Which bacteria are responsible for causing the plague?

Correct Answer: B

Rationale: The correct answer is B: Yersinia pestis. Yersinia pestis is the bacterium responsible for causing the plague, specifically the bubonic plague. It is transmitted through fleas and rodents. Escherichia coli (A) is a common gut bacterium, Clostridium difficile (C) causes antibiotic-associated diarrhea, and Staphylococcus aureus (D) is associated with skin infections, but they are not responsible for causing the plague.

Correct Answer: B

Rationale: The correct answer is B: Neisseria meningitidis. This is because Neisseria meningitidis is a Gram-negative diplococci that is oxidase-positive and fermentative. Neisseria gonorrhoeae (choice A) is also a Gram-negative diplococci but is not fermentative. Haemophilus influenzae (choice C) is not a diplococci and Moraxella catarrhalis (choice D) is oxidase-negative. Thus, Neisseria meningitidis fits all the criteria provided in the question, making it the most likely causative agent for the sepsis in this patient.

Correct Answer: C

Rationale: The correct answer is C: prions. Prions are misfolded proteins that can cause transmissible spongiform encephalopathies like Creutzfeldt-Jakob disease. Prions are not viruses like flavoviruses (A) or orthomyxoviruses (D). Virusoids (B) are small, circular, single-stranded RNA molecules that require a helper virus to replicate and are not associated with transmissible spongiform encephalopathies. Therefore, the correct answer is C as prions are the only choice that correctly links to the etiology of transmissible spongiform encephalopathies.

Correct Answer: D

Rationale: The correct answer is D (All of the above) because all three bacteria listed produce exotoxins that cause severe gastrointestinal illness. Clostridium botulinum produces botulinum toxin causing botulism. Vibrio cholerae produces cholera toxin leading to cholera. Escherichia coli can produce various exotoxins causing different types of severe gastrointestinal illnesses like E. coli O157:H7 causing bloody diarrhea. Therefore, all choices A, B, and C are correct in this case as they all produce exotoxins causing severe gastrointestinal illness.

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that infects the small intestine, leading to severe diarrhea and dehydration. This bacterium produces a toxin that causes the symptoms of cholera. A: Shigella dysenteriae causes dysentery, not cholera. C: Salmonella enterica causes food poisoning, not cholera. D: Escherichia coli can cause food poisoning but not cholera.

Correct Answer: B

Rationale: The correct answer is B: protein filaments made of flagellin. Bacterial flagella are composed of flagellin proteins arranged in helical filaments. This structure allows for movement and propulsion of bacteria. A: 9+2 microtubule arrangement is incorrect because this structure is typically found in eukaryotic flagella, not bacterial flagella. C: Lipid bilayer is incorrect as it is a structural component of cell membranes, not bacterial flagella. D: Peptidoglycan layer is incorrect as it is a component of bacterial cell walls, not flagella.

Correct Answer: B

Rationale: The correct answer is B: Shigella. On Endo agar, Shigella appears as colorless colonies due to its inability to ferment lactose. Shigella is a Gram-negative rod and is a common cause of diarrhea. Salmonella (A) and Escherichia coli (C) would typically produce pink colonies on Endo agar as they can ferment lactose. Proteus (D) is not commonly associated with diarrhea and would not be expected to grow on Endo agar.

Correct Answer: B

Rationale: The correct answer is B: Simpler. Prokaryotic cytoplasm is simpler than eukaryotic cytoplasm because prokaryotic cells lack membrane-bound organelles such as a nucleus, mitochondria, and endoplasmic reticulum that are present in eukaryotic cells. Prokaryotic cytoplasm contains fewer components and structures compared to eukaryotic cytoplasm, making it less complex. Therefore, the prokaryotic cytoplasm is simpler in structure. Choices A, C, and D are incorrect because prokaryotic cytoplasm is not more complex than eukaryotic cytoplasm, there is a clear difference in structure between prokaryotic and eukaryotic cytoplasm, and the statement "None of the above" is not accurate as the correct answer is B.

Correct Answer: B

Rationale: The correct answer is B: Syphilis. The Wasserman reaction is a test for syphilis, specifically for detecting antibodies against the bacterium Treponema pallidum. In a 30-year-old man with a markedly positive Wasserman reaction, it indicates an active syphilis infection. Brucellosis (Choice A) is not diagnosed using the Wasserman reaction. Poliomyelitis (Choice C) is a viral infection affecting the spinal cord, not diagnosed using the Wasserman reaction. Influenza (Choice D) is a respiratory viral infection, not associated with the Wasserman reaction.