Correct Answer: A

Rationale: The correct answer is A: Metronidazole. Amebic dysentery is caused by the parasite Entamoeba histolytica, not bacteria. Metronidazole is the drug of choice for treating this parasitic infection. It works by disrupting the DNA structure of the parasite, leading to its death. Mebendazole (B) is used to treat certain worm infections, not amebic dysentery. Itrakonazole (C) is an antifungal medication and not effective against parasites. Furacillin (D) is an antibacterial agent and not suitable for treating parasitic infections like amebic dysentery.

Correct Answer: B

Rationale: The correct answer is B: Hantavirus. Hantaviruses are not arthropod-borne, unlike the other choices. Hantaviruses are transmitted to humans primarily through contact with rodent urine, feces, or saliva. Phlebovirus (A), Nairovirus (C), and Uukuvirus (D) are all bunyaviruses that are transmitted by arthropod vectors such as mosquitoes or ticks. Therefore, Hantavirus is the correct answer as it is not transmitted by arthropods.

Correct Answer: C

Rationale: The correct answer is C: Staphylococcus saprophyticus. The rationale is that Staphylococcus saprophyticus is the only one among the listed species that is known to be resistant to novobiocin. This resistance is due to the specific mechanism of action of novobiocin, which targets DNA gyrase, and Staphylococcus saprophyticus possesses an altered DNA gyrase enzyme that renders it resistant to the antibiotic. Staphylococcus aureus and Staphylococcus epidermidis are susceptible to novobiocin, making choices A and B incorrect. Choice D, "none of the listed," is also incorrect as Staphylococcus saprophyticus is indeed resistant to novobiocin.

Correct Answer: A

Rationale: The correct answer is A: Cell wall rigidity. Teichoic acid in Gram-positive bacteria helps to maintain the structural integrity of the cell wall by providing rigidity and stability. It also plays a role in regulating the movement of ions across the cell membrane. Choices B, C, and D are incorrect because teichoic acid is not involved in energy production, spore formation, or motility in bacteria. It primarily functions in cell wall maintenance and integrity.

Correct Answer: C

Rationale: The correct answer is C: Bacillus, Clostridium. Both Bacillus and Clostridium are known to form spores. Bacillus species produce endospores, which are resistant structures for survival in harsh conditions, while Clostridium species also form spores for protection and dispersal. The other choices are incorrect because Borrelia and Treponema are spirochetes and do not form spores, Bacteroides and Fusobacterium are anaerobic bacteria that do not produce spores, and Bordetella and Brucella are non-spore forming bacteria as well.