Nokea
For isolating Rickettsia, the sample is investigated via:
- A. Skin-allergy tests
- B. Serological methods for proving Ab
- C. Chick embryos, cell cultures, and lab animals
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C because Rickettsia requires living cells for growth and replication. Chick embryos, cell cultures, and lab animals provide a suitable environment for Rickettsia isolation. Skin-allergy tests (A) and serological methods for proving antibodies (B) are not directly used for isolating Rickettsia as they do not support the growth of the bacteria. "None of the above" (D) is incorrect as option C involves the appropriate methods for isolating Rickettsia.
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Fungi are free-living _________ organisms:
- A. autotrophic
- B. chemotrophic
- C. heterotrophic
- D. phototrophic
Correct Answer: C
Rationale: The correct answer is C: heterotrophic. Fungi are heterotrophic organisms that obtain nutrients by absorbing organic compounds from their environment. They do not produce their own food through photosynthesis (option A: autotrophic) or chemosynthesis (option B: chemotrophic). Fungi also do not rely on light for energy (option D: phototrophic). Therefore, the correct choice is C as it accurately describes the nutritional mode of fungi.
Which bacteria is responsible for causing the disease known as cholera?
- A. Clostridium botulinum
- B. Vibrio cholerae
- C. Salmonella enterica
- D. Escherichia coli
Correct Answer: B
Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that produces a toxin leading to severe diarrhea and dehydration. Clostridium botulinum (A) causes botulism, Salmonella enterica (C) causes salmonellosis, and Escherichia coli (D) can cause various illnesses but not cholera. Vibrio cholerae is the only bacteria specifically known for causing cholera.
Viruses are characterised by:
- A. They have only one type of nucleic acid
- B. Their extracellular form is referred as “viroidâ€
- C. They are optional intracellular parasites
- D. Their size is measured in micrometers
Correct Answer: A
Rationale: Step 1: Viruses can have either DNA or RNA, not both, hence they have only one type of nucleic acid.
Step 2: The extracellular form of viruses is called virion, not viroid.
Step 3: Viruses are obligate intracellular parasites, meaning they rely on host cells for replication.
Step 4: Viruses are measured in nanometers, not micrometers.
Therefore, the correct answer is A.
A male patient has been diagnosed with gastric ulcer. Bacteriological examination of biopsy material from the affected part of stomach revealed small colonies of gram-negative, oxide reductase-positive flexibacteria that grew on the chocolate agar on the fifth day. Which of the following microorganisms is the most likely causative agent?
- A. Helicobacter pylori
- B. Campilobacter jejuni
- C. Campilobacter fetus
- D. Mycoplasma hominis
Correct Answer: A
Rationale: The correct answer is A: Helicobacter pylori. This bacterium is the most likely causative agent of gastric ulcers. Here's the rationale:
1. Helicobacter pylori is commonly associated with gastric ulcers.
2. It is a gram-negative bacterium that grows on chocolate agar and is oxide reductase-positive.
3. The slow growth on the fifth day is characteristic of H. pylori.
4. Campylobacter jejuni and Campylobacter fetus are not typically associated with gastric ulcers.
5. Mycoplasma hominis is a bacterium that lacks a cell wall and is not commonly found in gastric ulcers.
A 16-year-old adolescent was vaccinated with DTP. In eight days there was stiffness and pain in the joints, subfebrile temperature, urticarial skin eruption, enlargement of inguinal, cervical lymph nodes and spleen. What kind of allergic reaction is observed?
- A. Immunocomplex
- B. Hypersensitivity of immediate type
- C. Cytoxic
- D. Hypersensitivity of delayed type
Correct Answer: D
Rationale: The correct answer is D: Hypersensitivity of delayed type. The symptoms described occur 5-10 days after exposure to the antigen, consistent with a delayed hypersensitivity reaction. This type of reaction involves T cells and is characterized by cell-mediated immune response, leading to inflammation and tissue damage. Choices A, B, and C are incorrect because they are associated with different mechanisms of allergic reactions. Immunocomplex reactions (choice A) involve antigen-antibody complexes depositing in tissues, immediate hypersensitivity reactions (choice B) involve IgE-mediated mast cell degranulation, and cytotoxic reactions (choice C) involve antibodies targeting specific cells for destruction.