct answer is C: enterotoxigenic E. Coli (ETEC). ETEC adheres to the intestine wall and produces toxins, leading to symptoms like diarrhea. Shigella spp. invade intestinal cells, Salmonella spp. cause inflammation, and Helicobacter pylori infects the stomach lining. This makes them incorrect choices for bacteria adhering to the intestine wall and producing toxins.

Which of the following organisms produces aflatoxin, a carcinogenic substance?

  • A. Candida albicans
  • B. Claviceps purpurea
  • C. Aspergillus flavus
  • D. Staphylococcus aureus
Correct Answer: C

Rationale: Step-by-step rationale:
1. Aspergillus flavus is a fungus known to produce aflatoxin.
2. Aflatoxin is a potent carcinogen found in contaminated food.
3. Candida albicans is a yeast species not associated with aflatoxin production.
4. Claviceps purpurea is a fungus that produces ergot alkaloids, not aflatoxin.
5. Staphylococcus aureus is a bacterium known for causing food poisoning, not aflatoxin production.

Summary: Aspergillus flavus is the correct answer as it is the organism known to produce aflatoxin, a carcinogenic substance. Other choices are incorrect as they are not associated with aflatoxin production.

A defined microorganism can be isolated in pure culture:

  • A. From liquid and solid media
  • B. From liquid nutrient media
  • C. Only from single colonies on solid media
  • D. None of the above
Correct Answer: C

Rationale: The correct answer is C because isolating a defined microorganism in pure culture involves obtaining a single, distinct colony on solid media. This ensures that only one type of microorganism is present in the culture, preventing contamination. Liquid media can harbor multiple organisms, making it challenging to isolate a specific microorganism. Therefore, choice A is incorrect. Choice B is also incorrect as liquid nutrient media does not provide the necessary isolation required for pure culture. Choice D is incorrect because isolating from single colonies on solid media allows for the pure culture of the defined microorganism.

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