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A patient with a sore throat and fever had a throat smear stained with Gram's method, revealing Gram-positive cocci in chains. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Neisseria gonorrhoeae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This bacterium is known to cause sore throat and fever, commonly referred to as strep throat. Gram's stain showing Gram-positive cocci in chains is characteristic of Streptococcus species. Streptococcus pyogenes is a beta-hemolytic bacterium that forms chains and is a common cause of bacterial pharyngitis. Staphylococcus aureus (B) is a Gram-positive cocci that forms clusters, not chains. Neisseria gonorrhoeae (C) is a Gram-negative diplococcus and is not associated with sore throat. Enterococcus faecalis (D) is a Gram-positive cocci that can cause infections but is not typically associated with sore throat.
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Cells that contain a nucleus are __________ cells.
- A. prokaryotic
- B. eukaryotic
- C. anucleate
- D. haploid
Correct Answer: B
Rationale: The correct answer is B: eukaryotic. Eukaryotic cells have a well-defined nucleus that encloses the genetic material. The nucleus is a distinguishing feature of eukaryotic cells, separating them from prokaryotic cells (choice A) which lack a nucleus. Anucleate cells (choice C) are cells that do not have a nucleus at all. Haploid cells (choice D) contain a single set of chromosomes, but this does not necessarily imply the presence of a nucleus. Therefore, the presence of a nucleus is what categorizes cells as eukaryotic.
A patient presented with gas gangrene. Gram-positive rods producing spores and gas were isolated from a wound sample. Identify the microorganism.
- A. Clostridium perfringens
- B. Clostridium tetani
- C. Bacillus anthracis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. Clostridium perfringens is known to cause gas gangrene and is a Gram-positive rod that produces spores and gas in tissue infections. Clostridium tetani causes tetanus, not gas gangrene. Bacillus anthracis causes anthrax, not gas gangrene. Staphylococcus aureus is a Gram-positive cocci and does not produce spores or gas in the context of gas gangrene. Therefore, based on the characteristics of the microorganism isolated from the wound sample, Clostridium perfringens is the most likely causative agent.
What is the best therapeutic plan for treating actinomycosis?
- A. Awaiting self-clearance
- B. Only antibiotic therapy
- C. Only surgical treatment
- D. Chemotherapy combined with surgical therapy
Correct Answer: D
Rationale: The correct answer is D, chemotherapy combined with surgical therapy. Actinomycosis is a bacterial infection that requires a combination of antibiotics to target the bacteria and surgery to remove abscesses or infected tissues. Antibiotics alone may not penetrate abscesses effectively. Waiting for self-clearance can lead to complications. Surgical treatment alone may not eradicate the infection entirely. Therefore, the most effective therapeutic plan is to combine chemotherapy to treat the infection systemically and surgery to remove localized infections.
Which of the following does NOT refer to viruses
- A. cell-free infectious living systems
- B. obligate intracellular parasites
- C. they have either DNA or RNA as genetic material
- D. they are not sensitive to interferon
Correct Answer: D
Rationale: The correct answer is D because viruses are sensitive to interferon, a natural defense mechanism of the body against viral infections. Interferon helps to inhibit viral replication.
A: Viruses are cell-free infectious particles, not living systems.
B: Viruses are obligate intracellular parasites as they require host cells to replicate.
C: Viruses can have either DNA or RNA as genetic material, which is a characteristic feature.
For the structure of rubella virus, it is true that
- A. has icosahedral type of symmetry
- B. is ssDNA virus
- C. does not have an envelope
- D. does not have glycoprotein spikes
Correct Answer: A
Rationale: Step 1: Rubella virus belongs to the Togaviridae family, which typically exhibits icosahedral symmetry.
Step 2: Icosahedral symmetry refers to a structure with 20 equilateral triangular faces, which is characteristic of many viruses, including rubella.
Step 3: Therefore, choice A is correct as rubella virus indeed has icosahedral type of symmetry.
Summary:
- Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA.
- Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane.
- Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface.