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Shigella sonnei can escape phagocytic clearance by which mechanism?
- A. Lysis of phagosome and replication in cytoplasm
- B. capsule-mediated inhibition of phagocytosis
- C. Inhibition of phagosome/lysosome fusion
- D. inhibition of opsonization mediated by protein A
Correct Answer: A
Rationale: The correct answer is A because Shigella sonnei escapes phagocytic clearance by lysing the phagosome and replicating in the cytoplasm. This allows the bacterium to avoid being destroyed by the acidic environment and enzymes in the phagolysosome. Choice B is incorrect as Shigella does not have a capsule. Choice C is incorrect because Shigella actually induces phagosome-lysosome fusion to facilitate its escape. Choice D is incorrect as protein A is a component of Staphylococcus aureus, not Shigella sonnei.
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Which bacteria are capable of producing an exotoxin that causes severe diarrhea?
- A. Escherichia coli
- B. Clostridium botulinum
- C. Vibrio cholerae
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all three bacteria listed are capable of producing exotoxins that can cause severe diarrhea. Escherichia coli can produce toxins that lead to diarrhea. Clostridium botulinum produces a neurotoxin causing botulism, which can also result in diarrhea. Vibrio cholerae is known for producing cholera toxin, a potent exotoxin that causes severe watery diarrhea. The other choices are incorrect because each bacterium listed is capable of producing a toxin that can cause diarrhea.
Which bacterium is known for causing food poisoning due to its production of enterotoxins?
- A. Staphylococcus aureus
- B. Clostridium botulinum
- C. Salmonella enterica
- D. Vibrio cholerae
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. This bacterium causes food poisoning by producing enterotoxins that lead to symptoms like nausea and vomiting. Staphylococcus aureus can survive in various food items and multiply rapidly, producing toxins that are heat-stable. Clostridium botulinum causes botulism due to neurotoxins, not enterotoxins. Salmonella enterica causes gastrointestinal infections, not primarily food poisoning. Vibrio cholerae causes cholera by producing a toxin that leads to severe watery diarrhea and dehydration, not enterotoxins like Staphylococcus aureus.
The primary stage of syphilis is usually manifested as:
- A. Diffuse maculopapular rush
- B. Purulent exudation from the urethra
- C. Syphilitic granulomas (gummas)
- D. Non-tender chancre (ulcus durum)
Correct Answer: D
Rationale: The correct answer is D: Non-tender chancre (ulcus durum). In the primary stage of syphilis, an individual typically develops a painless ulcer known as a chancre at the site of infection. This ulcer is usually firm, round, and clean with well-defined borders. It is important to note that it is non-tender, which distinguishes it from other skin conditions. This characteristic helps healthcare providers differentiate syphilis from other sexually transmitted infections.
Explanation for other choices:
A: Diffuse maculopapular rash - This is more commonly associated with secondary syphilis.
B: Purulent exudation from the urethra - This is not a typical presentation of primary syphilis.
C: Syphilitic granulomas (gummas) - Gummas typically develop in the tertiary stage of syphilis, not in the primary stage.
Micellar growth
- A. is observed in bacterial cells
- B. includes a parent and daughter cell which have different sizes
- C. is inherent in viruses and rickettsia
- D. represents apical prolongation of the hyphae in the fungus
Correct Answer: D
Rationale: Step 1: Micellar growth refers to the apical prolongation of hyphae in fungi.
Step 2: Fungi have a unique growth structure with hyphae extending at the tips.
Step 3: This growth pattern allows fungi to expand and access nutrients.
Step 4: Bacterial cells (A) do not exhibit micellar growth.
Step 5: Parent and daughter cells in division have similar sizes, not different (B).
Step 6: Viruses and rickettsia (C) do not display micellar growth.
The first grade pupils were examined in order to sort out children for tuberculosis revaccination. What test was applied for this purpose?
- A. Mantoux test
- B. Schick test
- C. Anthraxine test
- D. Burnet test
Correct Answer: A
Rationale: The correct answer is A: Mantoux test. The Mantoux test is used to detect tuberculosis infection by injecting a small amount of tuberculin under the skin and checking for a reaction. This test helps identify individuals who have been exposed to tuberculosis. The other choices are incorrect because: B: Schick test is used to determine immunity to diphtheria, not tuberculosis. C: Anthraxine test is used for anthrax, not tuberculosis. D: Burnet test is not a recognized medical test for tuberculosis.