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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.
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A child with fever and swollen lymph nodes had a Gram-stained smear revealing Gram-negative rods with a safety pin appearance. 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. This bacterium causes the plague, which presents with fever and swollen lymph nodes. The safety pin appearance on Gram stain is characteristic of Yersinia pestis.
B: Francisella tularensis causes tularemia, which presents differently and does not show safety pin appearance on Gram stain.
C: Brucella abortus causes brucellosis, which does not typically present with the same symptoms as described in the question.
D: Clostridium botulinum causes botulism, which does not show safety pin appearance on Gram stain and does not typically present with fever and swollen lymph nodes.
Which bacteria are most commonly associated with foodborne illnesses?
- A. Salmonella enterica
- B. Escherichia coli
- C. Vibrio cholerae
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all three bacteria (Salmonella enterica, Escherichia coli, Vibrio cholerae) are commonly associated with foodborne illnesses. Salmonella causes gastroenteritis, E. coli can lead to severe food poisoning, and Vibrio cholerae causes cholera. Therefore, choosing "All of the above" encompasses the most common bacteria linked to foodborne illnesses. Choices A, B, and C are incorrect as they do not cover the full range of bacteria typically involved in foodborne illnesses.
The enzyme required for replication of viral RNA is:
- A. Reverse transcriptase
- B. DNA polymerase
- C. RNA-dependent RNA polymerase
- D. Ligase
Correct Answer: C
Rationale: The correct answer is C: RNA-dependent RNA polymerase. This enzyme is required for replicating viral RNA due to its ability to catalyze the synthesis of RNA using an RNA template. Reverse transcriptase (A) is used to transcribe RNA into DNA, not replicate viral RNA. DNA polymerase (B) is used for replicating DNA, not RNA. Ligase (D) is involved in joining DNA fragments, not in replicating viral RNA. Therefore, RNA-dependent RNA polymerase is the only enzyme that specifically performs the function required for replicating viral RNA.
Bacteria that have a single polar flagellum at one end are referred to as:
- A. monotrichous
- B. monotrichous
- C. amphitrichous
- D. peritrichous
Correct Answer: B
Rationale: Step-by-step rationale:
1. Monotrichous means having a single flagellum at one end.
2. The term "polar" indicates that the flagellum is located at one end of the bacterium.
3. Therefore, bacteria with a single polar flagellum are referred to as monotrichous.
4. Choice A is a typo, as it is the same as the correct answer B.
Summary:
- Choice A is a typo, as it duplicates the correct answer.
- Choice C, amphitrichous, refers to bacteria with a flagellum at each end.
- Choice D, peritrichous, describes bacteria with flagella distributed over the entire surface.
Which of the following statements concerning Neisseria Meningitidis is correct?
- A. Has no capsules
- B. It causes epidemic meningitis
- C. Grow on differential media
- D. Gram-positive rods
Correct Answer: B
Rationale: The correct answer is B: It causes epidemic meningitis. Neisseria Meningitidis is a bacterium that can cause meningitis, an infection of the protective membranes covering the brain and spinal cord. This bacterium is known to cause outbreaks or epidemics of meningitis, especially in crowded or close-contact settings. The other choices are incorrect because:
A: Neisseria Meningitidis does have a capsule, which helps it evade the immune system.
C: Neisseria Meningitidis grows on selective media like Thayer-Martin agar, not differential media.
D: Neisseria Meningitidis is a Gram-negative diplococcus, not a Gram-positive rod.