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Which of the following consists of DNA viruses?
- A. Parvoviridae
- B. Picornaviridae
- C. Astroviridae
- D. Togaviridae
Correct Answer: A
Rationale: The correct answer is A: Parvoviridae. Parvoviruses are DNA viruses, as their genetic material is composed of DNA. This distinguishes them from RNA viruses like Picornaviridae, Astroviridae, and Togaviridae. Parvoviruses replicate in the host cell nucleus, further confirming their DNA nature. Therefore, based on their DNA composition and replication process, Parvoviridae is the correct choice.
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During the staining of sputum smear of a patient with suspected croupous pneumonia the following reactives and stainers were used: gentian violet solution, Lugol's solution, 960 spiritus and water fuchsin. What method of staining is used in this case?
- A. Leffler's
- B. Gram's
- C. Ziehl-Neelsen's
- D. Neisser's
Correct Answer: B
Rationale: The correct answer is B: Gram's staining method. The rationale for this is as follows: Gentian violet and Lugol's solution are used as primary and mordant stains in the Gram's staining method. Spiritus 960 is used as a decolorizer, and water fuchsin is used as a counterstain. This staining method is commonly used in microbiology to differentiate bacteria into Gram-positive and Gram-negative based on their cell wall characteristics.
A: Leffler's staining method is used for the identification of diphtheria bacilli.
C: Ziehl-Neelsen's staining method is used for acid-fast bacteria like Mycobacterium tuberculosis.
D: Neisser's staining method is used for the identification of Neisseria species.
In summary, the use of specific reactives and stainers in the question indicates the application of the Gram's staining method for bacterial differentiation.
The role of pili in bacteria is:
- A. protection from desiccation
- B. motility
- C. adhesion to surfaces and conjugation
- D. spore formation
Correct Answer: C
Rationale: The correct answer is C: adhesion to surfaces and conjugation. Pili are hair-like structures on the surface of bacteria that help them adhere to surfaces and facilitate the transfer of genetic material during conjugation. This is essential for bacterial survival and reproduction. Choice A is incorrect because protection from desiccation is typically associated with other structures like capsules. Choice B is incorrect as motility in bacteria is usually facilitated by flagella. Choice D is incorrect as spore formation involves the formation of specialized structures, not pili.
A group of Ukrainian tourists returning from Samarqand was bringing with them gerbils. During examination in customs office ulcers were detected on the skin of the animals. What protozoa is the most likely to cause the disease in the animals, if mosquitoes are the carriers?
- A. Leishmania tropica major
- B. Balantidium coli
- C. P. falciparum
- D. T. cruzi
Correct Answer: C
Rationale: Rationale:
1. The presence of ulcers in animals suggests a parasitic infection.
2. Mosquitoes as carriers indicate a protozoan transmitted through insect bites.
3. Among the choices, Plasmodium falciparum causes malaria transmitted by mosquitoes.
4. Leishmania tropica major causes cutaneous leishmaniasis, not ulcers.
5. Balantidium coli causes intestinal infections, not skin ulcers.
6. Trypanosoma cruzi causes Chagas disease, not skin ulcers.
What type of bacteria is responsible for causing tuberculosis?
- A. Mycobacterium tuberculosis
- B. Escherichia coli
- C. Clostridium botulinum
- D. Salmonella enterica
Correct Answer: A
Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis, as it has unique characteristics that allow it to infect the lungs and evade the immune system, leading to a chronic infection. Mycobacterium tuberculosis is a slow-growing, acid-fast bacterium that can survive and replicate within macrophages, causing the characteristic granulomas seen in tuberculosis.
Choice B, Escherichia coli, is a common gut bacterium and is not responsible for tuberculosis. Choice C, Clostridium botulinum, causes botulism, not tuberculosis. Choice D, Salmonella enterica, causes food poisoning, not tuberculosis.
The food preparation process in which not all microorganisms are killed, but the number of microbes capable of spoiling the food or causing disease is reduced, is called
- A. sanitation.
- B. pasteurization.
- C. disinfection.
- D. purification.
Correct Answer: B
Rationale: The correct answer is B: pasteurization. This process involves heating food to a specific temperature to kill harmful bacteria while preserving the flavor and quality of the food. Sanitation (A) refers to maintaining cleanliness to prevent contamination. Disinfection (C) involves killing most, but not all, microbes on surfaces. Purification (D) typically refers to the process of removing impurities, not specifically targeting microbes. In this case, pasteurization best describes the process of reducing harmful microbes in food without completely eliminating all microorganisms.