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A 45-year-old patient has foul-smelling diarrhea. Stool examination revealed large ciliated protozoa with a kidney-shaped macronucleus. What is the causative agent?
- A. Balantidium coli
- B. Entamoeba histolytica
- C. Giardia lamblia
- D. Trichomonas hominis
Correct Answer: A
Rationale: The correct answer is A: Balantidium coli. This large ciliated protozoa with a kidney-shaped macronucleus is characteristic of Balantidium coli, an intestinal parasite known to cause foul-smelling diarrhea in humans. Balantidium coli is the only option among the choices that fits this specific description. Entamoeba histolytica causes amoebic dysentery, Giardia lamblia causes giardiasis, and Trichomonas hominis is a non-pathogenic protozoa found in the intestinal tract. Therefore, based on the morphology described in the question, Balantidium coli is the correct causative agent.
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Which of the following infectious disease is considered a newly emerging disease?
- A. Hantavirus
- B. Malaria
- C. Tuberculosis
- D. Chlamydia
Correct Answer: A
Rationale: The correct answer is A: Hantavirus. Hantavirus is considered a newly emerging disease because it was first identified in the late 20th century. It is transmitted to humans through rodents and can lead to severe respiratory illness. Malaria, Tuberculosis, and Chlamydia are not considered newly emerging diseases as they have been known for centuries and continue to be prevalent worldwide. Therefore, based on the timeline of discovery and emergence, Hantavirus is the most recent infectious disease among the options provided.
Cell mediated immunity has a leading role in:
- A. Infections with facultative and obligate intracellular pathogens
- B. Infections with extracellular pathogens
- C. Type 1 hypersensitivity reactions
- D. Toxin mediated infections
Correct Answer: A
Rationale: Cell-mediated immunity plays a crucial role in combating infections with intracellular pathogens by activating T cells to directly kill infected cells. Facultative and obligate intracellular pathogens, such as viruses and some bacteria, require cell-mediated immunity for effective clearance. Option A is correct due to the specificity of this immune response. Choices B, C, and D are incorrect as they are primarily associated with humoral immunity involving antibodies and not T cell responses against intracellular pathogens.
Which scientist is most responsible for ending the controversy about spontaneous generation?
- A. John Needham
- B. Joseph Lister
- C. Louis Pasteur
- D. Robert Koch
Correct Answer: C
Rationale: The correct answer is C: Louis Pasteur. He conducted experiments that definitively disproved the theory of spontaneous generation through his famous swan-neck flask experiment. By showing that microorganisms only appeared in the broth when exposed to air, Pasteur demonstrated that they did not arise spontaneously. John Needham's experiments were inconclusive, Joseph Lister is known for his contributions to antiseptic surgery, and Robert Koch is credited with developing Koch's postulates for identifying the causative agents of diseases, but neither of them directly contributed to ending the controversy about spontaneous generation.
Which of these viruses is a laboratory product?
- A. Monkeypox
- B. Variola
- C. Vaccinia
- D. Cowpox
Correct Answer: C
Rationale: Rationale:
1. Vaccinia is a laboratory product used in smallpox vaccination.
2. Variola is the virus that causes smallpox, not a laboratory product.
3. Monkeypox is a naturally occurring virus, not a laboratory product.
4. Cowpox can be found in nature and is used in vaccine production, but it is not a laboratory product like Vaccinia.
Mesophylic bacteria are with temperature optimum:
- A. 25-37 °C
- B. 55-65 °C
- C. 15-18 °C
- D. 38-45 °C
Correct Answer: A
Rationale: The correct answer is A (25-37 °C) because mesophilic bacteria thrive best at moderate temperatures typical of most environments, making 25-37 °C their optimum range. This range allows for optimal enzyme activity and growth. Choice B (55-65 °C) is incorrect as it is more suitable for thermophilic bacteria. Choice C (15-18 °C) is too low for mesophiles to thrive efficiently. Choice D (38-45 °C) is too high and is more suitable for thermophiles. Ultimately, the correct answer aligns with the typical temperature range where mesophilic bacteria are most active and abundant.