Spores are destroyed by:

Correct Answer: A

Rationale: The correct answer is A because spores are heat-resistant and require high temperatures for destruction. Autoclaving at 121°C for 15-20 minutes ensures spore destruction due to the high pressure and temperature. Choice B (heating to 80°C) is insufficient to destroy spores. Choice C (boiling at 100°C for 10 minutes) is also inadequate as spores require higher temperatures for elimination. Choice D (None of them) is incorrect as autoclaving is the standard method for spore sterilization.

Correct Answer: A

Rationale: The correct answer is A because spores are heat-resistant and require high temperatures for destruction. Autoclaving at 121°C for 15-20 minutes ensures spore destruction due to the high pressure and temperature. Choice B (heating to 80°C) is insufficient to destroy spores. Choice C (boiling at 100°C for 10 minutes) is also inadequate as spores require higher temperatures for elimination. Choice D (None of them) is incorrect as autoclaving is the standard method for spore sterilization.

Correct Answer: D

Rationale: The correct answer is D because virulent strains of Listeria monocytogenes exhibit multiple pathogenic factors. A: They do not have endotoxin-like substances, so this is incorrect. B: They are indeed facultative intracellular bacteria, aiding in their ability to survive and replicate inside host cells. C: They produce hemolysin, which helps them lyse red blood cells. Therefore, the correct answer is D, as all of the above statements are true for virulent strains of Listeria monocytogenes.

Correct Answer: A

Rationale: The correct answer is A: Salk and Sabin vaccines are vaccines against polio. Both Salk and Sabin vaccines are indeed vaccines specifically developed to prevent polio. The Salk vaccine is an inactivated polio vaccine, while the Sabin vaccine is an oral live attenuated vaccine. Therefore, choice B is incorrect as the Sabin vaccine is live attenuated, not inactivated. Choice C is also incorrect because the Salk vaccine is inactivated, not live attenuated. Choice D is incorrect because not all statements are true; only statement A is accurate.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Fimbriae are hair-like structures on bacteria, not rope-like. 2. Fimbriae are smaller in diameter compared to flagella. 3. Fimbriae are used for adherence or conjugation, not flagella. Therefore, choice B is correct as it incorrectly describes fimbriae, while choices A, C, and D correctly characterize fimbriae.