All of the following viruses are enveloped EXCEPT:
- A. Hepatitis C virus
- B. Hepatitis B virus
- C. Hepatitis A virus
- D. Hepatitis D virus
Correct Answer: C
Rationale: The correct answer is C: Hepatitis A virus. This is because Hepatitis A virus is a non-enveloped virus, while choices A, B, and D are all enveloped viruses. Enveloped viruses have a lipid bilayer membrane surrounding their protein capsid, aiding in their ability to infect host cells. Hepatitis C, B, and D viruses all possess this lipid envelope, making them enveloped viruses. Hepatitis A virus, on the other hand, lacks this lipid envelope and is classified as a non-enveloped virus. Therefore, the correct answer is C.
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A patient with severe abdominal pain and vomiting had a blood culture that revealed Gram-negative rods producing gas. What is the most likely causative agent?
- A. Escherichia coli
- B. Salmonella enteritidis
- C. Clostridium perfringens
- D. Campylobacter jejuni
Correct Answer: B
Rationale: The correct answer is B: Salmonella enteritidis. In this case, the presence of Gram-negative rods producing gas in the blood culture indicates a likelihood of Salmonella infection, as it is a common cause of severe abdominal pain, vomiting, and gas production. Salmonella enteritidis is a known pathogen that can cause gastroenteritis and systemic infections. Escherichia coli (choice A) can also cause similar symptoms, but it is less likely to produce gas in blood culture. Clostridium perfringens (choice C) typically causes food poisoning with rapid onset and less likely to be isolated from blood cultures. Campylobacter jejuni (choice D) is associated with gastroenteritis but is less likely to cause systemic infections with gas-producing Gram-negative rods in blood culture.
A patient presented with gas gangrene. Gram-positive rods producing spores and gas were isolated from a wound sample. Identify the microorganism.
- A. Clostridium perfringens
- B. Clostridium tetani
- C. Bacillus anthracis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. Clostridium perfringens is known to cause gas gangrene and is a Gram-positive rod that produces spores and gas in tissue infections. Clostridium tetani causes tetanus, not gas gangrene. Bacillus anthracis causes anthrax, not gas gangrene. Staphylococcus aureus is a Gram-positive cocci and does not produce spores or gas in the context of gas gangrene. Therefore, based on the characteristics of the microorganism isolated from the wound sample, Clostridium perfringens is the most likely causative agent.
For the structure of rubella virus, it is true that
- A. has icosahedral type of symmetry
- B. is ssDNA virus
- C. does not have an envelope
- D. does not have glycoprotein spikes
Correct Answer: A
Rationale: Step 1: Rubella virus belongs to the Togaviridae family, which typically exhibits icosahedral symmetry.
Step 2: Icosahedral symmetry refers to a structure with 20 equilateral triangular faces, which is characteristic of many viruses, including rubella.
Step 3: Therefore, choice A is correct as rubella virus indeed has icosahedral type of symmetry.
Summary:
- Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA.
- Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane.
- Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface.
For prevention of tuberculosis is used
- A. specific anti-tuberculosis serum
- B. BCG
- C. DTP
- D. PPD
Correct Answer: B
Rationale: The correct answer is B: BCG. Bacille Calmette-Guérin (BCG) vaccine is used for the prevention of tuberculosis. BCG is a live attenuated strain of Mycobacterium bovis that helps the immune system recognize and fight off tuberculosis bacteria. Specific anti-tuberculosis serum (A) is not used for prevention but for treatment. DTP (C) stands for diphtheria, tetanus, and pertussis vaccine, not specific for tuberculosis prevention. PPD (D) is a tuberculin skin test used for diagnosis, not prevention. Thus, BCG is the correct choice for tuberculosis prevention.
Lytic life cycle of phages does not include
- A. germination
- B. penetration
- C. adsorption
- D. lysis
Correct Answer: A
Rationale: The correct answer is A: germination. In the lytic life cycle of phages, germination is not a stage. The lytic cycle involves adsorption, penetration, replication, assembly, and lysis. Germination is typically associated with the lysogenic cycle, where the phage DNA integrates into the host genome. Therefore, A is the correct answer. Choices B, C, and D are incorrect because they are all stages of the lytic cycle. Penetration refers to the injection of phage DNA into the host cell, adsorption is the attachment of the phage to the host cell, and lysis is the final stage where the host cell bursts, releasing new phages.