Nokea
Which of the following bacteria produces a toxin that inhibits protein synthesis?
- A. Shigella dysenteriae
- B. Escherichia coli
- C. Clostridium tetani
- D. Staphylococcus aureus
Correct Answer: A
Rationale: Rationale: Shigella dysenteriae produces Shiga toxin, which inhibits protein synthesis by inactivating the 60S ribosomal subunit. This disrupts the translation process, leading to cell death. Escherichia coli (choice B) does not produce a toxin that inhibits protein synthesis. Clostridium tetani (choice C) produces tetanospasmin, which affects the nervous system. Staphylococcus aureus (choice D) produces toxins that cause food poisoning but do not inhibit protein synthesis.
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Which of the following viruses belong to family Arenaviridae
- A. Lassa virus
- B. Crimean-Congo hemorrhagic fever virus
- C. Rabies virus
- D. Epstein-Bar virus
Correct Answer: A
Rationale: The correct answer is A: Lassa virus. The rationale is as follows:
1. Lassa virus is a member of the Arenaviridae family, known for causing Lassa fever.
2. Arenaviridae family includes viruses with a segmented genome and are transmitted through rodents.
3. Crimean-Congo hemorrhagic fever virus (Choice B) belongs to the Bunyaviridae family, not Arenaviridae.
4. Rabies virus (Choice C) belongs to the Rhabdoviridae family, not Arenaviridae.
5. Epstein-Barr virus (Choice D) belongs to the Herpesviridae family, not Arenaviridae.
In summary, Lassa virus is the correct choice as it aligns with the characteristics of the Arenaviridae family, while the other choices belong to different virus families.
Which of the following bacteria is responsible for causing the disease tetanus?
- A. Clostridium tetani
- B. Clostridium perfringens
- C. Streptococcus pyogenes
- D. Escherichia coli
Correct Answer: A
Rationale: The correct answer is A: Clostridium tetani. This bacterium is responsible for causing tetanus due to its production of tetanus toxin. Clostridium perfringens (B) causes gas gangrene, Streptococcus pyogenes (C) causes strep throat and skin infections, and Escherichia coli (D) is a common gut bacteria that can cause food poisoning but not tetanus.
A patient with a sore throat and fever had a throat culture revealing Gram-positive cocci in pairs with a capsule. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Neisseria meningitidis
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is a Gram-positive cocci that often appear in pairs and can have a capsule. It is a common cause of sore throat and fever, known as streptococcal pharyngitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form pairs. Neisseria meningitidis (C) is a Gram-negative diplococcus and is more associated with meningitis. Klebsiella pneumoniae (D) is a Gram-negative rod and not typically associated with sore throat and fever.
Microscopy of dental plaque revealed unicellular organisms. Their cytoplasm had two distinct layers, barely visible core, wide pseudopodia. The patient is most likely to have:
- A. Entamoeba gingivalis
- B. Entamoeba histolytica
- C. Lamblia
- D. Trichomonas tenax
Correct Answer: D
Rationale: The correct answer is D: Trichomonas tenax. Trichomonas tenax is a flagellated protozoan that is commonly found in the oral cavity, specifically in dental plaque. The description provided in the question matches the characteristics of Trichomonas tenax, such as unicellular structure, distinct layers in the cytoplasm, wide pseudopodia, and barely visible core. Entamoeba gingivalis (choice A) and Entamoeba histolytica (choice B) are amoebas, not flagellated protozoa, and they do not exhibit the characteristics described in the question. Lamblia (choice C) is also an incorrect choice as it is a different type of protozoan that does not match the description provided.
Which of the following bacteria can cause meningitis?
- A. Neisseria meningitidis
- B. Haemophilus influenzae
- C. Streptococcus pneumoniae
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D, "All of the above." Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae are all bacteria known to cause meningitis. Neisseria meningitidis is a common cause of bacterial meningitis in young adults, Haemophilus influenzae type b is a common cause in children, and Streptococcus pneumoniae is a leading cause in adults and the elderly. Therefore, all three bacteria can potentially cause meningitis depending on the age group and other factors. The other choices are incorrect because each of the bacteria listed can cause meningitis, so selecting only one of them would be incorrect.