Nokea
Rotaviruses:
- A. The NSP4 nonstructural protein of rotaviruses acts in a toxic-like manner.
- B. Disease can be significant in infants and adults
- C. Cannot survive the acidic environment in the stomach
- D. Prevents the absorption of water, but do not cause a net secretion of water and loss of ions
Correct Answer: A
Rationale: The correct answer is A because the NSP4 nonstructural protein of rotaviruses indeed acts in a toxic-like manner by disrupting calcium homeostasis, leading to diarrhea. Choice B is incorrect as rotaviruses can cause significant disease in infants, but not typically in adults. Choice C is incorrect as rotaviruses are resistant to stomach acid. Choice D is incorrect as rotaviruses cause a net secretion of water and loss of ions, contributing to diarrhea.
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A child is ill with diphtheria. A smear of the affected mucous membrane revealed blue rods with thickenings at the poles. What staining method was used?
- A. Neisser
- B. Gram
- C. Ziehl-Neelsen
- D. Loeffler
Correct Answer: A
Rationale: The correct answer is A: Neisser staining method. Neisser staining method is used to stain diphtheria bacilli, which appear as blue rods with thickenings at the poles. The rationale is that Neisser staining specifically targets and highlights the characteristics of the diphtheria bacilli.
Incorrect choices:
B: Gram staining is not specific for diphtheria bacilli and does not show the characteristic blue rods with thickenings at the poles.
C: Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for diphtheria bacilli.
D: Loeffler staining is used for diphtheria bacilli but does not produce blue rods with thickenings at the poles as seen in this case.
Which of the following microorganisms can be cultured only in the footpads of mice or a species of armadillo?
- A. Mycobacterium tuberculosis
- B. Mycobacterium leprae
- C. Neisseria gonorrhoeae
- D. Mycoplasma
Correct Answer: B
Rationale: The correct answer is B: Mycobacterium leprae. This microorganism can only be cultured in the footpads of mice or a species of armadillo due to its specific growth requirements. Mycobacterium tuberculosis (choice A) can be cultured in various culture media in the laboratory. Neisseria gonorrhoeae (choice C) can be cultured on selective media like Thayer-Martin agar. Mycoplasma (choice D) can be cultured in cell cultures or specialized media. Therefore, the unique growth pattern of Mycobacterium leprae makes it the correct answer.
A woman delivered a dead child with multiple developmental defects. What protozoan disease might have caused the intrauterine death?
- A. Toxoplasmosis
- B. Leishmaniasis
- C. Malaria
- D. Amebiasis
Correct Answer: A
Rationale: The correct answer is A: Toxoplasmosis. Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii, which can be transmitted from mother to fetus during pregnancy, leading to congenital toxoplasmosis. This infection can result in stillbirth, multiple developmental defects, and intrauterine death. Leishmaniasis (B), Malaria (C), and Amebiasis (D) are caused by different parasites and do not typically lead to intrauterine death or developmental defects in the fetus.
Sanitary important bacteria for control of air quality are:
- A. Alpha and beta-hemolytic streptococci
- B. Pseudomonas aeruginosa
- C. E. Coli
- D. Salmonella spp.
Correct Answer: B
Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is important for controlling air quality as it can degrade a wide range of organic compounds present in the air, helping to maintain a clean and healthy environment. Alpha and beta-hemolytic streptococci (Choice A) are not typically associated with air quality control. E. coli (Choice C) and Salmonella spp. (Choice D) are more commonly found in water and food sources, not air, making them incorrect choices for this question. Pseudomonas aeruginosa's ability to break down organic matter in the air makes it the most suitable option for maintaining sanitary air quality.
For measles virus is true that:
- A. There is no outer membrane
- B. Contains singles-stranded RNA with negative polarity
- C. Belongs to family Togaviridae
- D. Cannot be grown on cell cultures
Correct Answer: B
Rationale: The correct answer is B: Contains single-stranded RNA with negative polarity. Measles virus is an enveloped virus with a single-stranded RNA genome that is negative-sense. This means it must first be transcribed into positive-sense RNA before it can be translated. Choice A is incorrect as the measles virus does have an outer envelope. Choice C is incorrect as measles virus belongs to the family Paramyxoviridae, not Togaviridae. Choice D is incorrect as measles virus can be grown on cell cultures, specifically on Vero cells.