Nokea
Which is NOT an antigen-presenting cell (or APC)?
- A. B cell
- B. Polymorphonuclear leukocyte
- C. Dendritic cell
- D. All of the above
Correct Answer: B
Rationale: The correct answer is B: Polymorphonuclear leukocyte. APCs are specialized immune cells that present antigens to T cells. B cells and dendritic cells are classic examples of APCs, as they can efficiently present antigens. Polymorphonuclear leukocytes, such as neutrophils, are not considered traditional APCs because they are primarily involved in phagocytosis and killing of pathogens rather than antigen presentation. Therefore, they do not play a significant role in initiating adaptive immune responses. The incorrect choices are A (B cell) and C (Dendritic cell) because they are both well-known antigen-presenting cells in the immune system. Choice D (All of the above) is incorrect because B cells and dendritic cells are indeed antigen-presenting cells.
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Broadspectrum antibiotics can cause various complications, including intestinal candidiasis. What drug is used for treatment of this complication?
- A. Nystatin
- B. Griseofulvin
- C. Undecyne
- D. Amphotericin B
Correct Answer: A
Rationale: The correct answer is A: Nystatin. Nystatin is specifically used to treat intestinal candidiasis because it targets and eliminates the Candida species responsible for the infection. It is not absorbed systemically, acting only locally in the gastrointestinal tract. Griseofulvin (B) is mainly used to treat fungal skin infections, not intestinal candidiasis. Undecyne (C) is an antifungal agent used for skin infections, not for intestinal candidiasis. Amphotericin B (D) is a potent antifungal agent used for systemic fungal infections, not specifically for intestinal candidiasis.
Capsuliferous bacteria has been detected during microbiological inspection of crude drugs. What method of staining has been used to detect capsules?
- A. Burri-Gins
- B. Ziehl-Neelsen
- C. Neisser
- D. Gram
Correct Answer: A
Rationale: The correct answer is A: Burri-Gins. This staining method specifically targets the detection of capsules in bacteria. It involves staining the capsules with crystal violet and the background with safranin. This staining technique helps visualize the capsules as a distinct halo around the bacteria.
Summary:
- Choice B (Ziehl-Neelsen) is used for acid-fast staining to detect Mycobacterium species.
- Choice C (Neisser) is used for staining Neisseria species.
- Choice D (Gram) is a common staining method used to differentiate bacteria based on cell wall composition (Gram-positive and Gram-negative), but it does not specifically target capsules.
A smear of sputum from the patient with suspected lobar pneumonia was stained with the use of the following stains and reagents: solution of gentian violet, Lugol's solution, 96o alcohol, water-magenta. What staining method was applied in this case?
- A. Gram
- B. Ziehl-Nielsen
- C. Romanovsky
- D. Neisser
Correct Answer: A
Rationale: The correct answer is A: Gram staining method. This method involves staining with gentian violet, followed by Lugol's solution, 96% alcohol decolorization, and counterstaining with safranin or water-magenta. This staining sequence allows for the differentiation of bacteria based on their cell wall composition. In the case of lobar pneumonia, the causative agent is typically a bacterium with a cell wall that retains the crystal violet stain after decolorization with alcohol, indicating a Gram-positive bacterium.
Summary of Incorrect Choices:
B: Ziehl-Nielsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for lobar pneumonia.
C: Romanovsky staining is primarily used in the identification of blood cells and blood parasites, not for bacteria.
D: Neisser staining is not a commonly used staining method in microbiology for bacterial identification.
Which bacteria are known to produce an endotoxin that can cause septic shock?
- A. Salmonella enterica
- B. Escherichia coli
- C. Pseudomonas aeruginosa
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all three bacteria (Salmonella enterica, Escherichia coli, Pseudomonas aeruginosa) are known to produce endotoxins, specifically lipopolysaccharides in their cell walls. Endotoxins are released upon bacterial cell death and can trigger an immune response, leading to septic shock. Salmonella and E. coli are common causes of bacterial infections, while Pseudomonas is associated with nosocomial infections. Therefore, all of the above choices are correct in terms of producing endotoxins that can cause septic shock. Choices A, B, and C are incorrect individually because they do not encompass all the bacteria known to produce endotoxins that can lead to septic shock.
A patient being treated in the burns department has suppurative complication. The pus is of bluish- green color that is indicative of infection caused by Pseudomonas aeruginosa. What factor is typical for this causative agent?
- A. Gram-negative stain
- B. Presense of spores
- C. Coccal form
- D. Cell pairing
Correct Answer: A
Rationale: The correct answer is A: Gram-negative stain. Pseudomonas aeruginosa is a gram-negative bacterium, as indicated by the bluish-green pus color. This bacterium has an outer membrane that retains the crystal violet stain, making it appear pink/red after the counterstain with safranin in Gram staining. The other choices are incorrect because Pseudomonas aeruginosa does not typically form spores (B), has a rod-shaped morphology rather than a coccal form (C), and does not exhibit cell pairing (D).