Microbiology Chapter 13 Test Bank

Correct Answer: A

Rationale: The correct answer is A: Helicobacter pylori. This bacterium is the most likely causative agent of gastric ulcers. Here's the rationale: 1. Helicobacter pylori is commonly associated with gastric ulcers. 2. It is a gram-negative bacterium that grows on chocolate agar and is oxide reductase-positive. 3. The slow growth on the fifth day is characteristic of H. pylori. 4. Campylobacter jejuni and Campylobacter fetus are not typically associated with gastric ulcers. 5. Mycoplasma hominis is a bacterium that lacks a cell wall and is not commonly found in gastric ulcers.

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.

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.

Correct Answer: A

Rationale: The correct answer is A: epidermis. Langerhans cells are a type of immune cell found in the epidermis, the outermost layer of the skin. They play a crucial role in the defense against microbes by capturing and presenting antigens to activate the immune system. The dermis (B), hypodermis (C), and subcutaneous layer (D) are located deeper in the skin and do not contain Langerhans cells. Therefore, the epidermis is the correct location for these immune cells to carry out their defensive functions.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. This is because Pseudomonas is a Gram-negative rod, oxidase-positive, and non-lactose fermenter. These characteristics are typical of Pseudomonas species. B: Escherichia coli is a Gram-negative rod but is lactose fermenter and usually oxidase-negative. C: Klebsiella pneumoniae is a Gram-negative rod, non-lactose fermenter, but is usually oxidase-negative. D: Shigella dysenteriae is a Gram-negative rod, non-lactose fermenter, but is usually oxidase-negative and is more associated with causing shigellosis rather than deep tissue infections.