Nokea
Microscopic examination of dental plaque revealed unicellular organisms with two layers in their cytoplasm and wide pseudopodia. What is the likely causative agent?
- A. Entamoeba gingivalis
- B. Entamoeba histolytica
- C. Trichomonas tenax
- D. Lamblia intestinalis
Correct Answer: A
Rationale: Rationale:
1. Unicellular organisms with two layers in cytoplasm = Entamoeba gingivalis.
2. Wide pseudopodia = characteristic of Entamoeba genus.
3. Entamoeba histolytica causes amoebic dysentery, not dental plaque.
4. Trichomonas tenax causes periodontal disease, not dental plaque.
5. Lamblia intestinalis causes giardiasis, not related to dental plaque.
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Which of the following pathogens can cause meningitis?
- A. Staph. aureus
- B. Strep. pyogenes
- C. Strep. pneumoniae
- D. None of the above
Correct Answer: C
Rationale: Rationale for choice C (Strep. pneumoniae):
1. Strep. pneumoniae is a common cause of bacterial meningitis.
2. It is a leading pathogen responsible for meningitis in adults and children.
3. It can invade the bloodstream and reach the meninges, causing inflammation.
4. Treatment guidelines often include antibiotics effective against Strep. pneumoniae.
Summary of why other choices are incorrect:
A. Staph. aureus is not a common cause of meningitis.
B. Strep. pyogenes typically causes streptococcal infections but not meningitis.
D. "None of the above" is incorrect as Strep. pneumoniae can cause meningitis.
The generation time of bacteria refers to:
- A. The time for DNA replication
- B. The time for a cell to divide and double in number
- C. The time for spore formation
- D. The time for toxin production
Correct Answer: B
Rationale: The correct answer is B: The generation time of bacteria refers to the time for a cell to divide and double in number. This is because the generation time is the period required for one bacterial cell to undergo binary fission and divide into two identical daughter cells. This process involves DNA replication, followed by cell division, resulting in an increase in the number of bacterial cells.
Incorrect choices:
A: The time for DNA replication - While DNA replication is a crucial part of bacterial growth and reproduction, it does not solely define the generation time.
C: The time for spore formation - Spore formation is a specific process in certain bacteria and is not synonymous with the generation time.
D: The time for toxin production - Toxin production is an independent process in bacteria and does not directly relate to the generation time.
After a prolonged isoniazid treatment, the patient developed polyneuritis, paresthesia, memory disorders, and convulsions. What is the most likely mechanism of the described isoniazid side-effects?
- A. Disruption of cell membrane synthesis
- B. Inhibition of protein synthesis
- C. Inhibition of RNA-synthesis
- D. Inhibition of pyridoxal phosphate synthesis
Correct Answer: D
Rationale: The correct answer is D. Isoniazid inhibits pyridoxal phosphate synthesis, which is the active form of vitamin B6. Pyridoxal phosphate is essential for various enzymatic reactions, including neurotransmitter synthesis and myelin formation. Therefore, isoniazid-induced pyridoxal phosphate deficiency can lead to neurological symptoms like polyneuritis, paresthesia, memory disorders, and convulsions.
A: Disruption of cell membrane synthesis - This is not the mechanism of isoniazid side-effects.
B: Inhibition of protein synthesis - Isoniazid does not directly inhibit protein synthesis.
C: Inhibition of RNA-synthesis - Isoniazid does not inhibit RNA synthesis; it affects vitamin B6 metabolism.
How would you interpret the study results?
- A. Water is safe to be consumed
- B. Water is of doubtful quality
- C. Water is of highly doubtful quality
- D. Water is contaminated
Correct Answer: D
Rationale: Step-by-step rationale:
1. The study results indicate water contamination.
2. Contaminated water poses health risks.
3. Therefore, the correct interpretation is that water is contaminated.
Summary:
- Choice A is incorrect as safety is not confirmed.
- Choice B is too mild given the severity of contamination.
- Choice C is also incorrect, as it does not accurately reflect the study findings.
Antibiotics are distributed into following groups:
- A. Blockaders of protein synthesis
- B. Blockaders of cell wall synthesis
- C. Alternators of bacterial cytoplasm
- D. Nothing from above
Correct Answer: A
Rationale: The correct answer is A: Blockaders of protein synthesis because antibiotics in this group target bacterial ribosomes, preventing protein synthesis. This disrupts bacterial growth and replication. Choice B is incorrect as cell wall synthesis inhibitors target a different bacterial component. Choice C is incorrect as antibiotics do not alter bacterial cytoplasm. Choice D is incorrect as antibiotics do fall into different categories based on their mechanism of action.