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Which of the following bacteria is responsible for causing leprosy?
- A. Mycobacterium leprae
- B. Neisseria gonorrhoeae
- C. Streptococcus pneumoniae
- D. Clostridium perfringens
Correct Answer: A
Rationale: Step 1: Mycobacterium leprae is the bacterium responsible for causing leprosy, a chronic infectious disease affecting the skin and nerves.
Step 2: Neisseria gonorrhoeae causes gonorrhea, a sexually transmitted infection.
Step 3: Streptococcus pneumoniae causes pneumonia and other respiratory infections.
Step 4: Clostridium perfringens causes gas gangrene and food poisoning.
Summary: A is correct as Mycobacterium leprae specifically causes leprosy, while B, C, and D cause different diseases unrelated to leprosy.
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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.
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.
All the statements about Pseudomonas aeruginosa are correct, EXCEPT:
- A. It is a Gram-negative bacterium
- B. It is oxidase-positive
- C. It is non-motile and non-spore forming
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C: It is non-motile and non-spore forming. Pseudomonas aeruginosa is motile due to its flagella and is non-spore forming. A is correct because it is a Gram-negative bacterium, and B is correct as it is oxidase-positive. D is incorrect because C is not true.
In the cytoplasm of some bacteria there are substances in the form of granules. They are:
- A. cytoplasmic inclusions
- B. excess products of the metabolism
- C. reserve substances
- D. all of the above
Correct Answer: D
Rationale: The correct answer is D. Cytoplasmic inclusions in bacteria refer to substances like granules. These granules can be excess products of metabolism or reserve substances stored for future use. Therefore, all of the choices are correct as cytoplasmic inclusions can be any of these substances. A is correct as it directly refers to cytoplasmic inclusions. B is correct as some granules can be excess metabolic products. C is correct as certain granules can serve as reserve substances. Therefore, the correct answer is D, as it encompasses all the possible types of substances found as cytoplasmic inclusions in bacteria.
A laboratory received a food product that had been taken from the focus of food poisoning and presumably contained botulinum toxin. To identify the type of toxin, the neutralization reaction must be performed on white mice. What biological product is used in this reaction?
- A. Antitoxic serum
- B. Normal serum
- C. Antibacterial serum
- D. Diagnosticum
Correct Answer: A
Rationale: The correct answer is A: Antitoxic serum. In the neutralization reaction to identify botulinum toxin, antitoxic serum is used to neutralize the toxin in white mice. Antitoxic serum contains antibodies that specifically target and neutralize the botulinum toxin. Normal serum (B) does not contain the necessary antibodies to neutralize the toxin. Antibacterial serum (C) is not effective against toxins like botulinum. Diagnosticum (D) is a general term and does not specifically refer to the biological product required for this reaction.