Nokea
Microscopic examination of a smear from a patient with diphtheria revealed dark blue-staining granules at the ends of rod-shaped bacteria. What staining technique was likely used?
- A. Neisser's staining
- B. Ziehl-Neelsen staining
- C. Gram staining
- D. Giemsa staining
Correct Answer: A
Rationale: The correct answer is A: Neisser's staining. Neisser's staining is used to detect metachromatic granules in bacteria, which appear as dark blue-staining granules at the ends of rod-shaped bacteria in diphtheria. This technique specifically targets these granules, making it ideal for identifying Corynebacterium diphtheriae, the causative agent of diphtheria. Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, Gram staining is for classifying bacteria based on cell wall composition, and Giemsa staining is used for detecting parasites and certain blood cells, making them incorrect for identifying granules in diphtheria.
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Which of the following characteristics does not refer to the flu vaccine
- A. it is a recommended vaccine
- B. it is a subunit vaccine
- C. it is administered parenterally
- D. it stimulates mainly the local immunity
Correct Answer: D
Rationale: The correct answer is D because the flu vaccine primarily stimulates systemic immunity rather than local immunity. It is administered parenterally (C) as it is injected into the body. It is a subunit vaccine (B) as it contains only specific antigens of the virus. It is a recommended vaccine (A) due to its effectiveness in preventing influenza. In summary, D is the correct choice as the flu vaccine mainly targets systemic immunity, not local immunity, unlike the other characteristics listed.
Granulomatosis infantiseptica is caused by:
- A. Staphylococcus aureus
- B. Mycobacterium tuberculosis
- C. Listeria monocytogenes
- D. All of the above
Correct Answer: C
Rationale: Granulomatosis infantiseptica is commonly caused by Listeria monocytogenes, a bacterium known to infect newborns. It can lead to granulomatous lesions in various organs. Staphylococcus aureus and Mycobacterium tuberculosis are not typical causes of this condition in infants. Choice D is incorrect as it suggests all listed bacteria are responsible, which is not accurate. Therefore, the correct answer is C as Listeria monocytogenes is the specific pathogen associated with granulomatosis infantiseptica.
Factors that can increase the chances of vaginitis are:
- A. urinary blockage, drug use, and stress
- B. use of antibiotics, pregnancy, and menopause
- C. puberty, exposure to HPV, and smoking/tobacco use
- D. menopause, stress, and steroid use
Correct Answer: B
Rationale: The correct answer is B. Vaginitis is often caused by an imbalance in vaginal flora. Antibiotics can disrupt the natural balance, leading to overgrowth of harmful bacteria or yeast. Pregnancy alters hormone levels, making the vagina more susceptible to infection. Menopause decreases estrogen levels, thinning the vaginal walls and reducing beneficial bacteria.
A: Urinary blockage does not directly relate to vaginitis. Drug use and stress may weaken the immune system but are not direct causes of vaginitis.
C: Puberty, HPV exposure, and smoking/tobacco use do not directly increase the chances of vaginitis. HPV is a viral infection, not a direct cause of vaginitis.
D: While menopause can increase the risk of vaginitis due to hormonal changes, stress and steroid use are not primary factors in developing vaginitis.
Which of the following pathogenic mechanisms are not typical for autoimmune reactions?
- A. Decreased functional activity of T-suppressors
- B. Loss of tolerance for T-helpers and B-lymphocytes
- C. Ag released by normally isolated tissues
- D. Formation of CD4+ cells
Correct Answer: D
Rationale: The correct answer is D, Formation of CD4+ cells. In autoimmune reactions, CD4+ cells are actually involved in the immune response. Here's the rationale:
1. CD4+ cells are helper T cells that play a crucial role in activating other immune cells in autoimmune reactions.
2. Decreased functional activity of T-suppressors (Choice A) is typical in autoimmune reactions as it leads to unchecked immune responses.
3. Loss of tolerance for T-helpers and B-lymphocytes (Choice B) is common in autoimmune reactions, where the immune system mistakenly attacks self-cells.
4. Ag released by normally isolated tissues (Choice C) is a typical mechanism in autoimmune reactions where self-antigens trigger immune responses.
The main function of siderophores in bacteria is:
- A. to enhance antibiotic resistance
- B. to sequester iron from the environment
- C. to form capsules
- D. to perform oxidative phosphorylation
Correct Answer: B
Rationale: The correct answer is B: to sequester iron from the environment. Siderophores are molecules produced by bacteria to chelate and acquire iron, an essential nutrient for their growth and survival. By sequestering iron, bacteria can compete with host cells and other microbes for this vital resource. This enhances their ability to thrive and establish infections. Choices A, C, and D are incorrect because siderophores do not directly enhance antibiotic resistance, form capsules, or perform oxidative phosphorylation. These functions are unrelated to the primary role of siderophores in iron acquisition.