Which bacteria is responsible for causing the disease known as cholera?

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a bacterium that produces a toxin leading to severe diarrhea and dehydration. Clostridium botulinum (A) causes botulism, Salmonella enterica (C) causes salmonellosis, and Escherichia coli (D) can cause various illnesses but not cholera. Vibrio cholerae is the only bacteria specifically known for causing cholera.

Correct Answer: C

Rationale: The correct answer is C: Salmonella. This bacterium should be handled in a Biosafety Level 2 facility due to its potential to cause disease in humans. Salmonella is a pathogenic bacterium that can cause foodborne illnesses and infections. Handling it in a Biosafety Level 2 facility ensures proper containment and protection of personnel. A: Micrococcus luteus and B: Bacillus subtilis are common environmental bacteria that do not pose significant risks to human health, so they can be safely handled in lower biosafety levels. D: Staphylococcus epidermidis is a common skin commensal bacterium that is generally not considered highly pathogenic, so it does not require Biosafety Level 2 containment.

Correct Answer: D

Rationale: The correct answer is D: Hypersensitivity of delayed type. The symptoms described occur 5-10 days after exposure to the antigen, consistent with a delayed hypersensitivity reaction. This type of reaction involves T cells and is characterized by cell-mediated immune response, leading to inflammation and tissue damage. Choices A, B, and C are incorrect because they are associated with different mechanisms of allergic reactions. Immunocomplex reactions (choice A) involve antigen-antibody complexes depositing in tissues, immediate hypersensitivity reactions (choice B) involve IgE-mediated mast cell degranulation, and cytotoxic reactions (choice C) involve antibodies targeting specific cells for destruction.

Correct Answer: A

Rationale: Neisseria gonorrhoeae is the correct answer because it is the specific bacterium responsible for causing gonorrhea. It is a sexually transmitted infection that primarily affects the genital tract. Neisseria gonorrhoeae is transmitted through sexual contact and can lead to symptoms such as painful urination, discharge, and pelvic pain. Chlamydia trachomatis (Choice B) is another sexually transmitted bacterium, but it causes chlamydia, not gonorrhea. Mycobacterium tuberculosis (Choice C) is responsible for tuberculosis, a different infectious disease that primarily affects the lungs. Treponema pallidum (Choice D) causes syphilis, another sexually transmitted infection that presents with distinct symptoms from gonorrhea. Therefore, Neisseria gonorrhoeae is the correct choice for causing gonorrhea due to its specific association with this particular infection.

Correct Answer: B

Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by this specific bacterium due to its production of cholera toxin, leading to severe watery diarrhea. Shigella dysenteriae causes dysentery, Salmonella enterica causes salmonellosis, and Clostridium perfringens causes food poisoning, none of which present with the characteristic symptoms of cholera.

Correct Answer: C

Rationale: Rationale: C is the correct answer because antibodies formed against Mycobacterium tuberculosis are not protective. They do not efficiently clear the infection due to the bacterium's ability to evade the immune response by residing intracellularly in macrophages. Antibodies play a minimal role in controlling tuberculosis compared to cell-mediated immunity. Summary: A is incorrect because Mycobacterium tuberculosis does contain mycolic acid in its cell wall. B is incorrect because the pathogen can indeed live intracellularly in macrophages. D is incorrect as C is the correct answer.

Correct Answer: B

Rationale: The correct answer is B: H antigen. Flagellar antigen is typically referred to as the H antigen in bacteria. Flagella are the whip-like structures used for movement in bacteria, and the H antigen is specifically associated with the flagella. The other choices (A: D antigen, C: K antigen, D: F antigen) are not related to flagella in bacteria and are commonly associated with other types of antigens in bacterial classification.

Correct Answer: A

Rationale: Step 1: Viruses can have either DNA or RNA, not both, hence they have only one type of nucleic acid. Step 2: The extracellular form of viruses is called virion, not viroid. Step 3: Viruses are obligate intracellular parasites, meaning they rely on host cells for replication. Step 4: Viruses are measured in nanometers, not micrometers. Therefore, the correct answer is A.

Correct Answer: B

Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is important for controlling air quality as it can degrade a wide range of organic compounds present in the air, helping to maintain a clean and healthy environment. Alpha and beta-hemolytic streptococci (Choice A) are not typically associated with air quality control. E. coli (Choice C) and Salmonella spp. (Choice D) are more commonly found in water and food sources, not air, making them incorrect choices for this question. Pseudomonas aeruginosa's ability to break down organic matter in the air makes it the most suitable option for maintaining sanitary air quality.