Nokea
The causative agent of plague is:
- A. Bordetella pertussis
- B. Yersinia pestis
- C. Rickettsia prowazekii
- D. Treponema pallidum
Correct Answer: B
Rationale: The correct answer is B: Yersinia pestis. Y. pestis is the causative agent of plague, a serious infectious disease transmitted through fleas. It causes bubonic, pneumonic, and septicemic plague. Bordetella pertussis causes whooping cough, Rickettsia prowazekii causes epidemic typhus, and Treponema pallidum causes syphilis. Y. pestis is the correct answer because it is specifically associated with plague, making the other options incorrect.
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Which of the following is characteristic of Gram-negative bacteria?
- A. Thick peptidoglycan layer
- B. Outer membrane containing lipopolysaccharides
- C. Presence of teichoic acids
- D. Absence of a cell wall
Correct Answer: B
Rationale: The correct answer is B: Outer membrane containing lipopolysaccharides. Gram-negative bacteria have an outer membrane that contains lipopolysaccharides, which are important for protection and pathogenicity. This outer membrane is a unique feature of Gram-negative bacteria and is not present in Gram-positive bacteria, making it a key characteristic.
A: Incorrect because Gram-negative bacteria have a thin peptidoglycan layer compared to Gram-positive bacteria.
C: Incorrect because teichoic acids are a characteristic of Gram-positive bacteria, not Gram-negative bacteria.
D: Incorrect because all bacteria, including Gram-negative bacteria, have a cell wall.
For family Togaviridae is true that
- A. they have helical type of symmetry
- B. they have non-segmented (-)dsRNA
- C. they have non-segmented (+)ssRNA
- D. they are non-enveloped viruses
Correct Answer: C
Rationale: Step 1: Togaviridae is a family of viruses known to have non-segmented (+)ssRNA as their genetic material.
Step 2: The positive sense RNA means that the viral RNA can be directly translated into proteins by host machinery.
Step 3: This RNA genome acts as mRNA, allowing for immediate translation of viral proteins.
Step 4: Therefore, choice C is correct as it accurately describes the genetic nature of Togaviridae.
Summary:
- Choice A is incorrect because Togaviridae viruses do not have helical symmetry.
- Choice B is incorrect because Togaviridae viruses do not have non-segmented (-)dsRNA.
- Choice D is incorrect because Togaviridae viruses are enveloped viruses.
A journalist's body temperature has sharply increased in the morning three weeks after his mission in India, it was accompanied with shivering and bad headache. A few hours later the temperature decreased. The attacks began to repeat in a day. He was diagnosed with tropical malaria. What stage of development of Plasmodium is infective for anopheles-female?
- A. Gametocytes
- B. B.Shizontes
- C. C.Merozoites
- D. E.Sporozoites
Correct Answer: D
Rationale: The correct answer is D: Sporozoites. Sporozoites are the infective stage of Plasmodium for the female Anopheles mosquito. Here's the rationale: After being transmitted to a human host through a mosquito bite, the sporozoites travel to the liver where they mature and reproduce asexually as merozoites (not the infective stage for mosquitoes). The merozoites then infect red blood cells, leading to symptoms like fever, headache, and shivering. During the blood stage, some merozoites develop into male and female gametocytes, which are not infective to mosquitoes. When a mosquito bites an infected person, it ingests gametocytes, which then develop into male and female gametes and fuse to form ookinetes. Ookinetes develop into oocysts in the mosquito's gut, releasing sporozoites that migrate to the salivary glands, ready to infect a new human host when the mosquito bites
For family Rhabdoviridae is true that:
- A. They are enveloped viruses
- B. They cause plague
- C. They have spherical shape
- D. They infect only humans
Correct Answer: A
Rationale: The correct answer is A: They are enveloped viruses. Rhabdoviridae family consists of enveloped viruses, which means they have a lipid envelope surrounding their protein coat. This envelope helps the virus in infecting host cells and evading the immune system. The other choices are incorrect because B: They cause plague is not true as Rhabdoviridae family typically causes diseases like rabies in mammals. C: They have spherical shape is incorrect as rhabdoviruses have a bullet-shaped structure. D: They infect only humans is also incorrect as Rhabdoviridae viruses can infect a wide range of hosts beyond just humans.
Which of the following bacteria produce toxins that can lead to foodborne illnesses?
- A. Clostridium botulinum
- B. Salmonella enterica
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D. Clostridium botulinum produces botulinum toxin, Salmonella enterica produces salmonella toxin, and certain strains of Escherichia coli produce toxins like shiga toxin. These toxins can cause severe foodborne illnesses. Therefore, all of the above bacteria can produce toxins that lead to foodborne illnesses. Choices A, B, and C alone are incorrect because each of these bacteria individually can produce toxins that lead to foodborne illnesses.