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Which bacteria is responsible for causing 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 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.
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N. Meningitidis grows on
- A. Levine agar
- B. Lowenstein-Jensen agar
- C. TCBS agar
- D. Chocolate agar
Correct Answer: D
Rationale: The correct answer is D: Chocolate agar. Neisseria meningitidis is a fastidious organism that requires enriched media for growth. Chocolate agar contains heat-treated blood that provides essential nutrients for the growth of N. meningitidis. The other choices, A: Levine agar, B: Lowenstein-Jensen agar, and C: TCBS agar, do not provide the specific nutrients required for the growth of N. meningitidis. Therefore, only choice D, Chocolate agar, supports the growth of N. meningitidis due to its enriched composition.
For measles virus is true that:
- A. There is no outer membrane
- B. Contains singles-stranded RNA with negative polarity
- C. Belongs to family Togaviridae
- D. Cannot be grown on cell cultures
Correct Answer: B
Rationale: The correct answer is B: Contains single-stranded RNA with negative polarity. Measles virus is an enveloped virus with a single-stranded RNA genome that is negative-sense. This means it must first be transcribed into positive-sense RNA before it can be translated. Choice A is incorrect as the measles virus does have an outer envelope. Choice C is incorrect as measles virus belongs to the family Paramyxoviridae, not Togaviridae. Choice D is incorrect as measles virus can be grown on cell cultures, specifically on Vero cells.
Laboratory diagnosis of rabies includes all of these except:
- A. Looking for Negri bodies
- B. Intracerebrally infected mice
- C. Looking for Ernst-Babes granules
- D. Immunofluorescence method
Correct Answer: C
Rationale: The correct answer is C: Looking for Ernst-Babes granules. Laboratory diagnosis of rabies typically involves looking for Negri bodies in the brain tissue, intracerebrally infecting mice for virus isolation, and using immunofluorescence method to detect viral antigens. Ernst-Babes granules are not associated with rabies virus and are not used in the diagnosis of rabies. Therefore, choice C is incorrect.
Which of the following best describes the function of bacterial capsules?
- A. Enhance bacterial motility
- B. Enable bacterial adherence to surfaces
- C. Prevent bacterial DNA replication
- D. Protect bacteria from desiccation
Correct Answer: B
Rationale: The correct answer is B: Enable bacterial adherence to surfaces. Bacterial capsules are a protective layer outside the cell wall that helps bacteria adhere to surfaces and evade host immune responses. This allows bacteria to colonize and infect host tissues.
A: Enhancing bacterial motility is typically associated with flagella, not capsules.
C: Bacterial DNA replication is not directly affected by capsules.
D: Bacterial capsules do play a role in protecting bacteria from desiccation by providing a barrier against drying out. However, the primary function is enabling adherence to surfaces.
The cytoplasmic membrane in bacteria is composed of:
- A. Phospholipids, glycerol and glycolipids
- B. Lipopolysaccharides
- C. Lipopolysaccharides and peptidoglycan
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A because the cytoplasmic membrane in bacteria is primarily composed of phospholipids, glycerol, and glycolipids. Phospholipids form the basic structure of the membrane, with glycerol serving as the backbone and glycolipids present on the outer surface. Lipopolysaccharides (choice B) are primarily found in the outer membrane of Gram-negative bacteria, not the cytoplasmic membrane. Choice C is incorrect because peptidoglycan is a component of the bacterial cell wall, not the cytoplasmic membrane. Choice D is incorrect as the cytoplasmic membrane in bacteria is indeed composed of phospholipids, glycerol, and glycolipids.