OpenStax Microbiology Test Bank

Correct Answer: C

Rationale: The correct answer is C: Binding of mast cell-fixed IgE. The Bezredka method involves introducing small amounts of the antigen to which the individual is allergic, leading to the binding of mast cell-fixed IgE. This process desensitizes the immune system and prevents anaphylactic shock by reducing the release of histamine and other mediators from mast cells. Rationale: 1. A: Stimulation of antigen-specific IgG2 is incorrect because the Bezredka method primarily targets IgE, not IgG2. 2. B: Stimulation of the immunological antigen tolerance is incorrect as this method aims to block the allergic response rather than induce tolerance. 3. D: Blocking of mast cell mediators synthesis is incorrect because the Bezredka method does not directly inhibit the synthesis of mast cell mediators, but rather blocks their release by binding IgE.

Correct Answer: B

Rationale: The Ziehl-Neelsen stain is specifically designed to detect acid-fast bacteria like Mycobacterium tuberculosis. It utilizes a carbol fuchsin dye that binds to the high lipid content in the cell wall of acid-fast bacteria, making them appear red under a microscope. This staining method is crucial for the diagnosis of tuberculosis and leprosy. Gram-positive bacteria (Choice A) are not detected by this stain since they have a different cell wall structure. Capsulated bacteria (Choice C) and fungal spores (Choice D) also have distinct characteristics that are not targeted by the Ziehl-Neelsen stain.

Correct Answer: A

Rationale: The correct answer is A because lipophilization is the process of removing water from cells under deep vacuum in a frozen state. Dehydration of the cell at a low temperature helps to preserve the cellular structure and components. Choice B is incorrect as hydration does the opposite of what lipophilization aims to achieve. Choice C is incorrect as lipophilization does not involve enriching cells with proteins. Choice D is incorrect as lipophilization does not involve removing protein content from cells.

Correct Answer: B

Rationale: The correct answer is B because lysozyme, lactoferrin, interferon, and complement are all humoral factors involved in natural resistance. Lysozyme and lactoferrin are antimicrobial proteins that help defend against pathogens. Interferon is a signaling protein that inhibits viral replication, while complement is a group of proteins that enhance the immune response by promoting inflammation and opsonization. Choices A, C, and D are incorrect: - Choice A mentions only macrophages, which are not humoral factors but rather phagocytic cells. - Choice C lists immune cells involved in adaptive immunity (B and T lymphocytes, NK cells) rather than humoral factors of natural resistance. - Choice D includes immunoglobulins, which are part of adaptive immunity, not natural resistance.

Correct Answer: A

Rationale: The correct answer is A: Treponema. Treponema pallidum is a spirochete bacterium that appears as long, thin, and spiral-shaped microorganisms with 8-12 regular coils under the microscope. This characteristic morphology is specific to Treponema species, making it the correct choice. Borrelia, Leptospira, and Vibrios have different shapes and arrangements under the microscope, making them incorrect choices in this scenario.