The causative agent of syphilis is:
- A. Borrelia burgdorferi
- B. Treponema pallidum
- C. Leptospira interrogans
- D. Rickettsia rickettsii
Correct Answer: B
Rationale: The correct answer is B: Treponema pallidum.
1. Treponema pallidum is a spirochete bacterium known to cause syphilis.
2. Borrelia burgdorferi causes Lyme disease, not syphilis.
3. Leptospira interrogans causes leptospirosis, not syphilis.
4. Rickettsia rickettsii causes Rocky Mountain spotted fever, not syphilis.
Therefore, Treponema pallidum is the causative agent of syphilis, making it the correct answer.
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A 16-year-old boy from the rural area entered the technical school. During a regular Mantoux test, it turned out that this boy had a negative reaction. What tactics should the doctor choose as the most rational in this case?
- A. Repeat the test in a month
- B. Serodiagnosis of tuberculosis
- C. Urgent isolation of the boy from his groupmates
- D. BCG vaccination
Correct Answer: D
Rationale: The correct answer is D: BCG vaccination. BCG vaccination is recommended for individuals with a negative Mantoux test result, especially in countries where tuberculosis is prevalent. This vaccination can help provide protection against tuberculosis.
Choice A is incorrect because repeating the Mantoux test in a month is unnecessary since the boy already had a negative reaction.
Choice B is incorrect as serodiagnosis of tuberculosis is not the first-line approach for diagnosis, especially in this scenario.
Choice C is incorrect because urgent isolation is not necessary based solely on the Mantoux test result. Isolation is typically reserved for individuals with active tuberculosis.
What is the most appropriate method for diagnosis of listeriosis
- A. cultivating on artificial media and biochemical identification
- B. serological diagnosis with ELISA
- C. serological diagnosis with agglutination hype Widal
- D. cultivating in cell cultures
Correct Answer: A
Rationale: The correct answer is A: cultivating on artificial media and biochemical identification. This method is appropriate for diagnosing listeriosis because it allows for the isolation and growth of Listeria species on selective media, followed by biochemical tests to confirm the identity. Serological diagnosis with ELISA (choice B) is not as specific for Listeria and may yield false positives. Choice C, serological diagnosis with agglutination hype Widal, is not typically used for listeriosis diagnosis. Cultivating in cell cultures (choice D) is not the primary method for diagnosing listeriosis as it is less specific compared to cultivating on artificial media and biochemical identification.
Lytic cycle of the bacteriophages differs from the lysogenic one by
- A. lysogenetic phages destroy the host cell when leaving the cell
- B. lytic phages do not destroy the host cell
- C. do not differ
- D. none of them
Correct Answer: A
Rationale: The correct answer is A because in the lytic cycle, the bacteriophage destroys the host cell upon release, whereas in the lysogenic cycle, the phage integrates its DNA into the host genome without killing the host immediately. This integration may lead to the destruction of the host cell at a later stage. Choice B is incorrect as lytic phages do destroy the host cell. Choice C is incorrect as the two cycles have distinct mechanisms. Choice D is incorrect as there are clear differences between the lytic and lysogenic cycles.
A patient with pulmonary tuberculosis is prescribed the most effective antituberculosis antibiotic. Name this drug:
- A. Tetracycline
- B. Furasolidone
- C. Rifampicin
- D. Bactrim (Co-trimoxazole)
Correct Answer: C
Rationale: Rifampicin is the correct answer because it is a first-line antibiotic for treating pulmonary tuberculosis. It has excellent bactericidal activity and penetrates well into lung tissues where the infection is located. Rifampicin is also known for preventing the development of resistance. Tetracycline (A) and Furasolidone (B) are not commonly used for tuberculosis treatment. Bactrim (D) is a combination of sulfamethoxazole and trimethoprim, not effective for tuberculosis treatment.
Viral capsomeres are composed of subunits called
- A. envelopes.
- B. protomeres.
- C. capsids.
- D. nucleoids.
Correct Answer: B
Rationale: The correct answer is B: protomeres. Viral capsomeres are the building blocks of viral capsids, which are protein coats that enclose and protect the viral genetic material. These capsomeres are made up of smaller subunits called protomeres. Envelopes (A) refer to a lipid membrane surrounding some viruses, not the subunits of capsomeres. Capsids (C) are the protein coats that capsomeres make up, not the subunits themselves. Nucleoids (D) are found in bacterial cells and refer to the region where the genetic material is located, not the subunits of viral capsomeres.