Nokea
A centrifugate of urine sample obtained from patient with suspected renal tuberculosis was used to make a slide mount for microscopy. What method should be used to stain the slide and detect the causative agent?
- A. Zielh-Neelsen stain
- B. Loeffler stain
- C. Gram stain
- D. Aujeszky stain
Correct Answer: A
Rationale: The correct answer is A: Zielh-Neelsen stain. This stain is specifically used to detect acid-fast bacteria like Mycobacterium tuberculosis, the causative agent of renal tuberculosis. The staining process involves using carbol fuchsin to penetrate the mycolic acid layer of the bacterial cell wall, making it resistant to decolorization with acid-alcohol. This allows the red stained bacteria to be visualized under a microscope. Loeffler stain (B) is used for staining bacteria like diphtheria bacilli, Gram stain (C) is used for bacterial classification based on cell wall properties, and Aujeszky stain (D) is not a recognized staining method for detecting acid-fast bacteria.
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Which bacteria is responsible for causing tuberculosis?
- A. Mycobacterium tuberculosis
- B. Streptococcus pneumoniae
- C. Salmonella enterica
- D. Neisseria meningitidis
Correct Answer: A
Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis. It is a slow-growing, acid-fast bacillus that primarily affects the lungs. Mycobacterium tuberculosis is transmitted through the air via respiratory droplets. Choice B, Streptococcus pneumoniae, is a common cause of pneumonia but not tuberculosis. Choice C, Salmonella enterica, causes food poisoning. Choice D, Neisseria meningitidis, causes meningitis, not tuberculosis. Therefore, Mycobacterium tuberculosis is the correct answer based on its characteristics and mode of transmission.
An inflammatory disease that can develop as a complication following a group A streptococcal infection is:
- A. endocarditis
- B. rheumatic fever
- C. nephritis
- D. cytomegalovirus
Correct Answer: B
Rationale: The correct answer is B: rheumatic fever. Rheumatic fever is an inflammatory disease that can occur as a complication following a group A streptococcal infection. This is known as a post-streptococcal complication. It typically affects the heart, joints, skin, and brain. Endocarditis (choice A) is also a complication of streptococcal infections, but it is an infection of the heart valves, not an inflammatory disease like rheumatic fever. Nephritis (choice C) is inflammation of the kidneys and is not directly related to streptococcal infections. Cytomegalovirus (choice D) is a different viral infection and is not associated with streptococcal infections.
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.
By precipitation of tuberculin, a purified protein derivative (PPD) is obtained. It is used in:
- A. Mantoux test
- B. Schick test
- C. Dick test
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Mantoux test. The Mantoux test is used to screen for tuberculosis by injecting PPD intradermally. The presence of a delayed hypersensitivity reaction indicates prior exposure to Mycobacterium tuberculosis. The Schick test (B) is used to test for immunity to diphtheria, while the Dick test (C) is used to test for immunity to scarlet fever. Therefore, the correct use of PPD is in the Mantoux test for tuberculosis screening.