Nokea
Which of the following(s) is/are the determinants of antigenicity?
- A. Chemical nature
- B. Size of the antigen
- C. Foreign origin
- D. All of these
Correct Answer: D
Rationale: The correct answer is D, as all options A, B, and C are determinants of antigenicity.
A: Chemical nature influences how the immune system recognizes antigens.
B: The size of the antigen affects its ability to be recognized by immune cells.
C: Antigens of foreign origin are more likely to trigger an immune response.
Therefore, all of these factors together play a crucial role in determining antigenicity.
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Which one is FALSE:
- A. Tissue samples and aspirations are better specimens than the swabs for diagnosis of skin and soft tissue infections
- B. To prove anaerobic agents. The specimen should be collected from the surface of the wound.
- C. The skin rash in some infections is due to the excessive production
- D. Healthy skin is an impenetrable barrier for the microorganisms
Correct Answer: B
Rationale: The correct answer is B because collecting specimens from the surface of a wound does not provide adequate samples for anaerobic agent detection. Anaerobic agents thrive in deep tissue environments with low oxygen levels, making surface specimens unreliable. Tissue samples and aspirations (choice A) are superior for diagnosing skin infections. Excessive production of toxins, not skin rash (choice C), causes symptoms in some infections. While healthy skin provides some protection, it is not completely impenetrable to microorganisms (choice D).
Lipopolysaccharides (LPS) are found in:
- A. Gram-positive bacteria
- B. Fungal cell walls
- C. Gram-negative bacterial outer membrane
- D. Viral capsids
Correct Answer: C
Rationale: The correct answer is C: Gram-negative bacterial outer membrane. Lipopolysaccharides (LPS) are major components of the outer membrane of Gram-negative bacteria. LPS consist of lipid A, core oligosaccharide, and O-antigen. They play a crucial role in the structural integrity and protection of Gram-negative bacteria.
Choice A (Gram-positive bacteria) is incorrect because LPS are not present in Gram-positive bacteria. Choice B (Fungal cell walls) is incorrect as LPS are specific to bacterial outer membranes. Choice D (Viral capsids) is incorrect as LPS are not associated with viral structures.
Koch apparatus uses temperature of:
- A. 90°C
- B. 95°C
- C. 100°C
- D. 110°C
Correct Answer: C
Rationale: The correct answer is C (100°C) because the Koch apparatus is used for sterilization, and the standard temperature for sterilization is 100°C. At this temperature, most microorganisms are killed, making it an effective method for sterilization. Choice A (90°C), B (95°C), and D (110°C) are incorrect because they are not commonly used temperatures for sterilization purposes. Choosing a temperature lower than 100°C may not effectively kill all microorganisms, while choosing a temperature higher than 100°C may lead to unnecessary energy consumption without providing additional sterilization benefits.
Which bacteria are known for their ability to survive in extreme heat?
- A. Psychrophiles
- B. Mesophiles
- C. Thermophiles
- D. Halophiles
Correct Answer: C
Rationale: The correct answer is C: Thermophiles. Thermophiles are bacteria that thrive in high temperatures typically above 45°C. They have specialized enzymes and cellular structures that allow them to survive and even thrive in extreme heat. Psychrophiles (A) are adapted to cold temperatures, mesophiles (B) thrive at moderate temperatures, and halophiles (D) prefer high salt concentrations, making them unsuitable for extreme heat survival. Therefore, Thermophiles are the only bacteria among the choices that are known for their ability to survive in extreme heat.
Which of the following is the causative agent of tetanus?
- A. Clostridium botulinum
- B. Clostridium tetani
- C. Bacillus anthracis
- D. Staphylococcus aureus
Correct Answer: B
Rationale: The correct answer is B: Clostridium tetani. This bacterium produces tetanospasmin toxin, causing tetanus. Clostridium botulinum (choice A) produces botulinum toxin, leading to botulism. Bacillus anthracis (choice C) causes anthrax, not tetanus. Staphylococcus aureus (choice D) can cause various infections, but not tetanus. Therefore, only Clostridium tetani is the causative agent of tetanus.