Nokea
What type of immunity is responsible for the agglutination of viruses:
- A. Passive immunity
- B. Humoral immunity
- C. Cell mediated immunity
- D. Non specific immunity
Correct Answer: B
Rationale: The correct answer is B: Humoral immunity. Humoral immunity involves the production of antibodies by B cells that can bind to antigens on viruses, leading to their agglutination. This process prevents the spread of the virus in the body. Passive immunity (A) involves receiving pre-formed antibodies, not the production of antibodies. Cell-mediated immunity (C) involves the activation of T cells, not the direct agglutination of viruses. Non-specific immunity (D) refers to general defense mechanisms like inflammation and fever, not targeted agglutination of viruses.
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Endotoxins are released upon:
- A. bacterial replication
- B. cell lysis of gram-negative bacteria
- C. antibody production
- D. formation of spores
Correct Answer: B
Rationale: The correct answer is B because endotoxins are part of the outer membrane of gram-negative bacteria. When these bacteria undergo cell lysis, the endotoxins are released, causing harmful effects. This process does not occur during bacterial replication (choice A), antibody production (choice C), or formation of spores (choice D). Bacterial replication involves the creation of new bacterial cells, not the release of endotoxins. Antibody production is the immune response to pathogens, not the direct cause of endotoxin release. Spores are dormant structures formed by some bacteria, which are not directly related to the release of endotoxins.
A wound culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely microorganism?
- A. Staphylococcus epidermidis
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters indicates a staphylococcal species. The fact that the bacteria are catalase-positive and coagulase-negative further narrow it down to Staphylococcus epidermidis, as this species fits all the given characteristics.
- Choice B, Staphylococcus aureus, is coagulase-positive.
- Choice C, Streptococcus pyogenes, is a streptococcal species, not staphylococcal.
- Choice D, Enterococcus faecalis, is a Gram-positive cocci but is catalase-negative and not typically found in clusters.
What is a common characteristic of spore-forming bacteria?
- A. Resistance to heat and dehydration
- B. Ability to produce toxins
- C. Presence of flagella
- D. Ability to photosynthesize
Correct Answer: A
Rationale: The correct answer is A: Resistance to heat and dehydration. Spore-forming bacteria form spores as a survival mechanism in harsh conditions. These spores are highly resistant to heat and dehydration, allowing the bacteria to withstand extreme environments. This characteristic is essential for their long-term survival and ability to persist in unfavorable conditions. Choices B, C, and D are incorrect because not all spore-forming bacteria produce toxins, have flagella, or are capable of photosynthesis. These characteristics are not exclusive to spore-forming bacteria and do not define them as a group.
Which of the following best describes a Gram-negative bacterium?
- A. Has a thick peptidoglycan layer
- B. Has an outer membrane with lipopolysaccharides
- C. Stains purple
- D. Has no cell wall
Correct Answer: B
Rationale: The correct answer is B because Gram-negative bacteria have an outer membrane with lipopolysaccharides, which is a key characteristic used in Gram staining. This outer membrane is responsible for the pink/red color seen when stained with Gram stain. Choice A is incorrect because Gram-negative bacteria have a thin peptidoglycan layer. Choice C is incorrect because Gram-negative bacteria stain pink, not purple. Choice D is incorrect because all bacteria have a cell wall, but Gram-negative bacteria have a different structure compared to Gram-positive bacteria.
The relations between the macroorganism and the resident skin microflora are defined as:
- A. Commensalism
- B. Infection
- C. Parasitism
- D. No correct answer
Correct Answer: A
Rationale: The correct answer is A: Commensalism. In this relationship, the skin microflora benefits from the host without causing harm or benefitting it. This is evident in the mutualistic interaction where the microflora receive nutrients and a place to live, while the host remains unaffected. Choice B, Infection, is incorrect because it implies harm to the host. Choice C, Parasitism, is also incorrect as it involves one organism benefiting at the expense of the other. Choice D, No correct answer, is not applicable here as Commensalism accurately describes the relationship between the macroorganism and skin microflora.