Nokea
All statements of viral neutralization reaction are true except:
- A. A key component of the reaction is the complement system involvement
- B. Specific virus neutralising antibodies block the viral ability to infect cells
- C. The antibodies are titrated and two serum samples are required
- D. It is also used to identify newly isolated virus
Correct Answer: A
Rationale: Rationale:
A: Incorrect - The complement system is not directly involved in the viral neutralization reaction.
B: Correct - Specific antibodies neutralize viruses by blocking their ability to infect cells.
C: Incorrect - Antibodies are titrated, but only one serum sample is required for neutralization testing.
D: Incorrect - Viral neutralization is primarily used to measure antibody response, not to identify newly isolated viruses.
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In Transmissive infections, the vector is:
- A. Air
- B. Objects
- C. Medical devices
- D. Water
Correct Answer: A
Rationale: The correct answer is A: Air. In transmissive infections, the vector refers to the means by which the infectious agent is transmitted from one host to another. Air can carry pathogens such as viruses and bacteria, leading to respiratory infections like the flu or tuberculosis. Airborne transmission occurs when droplets containing the pathogens are inhaled. Objects (B), medical devices (C), and water (D) can also transmit infections, but they are not specifically related to transmissive infections. Objects and medical devices can harbor pathogens, while waterborne infections are transmitted through contaminated water sources. However, in the context of transmissive infections, the primary vector is the air due to its ability to carry infectious agents over distances.
Non-gonococcal urethritis and cervicitis can be caused by
- A. Mycoplasma hominis
- B. Mycoplasma genitalium
- C. Ureaplasma urealyticum
- D. all of them
Correct Answer: D
Rationale: The correct answer is D because Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma urealyticum are all known to cause non-gonococcal urethritis and cervicitis. These organisms can infect the urogenital tract and lead to inflammation and symptoms in both males and females. Each of these bacteria has been identified as a common cause of these conditions through research and clinical studies. Therefore, since all three organisms are capable of causing non-gonococcal urethritis and cervicitis, the correct answer is D. The other choices (A, B, and C) are incorrect because each of them alone can cause these conditions, making option D the most comprehensive and accurate choice.
Which bacteria are Gram-negative cocci?
- A. Neisseria species
- B. Streptococcus species
- C. Bacillus species
- D. Clostridium species
Correct Answer: A
Rationale: The correct answer is A: Neisseria species. Gram staining differentiates bacteria based on cell wall composition. Gram-negative bacteria like Neisseria have a thin peptidoglycan layer and an outer membrane, making them appear pink under the microscope. Streptococcus species (B) are Gram-positive cocci with a thick peptidoglycan layer, appearing purple. Bacillus (C) and Clostridium (D) species are Gram-positive rods, not Gram-negative cocci. Thus, the correct answer is A because Neisseria species are the only Gram-negative cocci among the choices provided.
A patient presents with a history of diarrhea of several weeks' duration. Which of the following may be the cause?
- A. Bordetella pertussis
- B. Yersinia enterocolitica
- C. Corynebacterium diphtheria
- D. Neisseria meningitidis
Correct Answer: B
Rationale: The correct answer is B: Yersinia enterocolitica. Y. enterocolitica is known to cause gastroenteritis and diarrhea in humans. It is often associated with contaminated food or water. Bordetella pertussis causes whooping cough, not diarrhea. Corynebacterium diphtheria causes respiratory diphtheria. Neisseria meningitidis is associated with meningitis and septicemia, not diarrhea. Therefore, based on the patient's symptoms and history, Y. enterocolitica is the most likely cause of the diarrhea in this case.
A smear prepared from material obtained from patient with suspected diphtheria contains yellow bacilli with blue grains at their ends. What staining was used in this case?
- A. Ziehl-Nielsen
- B. Kozlovsky
- C. Romanovsky
- D. Loefler
Correct Answer: D
Rationale: The correct answer is D: Loefler. This staining method is used for identifying Corynebacterium diphtheriae, the causative agent of diphtheria. It involves using methylene blue and basic fuchsin to stain the bacteria. The yellow bacilli with blue grains at their ends indicate the characteristic appearance of C. diphtheriae when stained using the Loefler method.
Choice A: Ziehl-Nielsen is used for acid-fast bacteria like Mycobacterium tuberculosis.
Choice B: Kozlovsky is not a standard staining method in microbiology.
Choice C: Romanovsky is used for blood smears to identify malaria parasites.