Nokea
Which of the following bacterial structures has endotoxic activity?
- A. Lipopolysaccharides
- B. Lipoproteins of Braun
- C. Protein A
- D. None
Correct Answer: A
Rationale: The correct answer is A: Lipopolysaccharides. Lipopolysaccharides (LPS) are major components of the outer membrane of Gram-negative bacteria and are known to have endotoxic activity. LPS can trigger a strong immune response leading to inflammation and septic shock.
Choice B, Lipoproteins of Braun, are not known to have endotoxic activity. Choice C, Protein A, is a surface protein found in Staphylococcus aureus and is not associated with endotoxic activity. Choice D, None, is incorrect as LPS is indeed a bacterial structure with endotoxic activity.
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Which of the following food media can be used for cultivation of Streptococcus pneumoniae:
- A. Blood agar
- B. MacConkey agar
- C. Peptone water
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Blood agar. Streptococcus pneumoniae is a fastidious bacterium that requires enriched media for growth. Blood agar provides the necessary nutrients and growth factors for the cultivation of S. pneumoniae, such as blood proteins and hemin. MacConkey agar (B) is selective for gram-negative bacteria and would not support the growth of S. pneumoniae. Peptone water (C) is a liquid medium that lacks the necessary nutrients for the growth of S. pneumoniae. Choice D is incorrect as blood agar is a suitable medium for cultivating S. pneumoniae.
A patient with severe abdominal pain and diarrhea had a stool sample cultured. The bacteria were Gram-negative rods that did not ferment lactose. What is the most likely causative agent?
- A. Salmonella enterica
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: A
Rationale: The correct answer is A: Salmonella enterica. This is because Salmonella are Gram-negative rods that do not ferment lactose, which fits the description in the question. Additionally, Salmonella is a common cause of severe abdominal pain and diarrhea. Shigella dysenteriae is a Gram-negative rod that also causes severe diarrhea but it does not share the characteristic of not fermenting lactose. Escherichia coli is a Gram-negative rod that does ferment lactose. Proteus vulgaris is also a Gram-negative rod but it is not commonly associated with severe abdominal pain and diarrhea, making it an unlikely causative agent in this scenario.
The role of pili in bacteria is:
- A. protection from desiccation
- B. motility
- C. adhesion to surfaces and conjugation
- D. spore formation
Correct Answer: C
Rationale: The correct answer is C: adhesion to surfaces and conjugation. Pili are hair-like structures on the surface of bacteria that help them adhere to surfaces and facilitate the transfer of genetic material during conjugation. This is essential for bacterial survival and reproduction. Choice A is incorrect because protection from desiccation is typically associated with other structures like capsules. Choice B is incorrect as motility in bacteria is usually facilitated by flagella. Choice D is incorrect as spore formation involves the formation of specialized structures, not pili.
Respiratory tract infections can be caused by:
- A. Francisella tularensis
- B. Bordetella pertussis
- C. Coxiella brunetti
- D. All are correct
Correct Answer: D
Rationale: The correct answer is D because all the options listed can cause respiratory tract infections.
1. Francisella tularensis can cause pneumonia.
2. Bordetella pertussis causes whooping cough, a respiratory infection.
3. Coxiella brunetti can lead to Q fever, which affects the respiratory system.
Therefore, all choices are correct for causing respiratory tract infections. Choices A, B, and C are incorrect because they are individual causes of respiratory infections, whereas choice D encompasses all possible causes listed.
The antigen receptors on the surface of B-lymphocytes are made by proteins:
- A. TRUE
- B. FALSE
- C. Both answers can be correct depending on the given situation
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: TRUE. B-lymphocyte antigen receptors are made by proteins called immunoglobulins. These proteins are essential for recognizing and binding to specific antigens. They play a crucial role in the immune response. Choice B is incorrect because B-lymphocyte antigen receptors are indeed made by proteins. Choice C is incorrect as well because in this case, the correct answer is that the receptors are made by proteins. Choice D is also incorrect as the receptors are made by proteins.