Not many bacterial species in nature form spores. Which of the following genera have this ability?

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.

Correct Answer: B

Rationale: The correct answer is B: Bacillus subtilis. Bacillus subtilis is a Gram-positive bacterium known for forming endospores, which are resistant structures that allow the bacteria to survive harsh conditions like heat, radiation, and desiccation. This ability to form spores helps Bacillus subtilis to endure unfavorable environments. Staphylococcus aureus (A), Pseudomonas aeruginosa (C), and Neisseria gonorrhoeae (D) do not form spores and lack the same level of resistance to extreme conditions as Bacillus subtilis.

Correct Answer: B

Rationale: The correct answer is B: Family Reoviridae. Reassortment of gene segments occurs in segmented viruses like Reoviruses. In Reoviridae, each segment encodes a specific protein, allowing for reassortment to generate new strains. Togaviridae (A) is a non-segmented virus, not capable of reassortment. Picornaviridae (C) and Paramyxoviruses (D) are also non-segmented viruses, limiting their ability for reassortment. Therefore, the correct choice is B due to the segmented nature of Reoviruses allowing for genetic reassortment.

Correct Answer: A

Rationale: The correct answer is A: 1 chromosome. Bacterial cells typically have a singular circular chromosome that contains their genetic material. This chromosome is essential for the cell's survival and contains all the necessary genetic information for its functions. Choices B, C, and D are incorrect because they refer to the chromosome numbers found in human cells (23 pairs or 46 individual chromosomes). Bacteria, being prokaryotic organisms, have a simpler genetic makeup compared to eukaryotic organisms like humans, hence they possess only one chromosome.

Correct Answer: A

Rationale: The correct answer is A: Wright's agglutination reaction. For brucellosis diagnosis, this test detects antibodies against Brucella species. Wright's test specifically targets agglutinins, which are produced in response to Brucella infection. The other choices are incorrect because: B: Widal's test is used for typhoid fever caused by Salmonella typhi. C: Ascoli's test is for pneumococcal infections. D: Weigl's test is used for typhus fever caused by Rickettsia prowazekii.

Correct Answer: A

Rationale: The correct answer is A: Tuberculine. The Mantoux test involves injecting tuberculin, a protein derivative of Mycobacterium tuberculosis, under the skin. This test helps determine if a person has been exposed to the bacteria that cause TB. Administering tuberculin is crucial for the Mantoux test as it triggers a delayed-type hypersensitivity reaction in individuals previously exposed to TB. Choice B (BCG vaccine) is incorrect because BCG does not interfere with the Mantoux test results. Choice C (DPT vaccine) is incorrect as it is used for immunization against diphtheria, pertussis, and tetanus, not for diagnosing TB. Choice D (Tularin test) is incorrect as it is not a recognized immunobiological agent for TB diagnosis.

Correct Answer: A

Rationale: The correct answer is A: Listeria monocytogenes. This pathogen can cross the placenta and infect the fetus, leading to serious complications. Listeria can cause miscarriage, stillbirth, or severe neonatal infections. Staphylococcus aureus and Corynebacterium diphtheriae do not typically cross the placenta. Choice D is incorrect because Listeria monocytogenes can indeed be transmitted through the placenta, unlike the other pathogens listed.

Correct Answer: B

Rationale: The correct answer is B: Zoonosis. Tularemia is primarily a zoonotic disease, meaning it is transmitted from animals to humans. The bacterium that causes tularemia, Francisella tularensis, commonly infects animals like rabbits, rodents, and ticks, which serve as reservoir hosts. Humans can get infected through direct contact with infected animals, insect bites, or contaminated water or soil. This zoonotic nature of tularemia distinguishes it from anthroponosis (A), which is transmitted only between humans, and sapronosis (C), which is transmitted through non-living environmental sources. Choice D is incorrect because there is a correct answer, which is zoonosis.

Correct Answer: A

Rationale: The correct answer is A: Sandfly. Cutaneous leishmaniasis is transmitted by the bite of infected sandflies. These tiny insects are known vectors for Leishmania parasites. Sandflies are active during dusk and night, feeding on blood from mammals, including humans. Tick (B), mosquito (C), and tsetse fly (D) are not vectors for Leishmania parasites. Ticks transmit diseases like Lyme disease, mosquitoes transmit diseases like malaria, and tsetse flies transmit African trypanosomiasis. Therefore, the correct vector for cutaneous leishmaniasis is the sandfly due to its specific role in transmitting the Leishmania parasite.