Nokea
Nigrosin is a stain used in:
- A. simple staining
- B. gram staining
- C. negative staining
- D. acid-fast staining
Correct Answer: C
Rationale: Nigrosin is used in negative staining, where the background is stained instead of the cells themselves. This technique helps highlight the morphology and structure of cells that may be damaged by traditional staining methods. Nigrosin is negatively charged and repels the negatively charged bacterial cells, resulting in a clear halo around the cells. This process is particularly useful for observing capsules and determining cell size and shape. The other options are incorrect because simple staining uses a single dye to color the entire cell, gram staining involves a series of dyes to differentiate between gram-positive and gram-negative bacteria, and acid-fast staining is used to detect acid-fast organisms like Mycobacterium.
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Allergies to sea food, eggs, etc are an example of:
- A. Type 1 hypersensitivity reaction
- B. Type 2 hypersensitivity reaction
- C. Type 3 hypersensitivity reaction
- D. Type 4 hypersensitivity reaction
Correct Answer: A
Rationale: The correct answer is A: Type 1 hypersensitivity reaction. In this type of reaction, allergens trigger the production of IgE antibodies, leading to mast cell and basophil degranulation and release of inflammatory mediators like histamine. This causes immediate allergic symptoms. Seafood and eggs are common allergens that can elicit this response.
B: Type 2 hypersensitivity reaction involves antibodies targeting cell surface or extracellular matrix antigens, leading to cell destruction or dysfunction. This is not the mechanism in seafood or egg allergies.
C: Type 3 hypersensitivity reaction involves immune complex deposition in tissues, leading to inflammation and tissue damage. This is not the mechanism in seafood or egg allergies.
D: Type 4 hypersensitivity reaction is cell-mediated and involves T cells causing inflammation and tissue damage. This is not the mechanism in seafood or egg allergies.
The compact structure in which the genome of the bacteria is located is called:
- A. Nucleoid
- B. Nucleotide
- C. ATP
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Nucleoid. The bacterial genome is located in the nucleoid, a region within the bacterial cell where the genetic material is condensed and organized. This structure is not the same as a nucleus found in eukaryotic cells. The other choices (B: Nucleotide and C: ATP) are incorrect because nucleotide refers to a building block of DNA or RNA, and ATP is a molecule used for energy transfer in cells, neither of which specifically houses the bacterial genome. Choice D: None of the above is incorrect as well, as the correct term for the compact structure containing the bacterial genome is the nucleoid.
A child cut his leg with a piece of glass while playing and was brought to the clinic for the injection of tetanus toxoid. In order to prevent the development of anaphylactic shock the serum was administered by Bezredka method. What mechanism underlies this method of desensitization of the body?
- A. Binding of IgE fixed to the mast cells
- B. Blocking the mediator synthesis in the mast cells
- C. Stimulation of immune tolerance to the antigen
- D. Stimulation of the synthesis of antigenspecific IgG
Correct Answer: A
Rationale: The correct answer is A: Binding of IgE fixed to the mast cells. The Bezredka method involves injecting small, gradually increasing doses of the antigen (tetanus toxoid) to desensitize the body and prevent anaphylactic shock. This process works by binding the IgE antibodies fixed to mast cells, thereby reducing the release of allergic mediators like histamine. This prevents the cascade of events that lead to anaphylactic shock.
Choice B (Blocking the mediator synthesis in the mast cells) is incorrect because the Bezredka method does not block mediator synthesis but rather prevents the release of mediators by binding IgE.
Choice C (Stimulation of immune tolerance to the antigen) is incorrect as the Bezredka method does not primarily focus on inducing immune tolerance but rather on preventing anaphylactic reactions.
Choice D (Stimulation of the synthesis of antigen-specific IgG) is incorrect because the Bezredka method targets IgE antibodies on mast cells
A smear of a patient's sputum suspected for tuberculosis was prepared and stained. The smear showed red bacilli against a blue background. What staining method was used?
- A. Ziehl-Neelsen
- B. Gram
- C. Giemsa
- D. Neisser
Correct Answer: A
Rationale: The correct answer is A: Ziehl-Neelsen staining method. This method is used to detect acid-fast bacteria like Mycobacterium tuberculosis. Step-by-step rationale: 1. Acid-fast bacteria resist decolorization with acid-alcohol. 2. The red bacilli seen in the smear indicate acid-fast bacteria. 3. Ziehl-Neelsen stain uses carbol fuchsin to stain acid-fast bacteria red. 4. The blue background is likely the counterstain methylene blue. Incorrect choices: B: Gram stain is for categorizing bacteria into Gram-positive or Gram-negative, not specific for acid-fast bacteria. C: Giemsa stain is used for blood films and detecting parasites, not acid-fast bacteria. D: Neisser stain is not a standard microbiological staining method.
Which bacteria is responsible for causing the disease known as whooping cough?
- A. Clostridium botulinum
- B. Bordetella pertussis
- C. Streptococcus pneumoniae
- D. Neisseria meningitidis
Correct Answer: B
Rationale: The correct answer is B: Bordetella pertussis. This bacterium causes whooping cough by infecting the respiratory tract. It produces toxins that lead to severe coughing fits characteristic of the disease. Clostridium botulinum (A) causes botulism, Streptococcus pneumoniae (C) causes pneumonia, and Neisseria meningitidis (D) causes meningitis, not whooping cough. B. pertussis is the only bacterium specifically associated with whooping cough.