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Which bacteria is known for producing an exotoxin that causes severe diarrhea?
- A. Vibrio cholerae
- B. Clostridium botulinum
- C. Streptococcus pyogenes
- D. Salmonella enterica
Correct Answer: A
Rationale: Rationale: Vibrio cholerae produces the exotoxin responsible for severe diarrhea. It causes cholera by disrupting the normal functioning of the intestines. Clostridium botulinum causes botulism, not diarrhea. Streptococcus pyogenes causes strep throat and skin infections. Salmonella enterica causes food poisoning, not severe diarrhea. Therefore, the correct answer is A.
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A smear from frothy and purulent vaginal discharges of a 42 y.o. woman was stained by Romanovsky-Giemsa method. Its analysis revealed some microorganisms of flagellates class. What microorganism were the most probably revealed?
- A. Trichomonas vaginalis
- B. Leishmania donovani
- C. Trypanosoma gambiense
- D. Trihomonas hominis
Correct Answer: A
Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a flagellated protozoan that causes trichomoniasis, a sexually transmitted infection commonly found in vaginal discharges. In this case, the presence of flagellates in the vaginal discharge aligns with the characteristics of Trichomonas vaginalis. Leishmania donovani causes leishmaniasis, transmitted by sandflies. Trypanosoma gambiense causes African sleeping sickness through the tsetse fly bite. Trihomonas hominis is a non-pathogenic flagellate found in the human intestine. Therefore, the correct choice is A due to the correlation between the flagellates found in the vaginal discharge and the characteristics of Trichomonas vaginalis.
A patient has been hospitalized with provisional diagnosis of botulism. What serological reaction should be used to reveal botulinum toxin?
- A. Neutralization reaction
- B. Agglutination reaction
- C. Bordet-Gengou test
- D. Precipitation reaction
Correct Answer: A
Rationale: The correct answer is A: Neutralization reaction. This is the most appropriate serological test to reveal botulinum toxin because it involves mixing the patient's serum with known botulinum antitoxin. If the patient's serum contains botulinum toxin, it will neutralize the antitoxin, leading to a lack of toxin-neutralizing ability. The other choices are incorrect because agglutination reaction involves clumping of cells, not suitable for detecting botulinum toxin; Bordet-Gengou test is used to detect antibodies in pertussis infection, not botulinum toxin; and precipitation reaction involves the formation of a solid when two solutions are mixed, not ideal for detecting botulinum toxin.
A microscope that provides a three-dimensional image of a specimen is a
- A. dark-field microscope
- B. transmission electron microscope
- C. bright-field microscope
- D. scanning electron microscope
Correct Answer: D
Rationale: The correct answer is D: scanning electron microscope. A scanning electron microscope provides a three-dimensional image of a specimen by scanning a focused electron beam across the surface of the specimen, detecting the electrons that are emitted from the surface, and creating a detailed image. This is achieved through the detection of secondary electrons, backscattered electrons, and X-rays emitted from the specimen surface.
A dark-field microscope (choice A) utilizes oblique lighting to enhance contrast and is not specifically designed to provide a 3D image. A transmission electron microscope (choice B) uses a beam of electrons transmitted through a specimen to create a 2D image at high magnification. A bright-field microscope (choice C) is a basic microscope that illuminates a specimen with uniform light and does not provide a 3D image like a scanning electron microscope does.
Influenza Viruses cannot be isolated in:
- A. Laboratory Animals
- B. Embryonated eggs
- C. Cell cultures
- D. Agar media
Correct Answer: D
Rationale: The correct answer is D: Agar media. Influenza viruses cannot be isolated in agar media because they require specific conditions present in laboratory animals, embryonated eggs, or cell cultures for successful isolation and propagation. Agar media lack the necessary components and environment needed for influenza virus replication. In laboratory animals, such as mice, the viruses can replicate and cause infection. Embryonated eggs provide a suitable environment for influenza virus growth and isolation due to the presence of necessary nutrients and factors. Cell cultures offer controlled conditions for virus propagation and study, making them a valuable tool in influenza virus research.
Which one of the following growth media is used to cultivate Mycobacterium tuberculosis?
- A. Lowestein-Jensen
- B. Loefllers's
- C. All of the above
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Lowestein-Jensen. This is because Lowestein-Jensen medium is specifically designed to cultivate Mycobacterium tuberculosis, providing necessary nutrients and conditions for its growth. Loefller's medium is not optimal for cultivating M. tuberculosis. Choice C (All of the above) is incorrect as not all the options listed are suitable for cultivating M. tuberculosis. Choice D (None of the above) is also incorrect as Lowestein-Jensen is indeed the recommended growth medium for this bacterium.