Which of the following bacteria is responsible for causing the disease diphtheria?

Correct Answer: B

Rationale: The correct answer is B: Corynebacterium diphtheriae. This bacterium produces a toxin that causes diphtheria. It forms a grayish membrane in the throat, leading to difficulty breathing. Bacillus anthracis (Choice A) causes anthrax, Streptococcus pneumoniae (Choice C) causes pneumonia, and Escherichia coli (Choice D) causes various infections but not diphtheria.

Correct Answer: A

Rationale: The correct answer is A: Shigella dysenteriae. This bacterium produces Shiga toxin, which inhibits protein synthesis by inactivating the ribosomes. Shigella dysenteriae is known to cause severe gastrointestinal infections. Choice B: Escherichia coli typically does not produce toxins that inhibit protein synthesis. E. coli strains may produce toxins that cause diarrhea. Choice C: Clostridium tetani produces tetanospasmin toxin, which affects the nervous system but does not inhibit protein synthesis. Choice D: Staphylococcus aureus produces toxins like enterotoxins and exotoxins but these toxins do not directly inhibit protein synthesis.

Correct Answer: A

Rationale: The correct answer is A: Vibrio cholerae. This bacterium is commonly associated with foodborne illnesses caused by contaminated water due to its ability to survive and multiply in water sources. Vibrio cholerae causes cholera, a severe gastrointestinal infection transmitted through contaminated food and water. Clostridium difficile, Mycobacterium tuberculosis, and Neisseria gonorrhoeae are not typically associated with foodborne illnesses caused by contaminated water. Clostridium difficile causes gastrointestinal infections linked to antibiotic use, Mycobacterium tuberculosis causes tuberculosis through respiratory transmission, and Neisseria gonorrhoeae causes sexually transmitted infections.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. Clostridium botulinum produces the neurotoxin that causes botulism. This bacterium thrives in anaerobic conditions and contaminated food. The neurotoxin blocks acetylcholine release at the neuromuscular junction, leading to muscle paralysis. Choices B, C, and D are incorrect because Clostridium tetani causes tetanus, Escherichia coli can cause food poisoning but not botulism, and Staphylococcus aureus produces enterotoxins causing food poisoning, not botulism.

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the neurotoxin responsible for botulism. Clostridium perfringens is associated with gas gangrene, not botulism. Streptococcus pneumoniae causes pneumonia, and Neisseria gonorrhoeae causes gonorrhea, not botulism. Therefore, A is the correct choice.