Nokea
A fecal sample from a patient with diarrhea revealed cysts with four nuclei. What is the most likely causative agent?
- A. Entamoeba histolytica
- B. Giardia lamblia
- C. Trichomonas vaginalis
- D. Balantidium coli
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This is because the presence of cysts with four nuclei is characteristic of Entamoeba histolytica, a protozoan parasite that causes amoebic dysentery. Entamoeba histolytica cysts contain four nuclei, distinguishing them from other pathogens. Giardia lamblia and Trichomonas vaginalis are not associated with cysts containing four nuclei. Balantidium coli is a ciliated protozoan that does not typically form cysts with multiple nuclei. In summary, the unique feature of four nuclei in the cysts points towards Entamoeba histolytica as the most likely causative agent of the diarrhea in this patient.
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On a certain territory mass death of rodents was registered. It was suspected that their death might have been caused by plague. What serological reaction should be applied for quick identification of antigen of the causative agent of this epizooty?
- A. Precipitation
- B. Agglutination
- C. Passive hemagglutination
- D. Complement binding
Correct Answer: B
Rationale: The correct answer is B: Agglutination. During a suspected plague outbreak, agglutination testing is used to quickly identify the antigen of the causative agent. In this test, specific antibodies are added to a sample containing the suspected antigen. If the antigen is present, it will clump together (agglutinate) with the antibodies, indicating a positive result. This method is rapid and efficient for identifying the presence of the plague-causing agent.
Choice A: Precipitation involves the formation of a visible precipitate when antigen and antibody react, but it is not as quick or specific as agglutination for identifying the antigen in this scenario.
Choice C: Passive hemagglutination is a variation of agglutination that uses red blood cells as carriers for antigens or antibodies. While it can be useful in certain situations, it is not typically the first choice for rapid identification of plague antigen.
Choice D: Complement binding is a different type of
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.
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.
Mycoplasma species lack:
- A. Cell wall
- B. Plasma membrane
- C. DNA
- D. Ribosomes
Correct Answer: A
Rationale: The correct answer is A: Cell wall. Mycoplasma species lack a cell wall, making them unique among bacteria. This is because they have a flexible cell membrane that provides structural support instead of a rigid cell wall. The absence of a cell wall allows them to be pleomorphic and gives them resistance to certain antibiotics targeting cell wall synthesis. Plasma membrane (B), DNA (C), and ribosomes (D) are present in Mycoplasma species, so they are not the correct answer.
Viruses are characterised by:
- A. They have only one type of nucleic acid
- B. Their extracellular form is referred as “viroidâ€
- C. They are optional intracellular parasites
- D. Their size is measured in micrometers
Correct Answer: A
Rationale: Step 1: Viruses can have either DNA or RNA, not both, hence they have only one type of nucleic acid.
Step 2: The extracellular form of viruses is called virion, not viroid.
Step 3: Viruses are obligate intracellular parasites, meaning they rely on host cells for replication.
Step 4: Viruses are measured in nanometers, not micrometers.
Therefore, the correct answer is A.