Nokea
Which of the following viral infections can result in chronic carrier state.
- A. HBV
- B. HCV
- C. HDV
- D. All of these
Correct Answer: D
Rationale: The correct answer is D: All of these. HBV, HCV, and HDV can all lead to chronic carrier states due to their ability to establish persistent infections in the liver. HBV can result in chronic hepatitis, cirrhosis, and even liver cancer. HCV can also lead to chronic hepatitis and liver damage. HDV is a defective virus that requires HBV for replication and can worsen the outcome of HBV infection, potentially leading to chronic liver disease. Therefore, all three viruses have the potential to cause chronic carrier states.
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A child with diarrhea had stool microscopy revealing cysts with four nuclei. What is the most likely causative agent?
- A. Entamoeba histolytica
- B. Giardia lamblia
- C. Balantidium coli
- D. Trichomonas hominis
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This pathogen is known to cause amoebic dysentery, characterized by diarrhea with bloody or mucoid stools. The presence of cysts with four nuclei in the stool microscopy is a characteristic feature of Entamoeba histolytica. Other choices are incorrect because Giardia lamblia typically presents with binucleate cysts, Balantidium coli is a ciliated protozoan, and Trichomonas hominis is a non-pathogenic parasite found in the human intestine.
Viruses cannot multiply in:
- A. Artificial nutrient media
- B. Living cells
- C. Human embryonic cells
- D. Bacteria
Correct Answer: A
Rationale: The correct answer is A: Artificial nutrient media. Viruses are obligate intracellular parasites, meaning they require living host cells to replicate. They cannot multiply in artificial nutrient media as they lack the cellular machinery necessary for viral replication. Living cells, including human embryonic cells and bacteria, provide the required cellular environment for viruses to replicate. Therefore, options B, C, and D are incorrect as they all contain living cells that can support viral multiplication.
Which of the following media is used to isolate Neisseria gonorrhoeae?
- A. Phenylethyl alcohol agar
- B. Thayer-Martin agar
- C. MacConkey agar
- D. Mannitol salt agar
Correct Answer: B
Rationale: The correct answer is B: Thayer-Martin agar. This selective media contains antibiotics that inhibit the growth of other organisms while allowing Neisseria gonorrhoeae to grow. The antibiotics in Thayer-Martin agar include vancomycin, colistin, nystatin, and trimethoprim, which target different types of bacteria, ensuring the isolation of N. gonorrhoeae. Phenylethyl alcohol agar (A) is used to isolate gram-positive organisms, not N. gonorrhoeae. MacConkey agar (C) is selective for gram-negative enteric bacteria. Mannitol salt agar (D) is used for isolating Staphylococcus species based on their ability to ferment mannitol.
Which of the following bacteria is associated with food poisoning caused by improperly canned foods?
- A. Clostridium botulinum
- B. Escherichia coli
- C. Salmonella enterica
- D. Vibrio cholerae
Correct Answer: A
Rationale: The correct answer is A: Clostridium botulinum. This bacterium is associated with food poisoning from improperly canned foods due to its ability to produce botulinum toxin, a potent neurotoxin that causes botulism. Improper canning allows spores of Clostridium botulinum to survive and germinate, producing the toxin in anaerobic conditions. The other choices are incorrect because Escherichia coli, Salmonella enterica, and Vibrio cholerae are not typically associated with food poisoning from improperly canned foods. Escherichia coli and Salmonella are more commonly linked to contaminated water or undercooked food, while Vibrio cholerae causes cholera primarily through contaminated water sources.
Enriched growth media:
- A. Belong to the minimal media and inhibit the development of gram+ cocci
- B. Support the development of the target bacteria groups without suppressing the growth of other microorganisms
- C. Are intended for the cultivation of only one microbial species
- D. Support the development of target bacteria groups and suppress the development of other microorganisms
Correct Answer: B
Rationale: The correct answer is B because enriched growth media provide essential nutrients that support the growth of target bacteria groups without inhibiting the growth of other microorganisms. This allows for the selective cultivation of specific microbes while still allowing for the growth of other organisms present in the sample. Choice A is incorrect because enriched media do not belong to minimal media and do not inhibit the development of gram+ cocci. Choice C is incorrect because enriched media can support the growth of multiple microbial species. Choice D is incorrect because enriched media do not suppress the development of other microorganisms but rather provide nutrients to support their growth alongside the target bacteria groups.