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Which bacteria is known for causing the disease cholera?
- A. Shigella dysenteriae
- B. Vibrio cholerae
- C. Salmonella enterica
- D. Clostridium perfringens
Correct Answer: B
Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by Vibrio cholerae, a gram-negative bacterium that produces a toxin leading to severe watery diarrhea. Shigella dysenteriae causes dysentery, not cholera. Salmonella enterica causes salmonellosis, not cholera. Clostridium perfringens is associated with food poisoning, not cholera. In summary, Vibrio cholerae is the correct answer because it is the specific bacterium known to cause cholera, while the other choices are associated with different diseases.
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The most common congenital infection worldwide is due to:
- A. CMV
- B. Listeria monocytogenes
- C. Rubella Virus
- D. Syphilis
Correct Answer: A
Rationale: The correct answer is A: CMV (Cytomegalovirus). CMV is the most common congenital infection worldwide due to its high prevalence and ability to be transmitted from mother to fetus during pregnancy. It can lead to serious complications such as hearing loss, developmental delays, and vision problems in newborns. Listeria monocytogenes (B) is a foodborne pathogen, not typically associated with congenital infections. Rubella Virus (C) can cause congenital rubella syndrome but is less common globally compared to CMV. Syphilis (D) can also be transmitted from mother to fetus, but its prevalence and impact on congenital infections are lower compared to CMV.
Bacterial endotoxins are:
- A. proteins in the cell wall
- B. secreted into the environment
- C. components of the gram-positive cell wall
- D. components of the gram-negative cell wall
Correct Answer: D
Rationale: The correct answer is D: components of the gram-negative cell wall. Bacterial endotoxins are lipopolysaccharides found in the outer membrane of gram-negative bacteria. They are released upon bacterial cell lysis and can cause severe immune responses.
A: Proteins in the cell wall - This is incorrect because endotoxins are not proteins but rather lipopolysaccharides.
B: Secreted into the environment - Endotoxins are not actively secreted but are released upon cell death or lysis.
C: Components of the gram-positive cell wall - Gram-positive bacteria do not have an outer membrane with lipopolysaccharides, so endotoxins are not found in the gram-positive cell wall.
Chemically an antigen may be:
- A. Lipid
- B. Protein
- C. Polysaccharide
- D. Any of these
Correct Answer: D
Rationale: The correct answer is D because antigens can be composed of lipids, proteins, or polysaccharides. Antigens are molecules that can elicit an immune response in the body. They can be diverse in their chemical composition, leading to the recognition and response by the immune system. Therefore, the correct choice is D as antigens can be any of these chemical components. Choices A, B, and C are incorrect because they each represent a possible chemical composition of antigens, but the flexibility of antigens to be made up of any of these components makes D the most accurate choice.
What is the function of bacterial flagella?
- A. Protein synthesis
- B. Motility
- C. Adhesion to surfaces
- D. DNA replication
Correct Answer: B
Rationale: The correct answer is B: Motility. Bacterial flagella function in providing motility to bacteria, allowing them to move towards nutrients or away from harmful substances. Flagella are long, whip-like appendages that rotate to propel the bacteria through their environment.
Incorrect choices:
A: Protein synthesis - Bacterial flagella are not involved in protein synthesis.
C: Adhesion to surfaces - While some bacteria use flagella for attachment, their main function is not adhesion.
D: DNA replication - Flagella do not play a role in DNA replication, which occurs in the bacterial cell's nucleus.
Most reliable test for detection of acute hepatitis A infection is
- A. Western blot assay for IgG anti-HAV in serum
- B. ELISA test for IgM anti-HAV in serum and HAV-Ag in stools
- C. ELISA test for IgG anti-HAV in serum
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: ELISA test for IgM anti-HAV in serum and HAV-Ag in stools. This test is the most reliable for detecting acute hepatitis A infection because IgM antibodies are produced early in the infection, indicating an active infection. Detection of HAV antigen in stools also confirms active viral shedding.
A: Western blot assay for IgG anti-HAV in serum is not the most reliable for acute infection detection as IgG antibodies are produced later in the infection and indicate past exposure or immunity.
C: ELISA test for IgG anti-HAV in serum is not the most reliable for acute infection detection as IgG antibodies are produced later in the infection and indicate past exposure or immunity.
D: None of the above is incorrect as option B is the most appropriate choice for detecting acute hepatitis A infection.