Nokea
Which of the following bacteria is known for causing the disease known as leprosy?
- A. Mycobacterium leprae
- B. Clostridium perfringens
- C. Streptococcus pneumoniae
- D. Neisseria gonorrhoeae
Correct Answer: A
Rationale: Step-by-step rationale:
1. Mycobacterium leprae is the correct answer as it is the bacteria known to cause leprosy.
2. Clostridium perfringens is incorrect as it is associated with gas gangrene.
3. Streptococcus pneumoniae is incorrect as it is commonly linked to pneumonia and meningitis.
4. Neisseria gonorrhoeae is incorrect as it causes gonorrhea, a sexually transmitted infection.
In summary, Mycobacterium leprae is the only bacteria among the choices specifically known to cause leprosy, making it the correct answer.
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A patient with a severe sore throat had a throat culture revealing Gram-positive cocci in chains. The bacteria were beta-hemolytic. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Streptococcus pneumoniae
- C. Enterococcus faecalis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This bacterium is the most likely causative agent due to its characteristic features. Streptococcus pyogenes is Gram-positive cocci in chains, which matches the description provided in the question. It is also known to be beta-hemolytic, causing complete lysis of red blood cells on blood agar. Streptococcus pyogenes is a common pathogen causing sore throat, often associated with pharyngitis.
Explanation for incorrect choices:
B: Streptococcus pneumoniae - This bacterium is Gram-positive but usually occurs in pairs (diplococci) and is alpha-hemolytic.
C: Enterococcus faecalis - This bacterium is Gram-positive cocci but is not typically beta-hemolytic and is not commonly associated with sore throat infections.
D: Staphylococcus aureus - This bacterium is Gram-positive cocci but usually occurs in clusters and
The type of antibody that can cross the placenta is:
- A. IgA
- B. IgM
- C. IgG
- D. IgD
Correct Answer: C
Rationale: The correct answer is C: IgG. IgG is the only antibody that can cross the placenta due to its small size and unique structure, allowing it to provide passive immunity to the fetus. IgA is mainly found in mucosal secretions, IgM is too large to cross the placental barrier, and IgD plays a role in B cell activation but is not involved in placental transfer.
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.
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.
Non - complete phagocytosis is observed during infections with:
- A. Mycobacterium tuberculosis
- B. Legionella pneumophila
- C. Brucella melitensis
- D. A + B + C
Correct Answer: D
Rationale: Rationale:
1. Mycobacterium tuberculosis, Legionella pneumophila, Brucella melitensis can evade complete phagocytosis.
2. Mycobacterium tuberculosis inhibits phagosome-lysosome fusion.
3. Legionella pneumophila can prevent phagosome maturation.
4. Brucella melitensis can survive and replicate within phagocytes.
5. A + B + C together represent non-complete phagocytosis.
Summary:
- A, B, C individually cause incomplete phagocytosis.
- Only when all three are present together (D) is non-complete phagocytosis observed.