Nokea
A wound culture from a patient with an infected ulcer revealed Gram-positive rods with terminal spores. What is the most likely causative agent?
- A. Clostridium perfringens
- B. Bacillus anthracis
- C. Clostridium tetani
- D. Bacillus cereus
Correct Answer: A
Rationale: Step-by-step rationale:
1. Gram-positive rods with terminal spores suggest Clostridium genus.
2. Terminal spores are characteristic of Clostridium perfringens.
3. C. perfringens is known to cause wound infections.
4. Therefore, the most likely causative agent is Clostridium perfringens.
Summary:
A: Clostridium perfringens is correct due to its characteristic features and association with wound infections.
B: Bacillus anthracis does not typically form terminal spores.
C: Clostridium tetani causes tetanus, not wound infections.
D: Bacillus cereus does not produce terminal spores like Clostridium perfringens.
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How the prepared immunofluorescence slide should be examined?
- A. Under the fluorescence microscope using x100 oil immersion objective
- B. Under light microscope using x100 oil immersion objective
- C. Using electron microscopy
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A because immunofluorescence slides are examined under a fluorescence microscope with a x100 oil immersion objective. This is because immunofluorescence relies on the detection of fluorescently labeled antibodies, which emit light when excited by a specific wavelength. Using a fluorescence microscope allows for visualization of these labeled antibodies at high magnification and resolution, enabling precise examination of cellular structures and protein localization. Choice B is incorrect as light microscopes are not suitable for visualizing fluorescence. Choice C is incorrect as electron microscopes use electrons, not light, for imaging, which is not compatible with immunofluorescence. Choice D is incorrect as there is a specific method for examining immunofluorescence slides.
Langerhans cells, which play a role in defense against microbes, are located in the:
- A. epidermis
- B. dermis
- C. hypodermis
- D. subcutaneous layer
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.
While studying a microslide obtained from the punctuate of a regional lymph node and stained by Romanovsky-Giemsa method a physician revealed some light pink thin microorganisms with 12-14 regular spiral coils and pointed ends, up to 10-13 micrometer long. This might be the causative agent of the following disease:
- A. Syphilis
- B. Trypanosomiasis
- C. Leptospirosis
- D. Relapsing fever
Correct Answer: D
Rationale: The correct answer is D: Relapsing fever. The description matches Borrelia species, the causative agent of relapsing fever. The thin, spiral-shaped microorganisms with pointed ends and specific length are characteristic of Borrelia. The number of coils and size mentioned also align with Borrelia morphology. Relapsing fever is transmitted by tick bites and manifests as recurring febrile episodes.
Incorrect choices:
A: Syphilis - Syphilis is caused by Treponema pallidum, which is not spiral-shaped.
B: Trypanosomiasis - Trypanosomiasis is caused by Trypanosoma species, which are not spiral-shaped.
C: Leptospirosis - Leptospirosis is caused by Leptospira species, which are not spiral-shaped and do not match the specific description provided.
A male patient has been diagnosed with gastric ulcer. Bacteriological examination of biopsy material from the affected part of stomach revealed small colonies of gram-negative, oxide reductase-positive flexibacteria that grew on the chocolate agar on the fifth day. Which of the following microorganisms is the most likely causative agent?
- A. Helicobacter pylori
- B. Campilobacter jejuni
- C. Campilobacter fetus
- D. Mycoplasma hominis
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.
A 16-year-old adolescent was vaccinated with DTP. In eight days there was stiffness and pain in the joints, subfebrile temperature, urticarial skin eruption, enlargement of inguinal, cervical lymph nodes and spleen. What kind of allergic reaction is observed?
- A. Immunocomplex
- B. Hypersensitivity of immediate type
- C. Cytoxic
- D. Hypersensitivity of delayed type
Correct Answer: D
Rationale: The correct answer is D: Hypersensitivity of delayed type. The symptoms described occur 5-10 days after exposure to the antigen, consistent with a delayed hypersensitivity reaction. This type of reaction involves T cells and is characterized by cell-mediated immune response, leading to inflammation and tissue damage. Choices A, B, and C are incorrect because they are associated with different mechanisms of allergic reactions. Immunocomplex reactions (choice A) involve antigen-antibody complexes depositing in tissues, immediate hypersensitivity reactions (choice B) involve IgE-mediated mast cell degranulation, and cytotoxic reactions (choice C) involve antibodies targeting specific cells for destruction.