Nokea
Among public catering workers examined by doctors of sanitary and epidemiologic station often occur asymptomatic parasite carriers. This means that a healthy person carries cysts that infect other people. Such parasitizing is possible for the following causative agent:
- A. Dysenteric amoeba
- B. Malarial plasmodium
- C. Intestinal trichomonad
- D. Dermatotropic leishmania
Correct Answer: A
Rationale: Rationale:
1. Dysenteric amoeba (Choice A) is the correct answer because it can exist asymptomatically in carriers and be transmitted through cysts.
2. Malarial plasmodium (Choice B) causes malaria, not carried asymptomatically in cysts.
3. Intestinal trichomonad (Choice C) causes trichomoniasis, not carried asymptomatically in cysts.
4. Dermatotropic leishmania (Choice D) causes skin lesions, not carried asymptomatically in cysts.
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The bacitracin sensitivity test demonstrates
- A. staphylococci
- B. pneumococci
- C. intestinal bacteria
- D. group A streptococci
Correct Answer: D
Rationale: The bacitracin sensitivity test is used to differentiate between different types of streptococci. Group A streptococci are sensitive to bacitracin, which means they will show inhibition around the bacitracin disk. This sensitivity is a characteristic feature of group A streptococci and helps in their identification. Staphylococci, pneumococci, and intestinal bacteria do not exhibit this sensitivity to bacitracin. Therefore, the correct answer is D: group A streptococci.
Bacterial spores are resistant to harsh conditions due to:
- A. their lipid-rich membranes
- B. presence of calcium dipicolinate
- C. rapid metabolism
- D. high water content
Correct Answer: B
Rationale: The correct answer is B because the presence of calcium dipicolinate in bacterial spores helps protect their DNA from damage under harsh conditions. Calcium dipicolinate acts as a stabilizer, preserving the spore structure.
Choice A is incorrect as bacterial spores have a tough protein coat, not a lipid-rich membrane. Choice C is incorrect as bacterial spores have very low metabolic activity. Choice D is incorrect as bacterial spores have low water content to prevent damage during harsh conditions.
A saucer-shaped liquefaction in a gelatin stab is referred to as:
- A. napiform
- B. saccate
- C. crateriform
- D. stratiform
Correct Answer: C
Rationale: The correct answer is C: crateriform. In a gelatin stab, a saucer-shaped liquefaction indicates a depression or crater-like shape. This term accurately describes the appearance of the liquefaction.
A: napiform means turnip-shaped, which is not relevant to the shape in a gelatin stab.
B: saccate means pouch-like, which does not match the saucer-shaped description.
D: stratiform refers to something in layers, which is not applicable to the shape of the liquefaction.
Therefore, C is the most appropriate term to describe the saucer-shaped liquefaction in a gelatin stab.
Which ones of the following symptoms are not typical of botulism:
- A. Dry mouth and difficulty in swallowing and speaking
- B. Blurred vision, diplopia
- C. Descending, flaccid paralysis
- D. Chills, fever up to 40°C and loss of consciousness
Correct Answer: D
Rationale: The correct answer is D. Botulism typically presents with symptoms such as dry mouth, difficulty swallowing, blurred vision, diplopia, and descending flaccid paralysis. Chills, fever, and loss of consciousness are not typical of botulism. Botulism is caused by a neurotoxin produced by Clostridium botulinum bacteria, which affects the nervous system leading to muscle weakness and paralysis, not fever or altered consciousness. Therefore, choice D is the correct answer.
Which of the following statements regarding the antigenic shift is NOT true?
- A. It is due to exchange of genetic information between animal and human influenza A virus
- B. It is due to the direct passage in the human population of animal or avian influenza viruses of type A
- C. It is due to the recirculation of a previously circulating influenza strain
- D. It is due to dot mutations that are the base of small antigenic changes
Correct Answer: D
Rationale: The correct answer is D because antigenic shift is a major change in the influenza virus where genetic material from different influenza viruses mix to create a new subtype. This is a large-scale change that results in a novel virus with a different antigenic composition. Option A and B are incorrect because antigenic shift does involve the exchange of genetic information between animal and human influenza A viruses, and it does occur when animal or avian influenza viruses of type A directly pass into the human population. Option C is incorrect because antigenic shift is not related to the recirculation of a previously circulating influenza strain.