Which of the following bacteria is responsible for causing botulism?

Correct Answer: A

Rationale: The correct answer is A, Clostridium botulinum. This bacterium produces botulinum toxin, leading to botulism. It is commonly found in soil and improperly canned food. Clostridium tetani causes tetanus, Staphylococcus aureus causes food poisoning, and Salmonella enterica causes salmonellosis. Therefore, A is correct due to its association with botulism, while the other choices are incorrect for causing different diseases.

Correct Answer: D

Rationale: The correct answer is D, the rabies virus. Rabies virus has the widest infectious spectrum among the given choices because it can infect a wide range of mammals, including humans. This is due to its ability to infect nerve cells and spread throughout the central nervous system. The other choices have more limited infectious spectra. Anthrax bacillus primarily infects herbivores and humans, mumps virus infects mainly humans, and the causative agent of gonorrhea primarily infects humans through sexual contact. Therefore, the rabies virus is the correct answer as it has the broadest range of potential hosts.

Correct Answer: A

Rationale: The correct answer is A: Peroxidase and catalase. Peroxidase and catalase are enzymes that break down hydrogen peroxide into water and oxygen. Peroxidase helps in breaking down low levels of hydrogen peroxide, while catalase is crucial for breaking down high levels of hydrogen peroxide efficiently. This process is important for organisms to prevent damage from reactive oxygen species. Choices B, C, and D are incorrect: B: Oxygenase and hydroxylase are enzymes involved in different biochemical reactions and do not break down hydrogen peroxide. C: Cytochrome oxidase and cytochrome B5 are involved in electron transport chain reactions and not in breaking down hydrogen peroxide. D: Oxygenase and catalase are not correct as oxygenase is not involved in hydrogen peroxide breakdown, only catalase is.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Purple-stained diplococci suggest Gram-positive cocci. 2. Capsule presence is a characteristic of Streptococcus pneumoniae. 3. S. pneumoniae is known to form diplococci arrangements. 4. Therefore, the microorganism most likely present is Streptococcus pneumoniae. Summary: - B: Klebsiella pneumoniae is a Gram-negative rod, not a cocci. - C: Neisseria meningitidis is a Gram-negative diplococcus, not a capsule producer. - D: Escherichia coli is a Gram-negative rod, not a cocci or capsule producer.

Correct Answer: D

Rationale: The correct answer is D: Agglutination test type Gruber. This is because the Gruber agglutination test is not typically used for the serological identification of Yersinia pestis. The other options (A, B, C) are commonly used methods for serological identification of Y. pestis: A) Precipitation reaction involves the formation of a visible precipitate when Y. pestis antigen reacts with specific antibodies. B) Indirect hemagglutination test detects antibodies against Y. pestis by measuring the agglutination of red blood cells. C) Immunofluorescence test uses fluorescently labeled antibodies to detect specific antigens of Y. pestis. In summary, the Gruber agglutination test is not a standard method for serological identification of Yersinia pestis, unlike the other options provided.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria listed (Staphylococcus aureus, Escherichia coli, Clostridium botulinum) can produce toxins leading to food poisoning. Staphylococcus aureus produces heat-stable toxins causing rapid onset of symptoms. Escherichia coli can produce toxins like Shiga toxin leading to severe foodborne illness. Clostridium botulinum produces neurotoxins causing botulism. Choice A, B, and C are incorrect because each bacteria can produce toxins that are harmful if ingested.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Anopheles mosquitoes are the primary vectors for transmitting malaria. 2. They prefer stagnant water for breeding, common in tropical regions. 3. Culex mosquitoes primarily spread diseases like West Nile virus. 4. Aedes mosquitoes transmit diseases like Zika and dengue fever. 5. Mansonia mosquitoes are known for transmitting filarial diseases. Therefore, the correct answer is A (Anopheles), as they are specifically associated with spreading malaria.

Correct Answer: A

Rationale: Passive immunity is the transfer of pre-formed antibodies from one individual to another, providing immediate protection. This process does not involve the recipient's immune response, hence it is called passive. Active immunity, on the other hand, involves the individual's immune system producing its own antibodies after exposure to an antigen. Innate immunity refers to the body's natural defense mechanisms present from birth, not involving antibodies. Therefore, the correct answer is A: passive immunity.

Correct Answer: D

Rationale: The correct answer is D because enveloped viruses have a lipid bilayer envelope derived from the host cell membrane, which is a complex structure, not exhibiting any specific symmetry. Choice A (cubic symmetry) is incorrect as enveloped viruses do not have any specific geometric shape. Choice B (spiral symmetry) is incorrect as this type of symmetry is typically seen in non-enveloped viruses like helical viruses. Choice C (complex symmetry) is also incorrect as enveloped viruses do not exhibit a specific symmetrical pattern. Therefore, the correct answer is D because enveloped viruses do not have a defined symmetry and can vary in shape and structure.