Nokea
Lysozyme acts on the bacterial:
- A. cytoplasm
- B. cell wall
- C. nucleus
- D. capsule
Correct Answer: B
Rationale: The correct answer is B: cell wall. Lysozyme is an enzyme that targets the cell wall of bacteria by breaking down the peptidoglycan layer, leading to bacterial cell lysis. This action disrupts the structural integrity of the bacteria, ultimately causing their death. Choices A, C, and D are incorrect because lysozyme does not target the cytoplasm, nucleus, or capsule of bacteria. The primary function of lysozyme is to act on the cell wall, making option B the correct answer in this context.
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The spore in the cells of Clostridium tetani is located:
- A. Paracentrally
- B. Subterminally
- C. Centrally
- D. Terminally
Correct Answer: D
Rationale: The correct answer is D: Terminally. In Clostridium tetani, spores are located at the terminal end of the cell. This positioning helps the spores to be released easily when the cell lyses, aiding in the spread of the bacteria. Paracentrally (A) and centrally (C) would not be as efficient for spore release. Subterminally (B) is also incorrect as the spores are specifically located at the terminal end of the cell, not just near it.
Microscopic examination of pus sample taken from mandibular fistula canal and stained by Gram's method has revealed druses with gram-positive coloring in the center and cone-shaped structures with gram-negative coloring. Such morphology is characteristic of the agent of:
- A. Fusobacteriosis
- B. Actinomycosis
- C. Staphylococcal osteomyelitis
- D. Anaerobic infection
Correct Answer: B
Rationale: The correct answer is B: Actinomycosis. Actinomyces is a gram-positive bacterium that forms sulfur granules (druses) with gram-positive coloring in the center and filamentous structures resembling cones with gram-negative coloring. This morphology is characteristic of Actinomyces species. Fusobacteriosis (choice A) typically presents with gram-negative rods. Staphylococcal osteomyelitis (choice C) is caused by gram-positive staphylococci, not Actinomyces. Anaerobic infections (choice D) can be caused by various bacteria, but the specific morphology described in the question matches Actinomyces, making choice B the correct answer.
The cell surface of pathogenic gram-negative bacteria can be covered in villi and cilia. What function do these structures have?
- A. RNA exchange between cells
- B. Inhibition of complement activity
- C. Bacterial adhesion to the surface of the host cells, conjugation
- D. Resistance to antibody opsonization
Correct Answer: C
Rationale: The correct answer is C: Bacterial adhesion to the surface of the host cells, conjugation. Villi and cilia on the cell surface of pathogenic bacteria help in bacterial adhesion to host cells, facilitating the process of infection. Conjugation is the transfer of genetic material between bacterial cells, which can be aided by these structures. The other choices are incorrect because RNA exchange between cells (A) is typically facilitated by different structures like pili, inhibition of complement activity (B) is not related to the function of villi and cilia, and resistance to antibody opsonization (D) is usually achieved through other mechanisms such as capsule formation.
Which of the following bacteria is responsible for causing the disease diphtheria?
- A. Bacillus anthracis
- B. Corynebacterium diphtheriae
- C. Streptococcus pneumoniae
- D. Escherichia coli
Correct Answer: B
Rationale: The correct answer is B: Corynebacterium diphtheriae. This bacterium produces a toxin that causes diphtheria. It forms a grayish membrane in the throat, leading to difficulty breathing. Bacillus anthracis (Choice A) causes anthrax, Streptococcus pneumoniae (Choice C) causes pneumonia, and Escherichia coli (Choice D) causes various infections but not diphtheria.
Member of a family ‘Reoviruses' that causes diarrhea in infants is called:
- A. Rotavirus
- B. Congovirus
- C. Hepadnavirus
- D. Picornavirus
Correct Answer: A
Rationale: The correct answer is A: Rotavirus. Rotavirus is a member of the Reoviridae family known for causing diarrhea in infants. It infects the lining of the small intestine, leading to symptoms like vomiting and watery diarrhea.
Rationale:
1. Rotavirus is specifically known for causing diarrhea in infants.
2. Reoviruses are a family of viruses to which rotavirus belongs.
3. Congovirus (B), Hepadnavirus (C), and Picornavirus (D) do not belong to the Reoviridae family and are not associated with causing diarrhea in infants.
In summary, choice A is correct as it aligns with the characteristics of the given family of viruses and their associated symptoms, while choices B, C, and D are incorrect as they do not fit these criteria.