Nokea
Which of the following bacteria produce a neurotoxin that affects the nervous system?
- A. Clostridium botulinum
- B. Clostridium tetani
- C. Both A and B
- D. None of the above
Correct Answer: C
Rationale: Rationale: Both Clostridium botulinum and Clostridium tetani produce neurotoxins. Botulinum toxin affects the nervous system by blocking neurotransmitter release, causing paralysis. Tetanus toxin affects the nervous system by interfering with neurotransmitter release, leading to muscle stiffness and spasms. Therefore, Choice C is correct. Choices A and B alone are incorrect because they only mention one of the bacteria that produces a neurotoxin. Choice D is incorrect because both bacteria mentioned in Choices A and B produce neurotoxins.
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What structure allows bacteria to exchange genetic material?
- A. Pili
- B. Flagella
- C. Endospores
- D. Capsules
Correct Answer: A
Rationale: The correct answer is A: Pili. Pili are hair-like appendages on the surface of bacteria that facilitate the exchange of genetic material through a process called conjugation. During conjugation, bacteria can transfer plasmids and other genetic material to neighboring bacteria through pili. This allows for the exchange of beneficial traits like antibiotic resistance.
Choice B, Flagella, are involved in bacterial movement and not in genetic material exchange. Choice C, Endospores, are protective structures formed by bacteria in response to harsh conditions, but they are not involved in genetic material exchange. Choice D, Capsules, are protective layers around bacteria that help in adherence to surfaces and evasion of the immune system, but they do not play a role in genetic material exchange.
Bacteriophages reproduce by:
- A. Division
- B. Mitosis
- C. Meiosis
- D. None of them
Correct Answer: D
Rationale: Bacteriophages are viruses that infect bacteria, not living organisms. They do not reproduce through division, mitosis, or meiosis because they lack the cellular machinery for these processes. Instead, bacteriophages replicate by inserting their genetic material into a host bacterium and hijacking its cellular machinery to produce new viral particles. Therefore, the correct answer is D - None of them. Division and mitosis involve cellular division in living organisms, while meiosis is a specialized process for sexual reproduction in eukaryotic organisms, none of which apply to bacteriophages.
In a bacteriological laboratory some bacterial smears had to be stained by Gram's method. For this purpose the following reagents were prepared: gentian violet, Lugol's solution, aqueous fuchsin solution. What other reagent is required?
- A. 96% ethanol
- B. 5% sulfuric acid
- C. Methylene blue solution
- D. Carbolic fuchsin
Correct Answer: A
Rationale: The correct answer is A: 96% ethanol. In Gram's staining method, after applying gentian violet, Lugol's solution, and aqueous fuchsin, the next step is to use a decolorizing agent like 96% ethanol to wash away the excess stain from the Gram-negative bacteria. This step is crucial as it helps differentiate between Gram-positive and Gram-negative bacteria based on their cell wall properties. The other choices are incorrect because sulfuric acid is not used in Gram's staining method, methylene blue is typically used in other staining techniques like the simple stain, and carbolic fuchsin is not a standard reagent in the Gram's staining process.
A patient with fever, enlarged lymph nodes, and bacteremia was diagnosed with plague. The Gram-stained smear revealed bipolar-staining, Gram-negative rods. What is the causative agent?
- A. Yersinia pestis
- B. Francisella tularensis
- C. Brucella abortus
- D. Clostridium botulinum
Correct Answer: A
Rationale: The correct answer is A: Yersinia pestis. Y. pestis is the causative agent of plague, characterized by fever, enlarged lymph nodes, and bacteremia. The bipolar-staining, Gram-negative rods seen on Gram stain are typical of Y. pestis.
Incorrect choices:
B: Francisella tularensis causes tularemia, not plague.
C: Brucella abortus causes brucellosis, not plague.
D: Clostridium botulinum causes botulism, not plague.
In summary, the key features of the patient's presentation and the Gram stain findings align with Yersinia pestis as the correct causative agent of plague.
Which of the following bacteria is capable of producing an endotoxin that can lead to septic shock?
- A. Escherichia coli
- B. Salmonella enterica
- C. Pseudomonas aeruginosa
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above.
1. Escherichia coli can produce endotoxin due to its lipopolysaccharide component.
2. Salmonella enterica also produces endotoxin as part of its cell wall structure.
3. Pseudomonas aeruginosa is known to produce endotoxin as well.
Therefore, all of these bacteria are capable of producing endotoxin, which can trigger an excessive immune response leading to septic shock. Other choices are incorrect because they do not cover all the bacteria mentioned in the question that are capable of producing endotoxin.