Nokea
Etiological factors for the infectious diseases are often microorganisms with various ultrastructure. Which of the following microorganism groups relates to the eukaryotes?
- A. Protozoa
- B. Viruses
- C. Viroids
- D. Prions
Correct Answer: A
Rationale: The correct answer is A: Protozoa. Protozoa are eukaryotic microorganisms, meaning they have a true nucleus and membrane-bound organelles. This relates to the question as eukaryotes are organisms with complex cells containing these features. Viruses (B) are non-living entities that require a host cell to replicate, lacking cellular structures. Viroids (C) are smaller than viruses and consist of only RNA, lacking a protein coat. Prions (D) are misfolded proteins causing diseases but are not considered microorganisms nor do they have cellular structure. Thus, protozoa are the only eukaryotic microorganism group among the options.
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The First-line tuberculosis drugs include:
- A. Isoniazid and rifampicin
- B. Penicillin and erythromycin
- C. Trimethoprim and third generation cephalosporins
- D. All the listed above can be used depending on their resistance profile
Correct Answer: A
Rationale: The correct answer is A: Isoniazid and rifampicin. These drugs are considered first-line treatment for tuberculosis due to their high efficacy and low toxicity. Isoniazid targets the cell wall of the tuberculosis bacteria, while rifampicin inhibits RNA synthesis. They are recommended by WHO as the first choice for treating tuberculosis.
Choice B (Penicillin and erythromycin) is incorrect because these antibiotics are not effective against tuberculosis bacteria.
Choice C (Trimethoprim and third generation cephalosporins) is incorrect because they are not considered first-line drugs for tuberculosis treatment.
Choice D (All the listed above can be used depending on their resistance profile) is incorrect because only isoniazid and rifampicin are universally recognized as first-line drugs for tuberculosis regardless of resistance profile.
Penicillin-resistant, beta-lactamase-producing strains must be detected..
- A. After antibiotic therapy is begun
- B. Before antibiotic therapy is begun
- C. During the antibiotic therapy
- D. No importance for the time of detection
Correct Answer: B
Rationale: The correct answer is B: Before antibiotic therapy is begun. Detecting penicillin-resistant, beta-lactamase-producing strains before antibiotic therapy is crucial to ensure proper treatment. If detected after therapy (choice A), it may lead to treatment failure. Detection during therapy (choice C) may result in delayed or ineffective treatment. Choice D is incorrect as early detection is essential for successful management.
The causative agent of the disease gas gangrene Clostridium perfringens is:
- A. Gram-negative rod-shaped bacteria, fixed with capsule
- B. Gram-negative rod-shaped bacterium, motile, peritrichous without capsule
- C. Gram-positive rod-shaped bacterium, motile, peritrichous without capsule
- D. Gram-positive rod-shaped bacterium non-motile, with capsule
Correct Answer: C
Rationale: The correct answer is C because Clostridium perfringens is a Gram-positive rod-shaped bacterium, which matches the description provided. It is motile and peritrichous (having flagella all over the surface) without a capsule. This bacterium is known to cause gas gangrene due to its ability to produce toxins that destroy tissue.
Choice A is incorrect because Clostridium perfringens is Gram-positive, not Gram-negative, and it does not have a capsule. Choice B is incorrect because Clostridium perfringens is not motile and does not have flagella all over its surface. Choice D is incorrect because Clostridium perfringens is Gram-positive, not Gram-negative, and it is motile without a capsule.
A scientist identifies a strand of RNA that can be directly used to code for important viral proteins during viral replication. What have they found?
- A. RNA major
- B. -RNA
- C. (+RNA)
- D. RNA minor
Correct Answer: C
Rationale: The correct answer is C: (+RNA). This indicates that the scientist found a positive-sense RNA strand that can be directly translated by host cell machinery to produce viral proteins. Positive-sense RNA can act as messenger RNA, allowing immediate protein synthesis during viral replication. Choice A (RNA major) and D (RNA minor) are not standard terms used to describe RNA strands in virology. Choice B (-RNA) indicates a negative-sense RNA strand, which requires transcription to form a complementary positive-sense strand before protein synthesis. Thus, the identification of a strand of RNA that directly codes for viral proteins aligns with the characteristics of a positive-sense RNA strand.
The Gram stain is used to differentiate bacteria based on:
- A. Cell shape
- B. Cell wall structure
- C. Flagella composition
- D. Nutrient requirements
Correct Answer: B
Rationale: The Gram stain differentiates bacteria based on cell wall structure. It classifies bacteria into Gram-positive (purple) and Gram-negative (pink) based on the presence of peptidoglycan in the cell wall. This method helps in identifying the bacterial species and determining appropriate treatment. Option A (Cell shape) is incorrect because the Gram stain focuses on cell wall composition, not cell shape. Option C (Flagella composition) is incorrect as the Gram stain does not assess flagella. Option D (Nutrient requirements) is incorrect as it does not relate to the purpose of the Gram stain.